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Cereal Processing
Level II
Based on October 2019, Version 2
Occupational standards
Module Title: Operating Milling and Purification
LG Code: IND CRP2 M09 LO (1-3) LG (24-26)
TTLM Code: IND CRP2 TTLM09 20 v1
October, 2020
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Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Table of Contents
LO #1- Prepare the milling and purification equipment for process
operation.................................................................................................... 5
Instruction sheet ..................................................................................................... 5
Information Sheet 1- Confirming material and available stock ................................ 7
Self-check 1 ................................................................................................... 12
Information Sheet 2- Identification of cleaning, maintenance and service ............ 13
requirements ......................................................................................................... 13
Self-Check – 2 ................................................................................................ 21
Information Sheet 3- Defining operation equipment and process ......................... 22
Self-Check – 3 ................................................................................................ 27
Information sheet 4- Adjusting machine components and related attachments .... 28
Self-Check – 4 ................................................................................................ 36
Information sheet 5- Identification of processing and operating parameters ......... 37
Self-Check – 5 ................................................................................................ 42
Information sheet 6- Checking and adjusting equipment performance ................. 43
Self-Check – 6 ................................................................................................ 45
Information Sheet 7- Carrying out pre-start checks .............................................. 46
Self-Check – 7 ...................................................................................................... 48
Operation Sheet 1- Guidelines for correct grain storage ....................................... 49
Operation Sheet 2- Cleaning steps for excess zirconia dust avoidance ............... 50
Operation Sheet 3- Milling machine safe work procedure .................................... 51
Operation Sheet 4– Procedures of mounting feed grinding machine.................... 52
Operation Sheet 5 – Rice milling process ............................................................. 55
Operation Sheet 7 – Pre-operation of milling machine handling techniques ......... 56
LAP Test ........................................................................................................ 57
LG #25 ...................................................................................................... 59
LO #2-Operate and monitor the milling and purification process ......... 59
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Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Instruction sheet ................................................................................................... 59
Information Sheet 1- Workplace information, policies and procedures ................. 61
Self-Check – 1 ................................................................................................ 67
Information Sheet 2- Starting and operating the process ...................................... 68
Self-Check – 2 ................................................................................................ 72
Information Sheet -3 Monitoring equipment variation in operating conditions ....... 73
Self-Check – 3 ................................................................................................ 77
Information Sheet 4 - Identifying variation in equipment operation ....................... 78
Self-Check – 4 ............................................................................................... 81
Information Sheet 5 - Reporting maintenance as per workplace reporting format 81
Self-Check – 5 ................................................................................................ 85
Information Sheet 6 - Monitoring and confirming process specification ................ 86
Self-Check – 6 ................................................................................................ 87
Information Sheet -7 Removing fine bran from semolina and bran product .......... 88
Self-Check – 7 ................................................................................................ 92
Information Sheet 8 - Retuning fine bran product to purification or scratch rolls ... 93
Self-Check – 8 ................................................................................................ 97
Information Sheet 9 - Identifying, rectifying and reporting out-of-specification ...... 98
Product/process outcomes ................................................................................... 98
Self-Check – 9 .............................................................................................. 101
Information Sheet 10 - Maintaining the work area with housekeeping standards 102
Self-Check – 10 ........................................................................................... 105
Information Sheet 11 - Conducting work with environmental standards and ...... 106
legislative requirements ...................................................................................... 106
Self-Check – 11 ............................................................................................ 110
Information Sheet 12 - Maintaining workplace records requirements ................. 111
Self-Check – 12 ........................................................................................... 113
Operation Sheet 1- procedure for grinding the bore of a bushing ....................... 114
Operation Sheet 2- Steps of using cleaning hose and wet cleaning process. .... 115
Operation Sheet 3- Reduction means of dust emissions .................................... 116
LAP Test ...................................................................................................... 116
Demonstration ............................................................................................ 116
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Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
LO #3- Shut down the milling and purification process ...................... 117
Instruction sheet ................................................................................................. 117
Information Sheet 1- Identify shutdown procedures............................................ 118
Self-Check – 12 ........................................................................................... 121
Information Sheet 2- Shut down process with workplace procedures................. 122
Self-Check – 2 ............................................................................................. 125
Information Sheet 3- Identifying and reporting maintenance requirements ......... 127
Self-Check – 3 .............................................................................................. 132
Reference Materials ..................................................................................... 135
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Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
LG #24 LO #1- Prepare the milling and purification equipment for
process operation
Instruction sheet
This learning guide is developed to provide you the necessary information regarding the
following content coverage and topics:
Confirming material and available stock,
Identification of cleaning, maintenance and service requirements,
Defining operation equipment and process,
Adjusting machine components and related attachments,
Identification of processing/operating parameters,
Checking and adjusting equipment performance, and
Carrying out pre-start checks.
This guide will also assist you to attain the learning outcomes stated in the cover page.
Specifically, upon completion of this learning guide, you will be able to:
Confirm material and available stock,
Identify cleaning, maintenance and service requirements,
Define operation equipment and process,
Adjust machine components and related attachments,
Identify of processing/operating parameters,
Check and adjust equipment performance, and
Carry out pre-start checks.
Learning Instructions:
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Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
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October 2019
1. Read the specific objectives of this Learning Guide.
2. Follow the instructions described below.
3. Read the information written in the information Sheets
4. Accomplish the Self-checks
5. Perform Operation Sheets
6. Do the “LAP test”
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Author/Copyright TVET program title- Cereal processing
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October 2019
Information Sheet 1- Confirming material and available stock
1.1 Introduction
Raw materials (ingredients, processing aids, and packaging materials) are the
foundation of finished food products. As such, they must meet regulatory requirements
(safe and legal for your intended use) and your specifications (contribute to the
functionality and quality of your process and product).
1.2 Definitions
The meaning of material requirements planning (MRP): a system for
calculating materials and components needed to manufacture a product.
Introduction materials requirements planning: referred to by the initials MRP,
is a technique which assists a company in the detailed planning of its production.
Recall here that the master production schedule sets out an aggregate plan for
production. MRP translates that aggregate plan into an extremely detailed plan.
Data integrity requirements: MRP is highly dependent on having accurate
information about key inputs, especially demand, inventory and production. If
one or two inputs are inaccurate, errors can be magnified at later stages. Data
integrity and data management are thus essential to effective use of MRP
systems.
The material availability data: The MRP element related data, the required/
requested quantity, the confirmed quantity, the cumulated ATP quantity (quantity
still available after the confirmation is made).
Thus, the importance of raw materials is obvious to those stakeholders that operate
upstream (Figure 1) extracting, refining, and processing material into products; such
stakeholders are intimately aware of the vagaries of material supply and prices.
However, it is critical that all stakeholders become aware of the potential impact of raw
material supplies on their business. In light of this, supply chain stakeholders, should be
aware of the stresses that supply chains place on materials use and the vulnerability of
the supply base for that material to change.
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Cereal processing offers good opportunities for small-scale businesses in Ethiopia
because raw materials are readily available, most equipment is reasonably affordable
and if the products are chosen correctly, they have a good demand and can be
profitable. However, small-scale cereal processors are confronted with strong
competition in the domestic and regional markets. To be profitable it is essential to have
high quality products, an attractive package where appropriate and a well-managed
business.
Figure 1: Supply chain diagram from upstream raw material manufacturer to downstream retail
and reverse supply chain which includes disposal and recycling.
1.3 Quality of raw materials
Poor quality grain is one of the most common problems facing millers and is caused by
inadequate post-harvest control by farmers and inadequate storage conditions in the
mill. Most millers buy their grain from farmers and have little control over the way in
which grain is grown, harvested, stored or transported. Contract agreements with
farmers can improve the amount of control that millers have over the quality of raw
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October 2019
materials. Contracts with farmers Quality assurance in contract growing covers the
following areas:
Correct application of chemicals during cultivation
Harvest at the correct stage of maturity
Correct threshing and winnowing
Adequate drying and post-harvest storage
Correct packaging and transport of grains. Contamination by pesticides and chemical
fertilizers can be due to inadequate information or training for farmers in the amounts of
chemicals to use, or the timing of their application. As part of contract agreements,
millers can prevent such problems by supervising chemical use and checking that
chemical applications are in line with manufacturers’ recommendations. The use of
agricultural chemicals is controlled by law in Ethiopia and millers should check with the
Ministry of Agriculture, Animal Industries and Forestry and the Ethiopian National
Bureau of Standards for details of the specific laws. Millers can also specify or
supervise harvesting to ensure that this is done at the correct stage of maturity and
minimize contamination. Correct post-harvest storage is needed to minimize the risk of
mould growth on grains. Moulds give an unpleasant smell to flour that makes it
unacceptable to consumers and may also damage their health. Some species of
moulds produce poisons in cereals, known as ‘aflatoxins’. These have no taste and may
be eaten by consumers, with the risk of long-term damage to the liver, digestive system
and kidneys.
1.2.1 Guidelines for correct grain storage
Make sure the storeroom is waterproof by locating it on well drained land,
raising it above the ground and fitting a waterproof roof
Prevent the temperature in the store from fluctuating by using insulating
materials (brick, mud, clay, wood or other insulation), painting the outside
white and fitting an overhanging roof to keep sunlight off the walls.
Ensure that the store is insect-proof, rat-proof and bird-proof
Thoroughly clean storerooms by removing and burning all old grain, straw,
insects etc. to prevent contamination of new grain
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Make sure that grain is properly dried before putting it into a store
If chemical insecticides or fungicides are used, ensure that manufacturer’s
recommended dosages are followed.
Regularly check the grain for infestation, signs of mould or discolouration
and ensure that it is not getting hot (each is a sign of excessive moisture).
If these are found, remove the grain and re-dry it.
Most grain is transported in sacks, but the quality of re-used sacks is often not checked.
Dirty sacks contaminate grain and inadequately sealed sacks allow birds, insects and
rodents to contaminate the grain. Control over transport to the mill is part of a quality
assurance scheme and millers should supply good quality sacks for collecting grain and
preferably arrange transport to collect grain directly from the farmers using their own
vehicles, or contracted haulers’ vehicles that have been inspected to ensure that they
are clean. When sacks arrive at the mill, they should be checked to ensure that there
are no holes in the sacks or loose sewing at the top. Sacks should be dry and clean and
not obviously contaminated by oil, grease, kerosene etc. Grain may contain field
contaminants (weed seeds, stalks, soil, stones and dead or living insects), as well as
metal or wood fragments, diesel, oil, etc. from transportation. When the sacks are
opened at the mill, the grain should be spread onto an inspection table checked visually
for:
Contamination by foreign materials
Damage or contamination caused by insects, birds and rodents
Excessive moisture content or mould growth
Broken or immature grains
Foreign materials, mouldy or discoloured grains should be removed by
hand. Some millers also wash grain in a tank to remove sand, small
stones or dust.
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Author/Copyright TVET program title- Cereal processing
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Self-check 1 0Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Choose the best answer (4 point)
1. Contracts with farmers Quality assurance in contract growing covers the following
areas:
A. Correct application of chemicals during cultivation.
B. Harvest at the correct stage of maturity.
C. Correct threshing and winnowing & adequate drying and post-harvest
storage.
D. All .
2. Which one of the following guidelines is not appropriate for correct grain storage?
A. storeroom is shall be waterproof.
B. Properly dried grain needed.
C. Temperature fluctuation is required.
D. Regular checking for infestation.
Test II: Short Answer Questions
1. What does material requirements planning mean? (3points)
2. What is introduction Materials Requirements Planning? (3points)
3. What are the requirements for material requirement planning? (3points)
4. What is material availability date? (3 points)
5. Discuss on supply chain diagram from upstream raw material manufacturer to. (5
points)
6. _________________ referred to by the initials material requirement planning, which
is a technique which assists a company in the detailed planning of its production. (2
points)
You can ask you teacher for the copy of the correct answers
Note: Satisfactory rating - 10 points Unsatisfactory - below 10 points
You can ask you teacher for the copy of the correct answers.
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Information Sheet 2- Identification of cleaning, maintenance and service
requirements
2.1 Building inspection and routine cleaning programmes
Flour dust accumulations attract insects and rodents, which in turn contaminate the
products. It is therefore essential that a monthly inspection be made of floors and walls
for cracks and to ensure that windows and ceiling panels are intact and in place. This
should be part of the job description for a member of staff, who should tick off each
check against a written checklist. The mill owner or manager should ensure that the
checks are properly done.
All spilled grain and flour should be cleaned up at the end of each day’s production
to prevent flour mites and other insects from breeding and contaminating the products.
If infestation is found it should be treated by spot-spraying, but this indicates a failure in
a cleaning programme and changes should be introduced to improve cleaning. Brightly
coloured brooms, brushes and cloths should be used so that any bristles or cloth
fragments to be easily seen if they contaminate the flour.
Fumigants can be used to disinfest grain stores and the following are approved in
Ethiopia: lindane, bromophos, Malathion, dichlorvos, piperonyl butoxide, pyrethrum or
combinations of these. Manufacturer's instructions must be strictly observed and made
available to operators in their language. Methyl bromide gas is now being phased out
under the Montreal Protocol because it destroys the ozone layer.
Process control seed cleaners, dehullers and mills should be checked daily for
loose nuts or bolts and to ensure that settings are correct. Parts that are likely to
wear out should be checked monthly as part of a planned maintenance programme.
Contaminants such as metal fragments, pieces of hardened flour, wire or nylon from
sieves or cotton fibres from sacks can each contaminate flour during milling. Sieves
should be used at points throughout the process to collect larger contaminants and
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October 2019
checked regularly. Contaminants should be recorded and any sudden increase, which
indicates that a problem has arisen, should be investigated and corrective action taken.
Magnets remove any ferrous (iron and steel) metal fragments from grain or flour.
Permanent magnets are preferred because electromagnets can drop an accumulated
mass of filings into the flour if the power fails. Magnets cannot pick up nonferrous
metals and these must be checked for by visual inspection.
Seed cleaners/Winnowers
At its simplest, a seed cleaner is a mesh table on which grain can be spread out and
examined. Dust and small stones fall through the holes in the table and larger leaves,
stalks, mouldy grains etc. can be picked out. Mechanized cleaners consist of an inclined
vibrating flat screen (Figure 1). Grain is fed onto the screen and the vibration assists in
separating the contaminants. These machines cause considerable dust and should be
located in an area where dust can be prevented from contaminating other equipment or
products. They should be cleaned daily by brushing out dust and contaminants. When it
is necessary to wash grain to remove dust and other contaminants, this is done using a
trough or tank containing clean water and fitted with a drain tap so that water can be
regularly replaced. Iron fragments are removed from the grain using permanent
magnets, (electromagnets are not recommended because of the risk of power failures,
which would cause the magnet to drop the collected iron filings into the grain). Other
types of metal particles must be removed by hand on the inspection table.
Figure1. Here next also an example of diagrammatical cereal mill cleaning methods:
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Water system
Change the water at least once a week or when prompted by the system after 240
minutes wet machining time.
Add 75ml Dentate to the tank
Fill the tank with water until the filter(s) is/are completely immersed (up to the
bottom edge of the cover thread, approx. 3 liters)
Clean the filter(s) when changing the water or when the “water pressure too low
“message appears. Remove the filter(s) from tank and hold under warm water while
washing out material. Change the filter(s) immediately if damaged; otherwise every 3
months or after 3-4 filter cleanings. Clean the cooling water jets if they do not strike the
machining instruments by carefully removing any foreign particles from the water
nozzles with a cleaning wire or probe. This will help to extend the life of the instruments.
Changing the Filter Bag (CEREC Suction Device)
If there is a significant fall in suction power when dry milling zirconia, the filter bag (REF
65 78 095) could be full and will need replacing. Typically a filter bag should offer
capacity for ca. 120 restoration units. This number can vary depending on the amount of
zirconia material milled and extracted. To change the filter bag:
Loosen and remove the two knurled nuts on the maintenance cover.
Remove the cover.
Remove the full bag from the nozzle and replace with a new one.
Place the cover back on and screw tighten the two knurled nuts.
Note: ensure that the cap is sealed properly and the filter bag is not jammed.
Using the Cleaning Hose and Wet Cleaning Process
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The milling chambers of units used for dry milling zirconia should be regularly cleaned
to avoid a build-up of excess zirconia dust. A cleaning hose with nozzle can be used for
this. This hose is ordered separately as a spare part (REF 65 89 795).
2.2 Equipment maintenance
Another reason for lost production is delays caused by waiting for spare parts after
equipment breaks down. As a minimum, cereal processors should monitor the state of
equipment that is likely to wear out and as their experience grows over the years, they
should buy spare parts or send the machine for servicing when they expect that a
component is due to be replaced. There are likely to be a few parts that wear out more
quickly than others (e.g. mixer bearings, heating elements in bag sealers, drive belts
and hammers in mills). These should be identified and spare parts kept in stock.
Processors can make an agreement in advance, possibly involving a small annual fee,
to ensure that electricians or mechanics repair equipment as a priority. Lack of
maintenance is one of the most common problems that cause small-scale millers and
bakers to lose money. Machine breakdowns arise from a number of different causes.
They reduce productivity and increase production costs. Poorly maintained machines
also produce substandard products and can contaminate products with metal
fragments, as well as being a potential hazard to operators. Another common cause of
failure is when those who operate or maintain a machine arbitrarily alter it. Proper
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maintenance ensures that machinery operates correctly and safely and prolongs its life,
thus reducing capital and operating expenditure. To put preventive maintenance into
practice, the following actions are needed:
Identify priority machinery which has components that wear out more frequently.
Make a clear description of the procedures and standards for the work of
machine operators and maintenance workers (such as lubricating, tightening
bolts, adjustments etc.) in daily, weekly, monthly and yearly routine maintenance
plans as follows:
Before every wet machining process
o Ensure that the water and Dentatec solution completely covers
the filter(s) in the water tank
Weekly
o Change water in water tank and add 75ml Dentatec
Monthly
o Clean water filter monthly or as needed depending on usage
(change filter every 3-4 cleanings)
o Check and clean water jets to ensure that water is striking
the tools during wet machining
o Clean manual block clamp inside of the block axle
o Clean motor clamping cones for instruments without chuck
Yearly
o Annual maintenance carried out by a Service Technician
Dry milling zirconia only: Every 10 dry milled zirconia restorations
o Vacuum chamber and run wet cleaning program
Every 120 dry milled zirconia restorations
o Change filter bag (change HEPA filter every 3-4 filter bags)
Organize a schedule and train staff to implement maintenance plans.
Prepare a maintenance budget.
Record inspection results, analyze the records and evaluate the success of
maintenance.
Continuously update procedures and standards.
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NB: It is important to remove flour dust from equipment daily. A build-up of dust causes
rust to develop and on electrical equipment it causes moving parts to jam. It can also
seal the greasing points on machines and cause motors and engines to overheat and
burn out or seize.
2.3 Lighting, and power services
2.3.1 Lighting and power
Where lighting is needed, florescent tubes use less electricity than bulbs, but care is
needed when using fluorescent lights above mills, dehullers and other equipment that
has moving or rotating parts. This is because they can make machinery appear
stationary at certain speeds, causing a hazard to operators. Electricity is preferred for
bakery ovens because it is clean, flexible and easily controlled. Electric motors should
be fitted with isolators and starters. Plugs should be fitted with fuses that suit the power
rating of the equipment and the main supply should have an earth-leakage trip switch.
All electric wiring should be of the correct type for the intended purpose and installed by
a qualified and competent electrician. Where a three-phase (440 volt) supply is used in
larger mills, the load should be equally spread over the three phases. Multiple sockets
should not be used because they risk overloading a circuit and causing a fire. Cables
should be properly fixed to walls or run vertically from the ceiling to machines. There
should be no exposed wires at any connection.
2.3.2 Water supply and sanitation
Water is used in bakeries to make dough and for washing equipment. An adequate
supply of potable (safe for drinking) water should be available from taps in the
processing room. There are two potential problems with the water quality: sand and
contaminating microorganisms. Water from boreholes is likely to be relatively free from
micro-organisms, but may be contaminated with sand. River water is likely to be
contaminated with microorganisms and should only be used if no other source is
available. Samples of water should be periodically checked (e.g. once per year) for
microbial contamination at the Ethiopian laboratory, Department of Food Science and
Technology, Addis Ababa, or one of the commercial testing laboratories in Addis Ababa.
Because the amounts of water used in mills and bakeries are relatively small, any
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sediment can be removed by filtering. If micro-organisms are likely to contaminate the
water, they can be removed by water filters, by boiling water for 10-15 minutes, or by
dosing water with bleach (water for cleaning should be dosed by mixing 1 liter of bleach
into 250 liters’ of water. Water that is used as an ingredient has 2.5 ml of bleach to 250
liters of water). Care is needed when using bleach because it damages the skin and
particularly the eyes and can cause breathing difficulties if inhaled. It also corrodes
aluminium equipment.
Good sanitation is essential to prevent contamination of raw materials and processed
products by pests. Milling and bakery equipment should be thoroughly cleaned after
each day’s production, using a cleaning schedule that is clearly understood and
followed by production workers. Insects and rodents are attracted to food that is left
lying around and wastes should be removed each day and flour dust cleaned up.
Wastes should not be left in a processing room overnight. Hulls and bran should be
considered as by-products rather than wastes and sold to animal/poultry farmers or for
use in alternative products. Bulk stores of flour should be protected in a pest-proof
storeroom and small amounts of ingredients should be stored in insect- and rodent-
proof containers. Rodent traps are useful (but not poison) and if affordable, electric
‘insectocuters’ should also be used.
2.3.3 Fuels
Diesel is the preferred fuel for mills/dehullers etc., where electricity is not available. In
bakeries, fuel is one of the main costs if electric ovens are not used and the choice of
fuel is one off the main factors that determines the profitability of a business. Different
fuels have advantages and limitations in terms of cost, safety, risk of contamination of
products, flexibility of use and capital and operating costs of the oven. The cheapest
fuel is not always the most economical and it is necessary to carefully select the best
fuel to use in a bakery. Traditionally, wood has been cheap or free in Ethiopia and so
widely used in bakery ovens. However, deforestation in some areas has resulted in
increased cost of wood and legal restrictions on tree felling. It also produces a light fluffy
ash that can easily contaminate products. Charcoal is more expensive than wood, but it
produces a more intense heat with little smoke and a more compact ash. Bottled gas
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(LPG) is available in large urban centres and as fuel prices are constantly changing, this
may be cheap enough to compete with solid fuels. Other liquid fuels, such as kerosene
or diesel are not widely used because of the special burners required and the risk of
contaminating the product with off-odours. Petrol burners should not be used under any
circumstances because of the risk of an explosion.
2.3.4 Energy conservation
Bakeries and mills use large amounts of energy and their profitability depends partly on
reducing energy consumption. This can be done by only switching on mills, dehullers
etc. when they are needed, or by baking a sequence of different products as ovens
cool, to use all the available heat. Switching off lights in storerooms, or reducing vehicle
fuel consumption by coordinating product deliveries with collection of ingredients or raw
14 materials can make other savings. Other ideas include solar water heating (e.g. for
washing equipment), the use of fuel briquettes made from bran rather than fuel-wood
and using local suppliers of raw materials that can be delivered by bicycle, rather than
using a vehicle to collect them. When everyone does this, it can result in national
environmental and economic benefits by reducing deforestation and importation of
fuels.
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October 2019
Self-Check – 2 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Short Answer Questions
1. Write down why milling house require cleaning, maintenance and services
2. Indicate the clear description of the procedures and standards for the work of
machine operators and maintenance workers (such as lubricating, tightening bolts,
adjustments etc.) in daily, weekly, monthly and yearly routine maintenance plans
Note: Satisfactory rating - 5 points Unsatisfactory - below 5 points
You can ask you teacher for the copy of the correct answers.
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Information Sheet 3- Defining operation equipment and process
3.1 Introduction
For efficient production and high productivity, the capacity of each piece of equipment in
a process should match the others. This prevents money being wasted on equipment
that is larger than necessary, or creating ‘bottlenecks’ caused by one piece of
equipment that is too small. For example, the output of a seed cleaner should match
that of the dehullers and the maize mill. The equipment that is required in a small flour
mill is shown in Table 1.
3.2 Milling equipment operational process
Table1. Equipment for milling
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The main items are seed cleaner, dehullers, a mill and packaging equipment and
these are described in simplified milling process diagram below (Figure 1).
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Figure1. Simplified milling process diagram
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The design and construction of feed hoppers, dehullers, mills and other equipment
should allow free passage of grains or flour without any recesses that could trap food
and lead to contamination. Careful design and construction also prevent the release of
dust from equipment. Most milling equipment is made from mild steel and it is important
that welding is done to a high standard, without holes in the weld or small projections
that could trap food. All welds should be ground to a smooth finish. Mild steel easily
rusts and it is important that equipment is kept dry to prevent rust from contaminating
the grain or flour. A mill or dehullers should be easy to dismantle for cleaning and
maintenance. Nuts and bolts that are routinely removed should be made from high
quality steel so that threads do not wear out quickly. Worn bolts have the potential to fail
and damage a mill or dehullers and injure an operator and metal fragments contaminate
the flour. Wherever possible, it is better to buy equipment from local suppliers or
engineering workshops because it should be faster and easier to have machines
serviced or to obtain spare parts. If equipment must be imported, the following points
should be considered when ordering it:
Say exactly what is required (manufacturers may have a range of similar
machines).
Give the throughput required in kg or liters per hour and the type of food to be
processed.
Where possible, give other information (model number of machine, single or
three-phase power, number and types of spare parts required).
3.3 Safe Work Procedure Checklist
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Table 2. Milling machine pre-operation, operation and post-operation procedure
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Self-Check – 3 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Short Answer Questions
1. List down at least five equipment that is required in a small flour mill.
2. Draw the simplified flow diagram of mill by sequence and variation of operation.
You can ask you teacher for the copy of the correct answers.
Note: Satisfactory rating - 4 points Unsatisfactory - below 4 points
You can ask you teacher for the copy of the correct answers.
Page 28 of 137
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October 2019
Information sheet 4- Adjusting machine components and related attachments
4.1 Introduction
Grain mill machine is mainly consist of feed hopper, milling body, drive motor, frame
etc. The body and rotor assembly together form the crushing chamber, rotor assembly
roomis the main working parts, materials of shattered in the crushing chamber
complete. When the material entered into the crushing chamber, by the round and flat
part of the tooth gear fault strike and knead into effect, broken materials into a fine
powder quickly and plasma shape, then air flow in the centrifugal force function, grinded
materials through the sieve get into discharge hole discharge of corn milling machine.
The attachment is standard or special auxiliary devices intended to be fastened to or
joined with one or more components of the milling machine. These devices increase the
capability of milling machine. One machine can perform number of operation by using
various types of attachments. Moreover, an efficient and positive method of holding
workplaces to the milling machine table is important if the machine tool is to be used to
its fullest advantage. The most common methods of holding are clamping a workpiece
to the table, clamping a workpiece to the angle plate, clamping the workpiece in fixtures,
holding a workpiece between centers, holding the workpiece in a chuck, and holding the
workpiece in a vise.
4.2 Methods of mounting workpieces
4.2.1 Clamping Workpieces to the Table
When clamping a workpiece to the worktable of the milling machine, the table and
the workpiece should be free from dirt and burrs. Workpieces having smooth
machined surfaces may be camped directly to the table, provided the cutter does not
come in contact with the table surface during milling. When clamping workplaces
with unfinished surfaces in this way, the table face should be protected from damage
by using a shim under the workpiece. Paper, plywood, and sheet metal are shim
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materials. Clamps should be located on both sides of the workpiece if possible to
give a full bearing surface. These clamps are held by T-slotbolts inserted in the T-
slots of the table. Clamp supports must be the same height as the workpiece. Never
use clamp supports that are lower than the workpiece. Adjustable step blocks are
extremely useful to raise the clamps, as the height of the clamp bar may be adjusted
to ensure maximum clamping pressure. Clamping bolts should be placed as near to
the workpiece as possible so that the full advantage of the fulcrum principle may be
obtained. When it is necessary to place a clamp on an overhanging part, a support
should be provided between the overhang and the table to prevent springing or
possible breakage. A stop should be placed at the end of the workpiece where it will
receive the thrust of the cutter when heavy cuts are being taken.
4.2.2 Clamping a workpiece to the angle plate
Workpieces clamped to the angle plate may be machined with surfaces parallel,
perpendicular, or at an angle to a given surface. When using this method of holding
a workpiece, precautions should be taken similar to those mentioned for clamping
work directly to the table. Angle plates are either adjustable or nonadjustable and
are generally held in alignment by keys or tongues that fit into the table T-slots.
4.2.3 Clamping workpieces in fixtures
Fixtures are generally used in production work where a number of identical pieces
are to be machined. The design of the fixture depends upon the shape of the piece
and the operations to be performed. Fixtures are always constructed to secure
maximum clamping surfaces and are built to use a minimum number of clamps or
bolts in order to reduce the setup time required. Fixtures should always be provided
with keys to assure positive alignment with the table T-slots.
4.2.4 Holding workpieces between centers
The indexing fixture is used to support workpieces which are centered on both
ends. When the piece has been previously reamed or bored, it may be pressed upon
a mandrel and then mounted between the centers. Two types of mandrels may be
used for mounting workpieces between centers. The solid mandrel is satisfactory for
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many operations, while one having a shank tapered to fit into the index head spindle
is preferred in certain cases. A jackscrew is used to prevent springing of long
slender workpieces held between centers or workpieces that extend some distance
from the chuck. Workpieces mounted between centers are fixed to the index head
spindle by means of a lathe dog. The bent tail of the dog should be fastened
between the setscrews provided in the driving center clamp in such a manner as to
avoid backlash and prevent springing the mandrel. When milling certain types of
workpieces, a milling machine dog is held in a flexible ball joint which eliminates
shake or spring of the dog or the workpiece. The flexible ball joint allows the tail of
the dog to move in a radius along the axis of the workpiece, making it particularly
useful in the rapid milling of tapers.
4.2.5 Holding workpieces in a chuck
Before screwing the chuck to the index head spindle, it should be cleaned and any
burrs on the spindle or chuck removed. Burrs may be removed with a smooth-cut,
three cornered file or scraper, while cleaning should be accomplished with a piece of
spring steel wire bent and formed to fit the angle of the threads. The chuck should
not be tightened on the spindle so tightly that a wrench or bar is required to remove
it. Cylindrical workpieces held in the universal chuck may be checked for trueness by
using a test indicator mounted upon a base resting upon the milling machine table.
The indicator point should contact the circumference of small diameter workpieces,
or the circumference and exposed face of large diameter pieces. While checking, the
workpiece should be revolved by rotating the index head spindle.
4.2.6 Holding Workpieces in the Vise
As previously mentioned, five types of vises are manufactured in various sizes for
holding milling machine workpieces. These vises have locating keys or tongues on
the underside of their bases so they may be located correctly in relation to the T-
slots on the milling machine table (Figure 1).
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Figure 1. Locating key and vises
The plain vise similar to the machine table vise is fastened to the milling machine
table. Alignment with the milling machine table is provided by two slots at right
angles to each other on the underside of the vise. These slots are fitted with
removable keys that align the vise with the table T-slots either parallel to the
machine arbor or perpendicular to the arbor. The swivel vise can be rotated and
contains a scale graduated in degrees at its base which is fastened to the milling
machine table and located by means of keys placed in the Tslots. By loosening the
bolts which clamp the vise to its graduated base, the vise may be moved to hold the
workpiece at any angle in a horizontal plane. To set a swivel vise accurately with the
machine spindle, a test indicator should be clamped to the machine arbor and a
check made to determine the setting by moving either the transverse or the
longitudinal feeds, depending upon the position of the vise jaws. Any deviation as
shown by the test indicator should be corrected by swiveling the vise on its base.
The universal vise is used for work involving compound angles, either horizontally or
vertically. The base of the vise contains a scale graduated in degrees and can rotate
360° in the horizontal plane and 90° in the vertical plane. Due to the flexibility of this
vise, it is not adaptable for heavy milling. The all-steel vise is the strongest setup
where the workpiece is clamped close to the table. This vise can securely fasten
castings, forgings, and rough-surface workpieces. The jaws can be positioned in any
notch on the two bars to accommodate different shapes and sizes. The air or
hydraulically operated vise is used more often in production work. This type of vise
eliminates the tightening by striking the crank with a lead hammer or other soft face
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hammer. When rough or unfinished workpieces are to be vise mounted, a piece of
protecting material should be placed between the vise and the workpiece to
eliminate marring by the vise jaws. When it is necessary to position a workpiece
above the vise jaws, parallels of the same size and of the proper height should be
used. These parallels should only be high enough to allow the required cut, as
excessive raising reduces the holding ability of the jaws. When holding a workpiece
on parallels, a soft hammer should be used to tap the top surface of the piece after
the vise jaws have been tightened. This tapping should be continued until the
parallels cannot be moved by hand. After the workpiece is set, additional tightening
of the vise should not be attempted, as such tightening has a tendency to raise the
work off the parallels. Correct selection of parallels is illustrated in Figure 2.
Figure 2. Mounting in the Vise workpiece
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Whenever possible, the workpiece should be clamped in the center of the vise jaws.
However, when necessary to mill a short workpiece which must be held at the end of
the vise, a spacing block of the same thickness as the piece should be placed at the
opposite end of the jaws. This will avoid strain on the movable jaw and prevent the
piece from slipping. If the workpiece is so thin that it is impossible to let it extend over
the top of the vise, holds down straps are generally used (Figure 3). These straps are
hardened pieces of steel, having one vertical side tapered to form an angle of about 92°
with the bottom side and the other vertical side tapered to a narrow edge. By means of
these tapered surfaces, the workpiece is forced downward into the parallels, holding
them firmly and leaving the top of the workpiece fully exposed to the milling cutter.
Figure 3. Application of hold-down strap
4.2.7 Indexing
Indexing is the process of evenly dividing the circumference of a circular workpiece into
equally spaced divisions, such as in cutting gear teeth, cutting splines, milling grooves
in reamers and taps, and spacing holes on a circle. The index head of the indexing
fixture is used for this purpose.
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4.2.7.1 Index Head
The index head of the indexing fixture (4) contains an indexing mechanism which is
used to control the rotation of the index head spindle to space or divide a workpiece
accurately. A simple indexing mechanism consists of a 40-tooth worm wheel fastened to
the index head spindle, a single-cut worm, a crank for turning the wormshaft, and an
index plate and sector. Since there are 40 teeth in the worm wheel, one turn of the
index crank causes the worm, and consequently, the index head spindle to make 1/40
of a turn; so 40 turns of the index crank revolve the spindle one full turn.
Figure 4. Indexing fixture
4.2.7.2 Index Plate
The indexing plate (Figure 5) is a round plate with a series of six or more circles of
equally spaced holes; the index pin on the crank can be inserted in any hole in any
circle. With the interchangeable plates regularly furnished with most index heads, the
spacing necessary for most gears, bolt heads, milling cutters, splines, and so forth can
be obtained. The following sets of plates are standard equipment: Brown and Sharpe
type consists of 3 plates of 6 circles each drilled as follows:
Plate I - 15, 16, 17, 18, 19, 20 holes
Plate 2 - 21, 23, 27, 29, 31, 33 holes
Plate 3 - 37, 39, 41, 43, 47, 49 holes
Cincinnati type consists of one plate drilled on both sides with circles divided as follows:
First side - 24, 25, 28, 30, 34, 37, 38, 39, 41, 42, 43 holes
Second side - 46, 47, 49, 51, 53, 54, 57, 58, 59, 62, 66 holes
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Figure 5, Index plate and sector
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Self-Check – 4 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Short Answer Questions
1. Why an efficient and positive method of holding workplaces to the milling machine
table is important?
2. What is milling machine attachment, and why it is needed?
3. List down and explain at least three methods of mounting workpieces.
You can ask you teacher for the copy of the correct answers.
.
Note: Satisfactory rating - 5 points Unsatisfactory - below 5 points
You can ask you teacher for the copy of the correct answers.
Page 37 of 137
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Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Information sheet 5- Identification of processing and operating parameters
5.1 Introduction
This sheet is aimed at improving the effectiveness of cereal milling machines. It involves
steps like assessing of cereal products and cereal milling process, identification of the
cause of the problem, determination of factors recommendation. In this work, cereal
called rice taken in order to smooth the working activity.
5.2 Study of rice products and rice milling process
5.2.1 Rice products
The national bureau of agricultural commodity and foods standards, ministry of
agriculture and cooperatives, has divided rice seeds into three types according to milling
characteristics, namely, paddy husk, brown rice and white rice or milled rice. There are
four components to the structure of rice grains: husk, germ, rice bran, and endosperm.
The husk is the outermost layer which protects the exterior of the grain. It is made of
cellulose and hemicelluloses. Once the husk is removed, brown rice is obtained. The
brown rice is composed of rice germ (or embryo) and endosperm or white rice covered
by rice bran. Rice bran consists of layers of tissues covering the grain, and it is a rich
source of nutrient. The endosperm is the part of the grain that is consumed, primarily
consisting of carbohydrate in starch form.
For the sale of rice grains, whole kernels can be sold at a higher price than broken
grains. Whole kernels refer to intact rice grains containing no broken parts and including
at least 90 % of the grain length. Broken grains, on the other hand, mean broken rice
grains with lengths of at least 25% of the grain length. Broken grains also refer to split
rice grains with less than 80 percent of grain volume.
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Figure1. Cereal primary processing (in the milling machine)
Figure 2. Secondary processing of cereals (in the milling machine)
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Figure 3. Raw materials processing (store to medium milling machine)
5.2.2 Cleaning and grading operation
Cleaning process aims to protect the milling equipment, the quality of the milling
products and the consumer health. Foreign substance content and level of
contamination in the milled wheat batch are very important in achieving good quality in
flour. From this aspect, purchasing them based on the criteria and diligence is
paramount.
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Table 1. Cleaning and grading equipment
Equipment category Scale Name of the equipment
Cleaners S-M Seed Cleaners/Graders TA Range
M-L Seed Cleaners/Graders TAE Range
S-M Hand Operated Grain Cleaner
S-M Pedal-cum-Power Operated Grain Cleaner
S-M Rice Polishing Machine RS 40
S-M Rice whitener VSW 40
M-L Screen Air Separator
M-L Sab-Pre Cleaner and UB Fine Cleaner
Graders M-L Grain Cleaning Machine
M-L Grain Cleaner
M-L Grain - Seed - Flour Cleaner and Grader
M-L Mechanized Grader
Graders M-L Mechanized Grader
S-M Grain - Flour Separator
S-M Precision Air Classifier
M-L Gravity Separator
5.2.3 Quality control operation
Table2. Suppliers for testing and quality control
Equipment category Scale Name of Equipment
Temperature control S-M thermometer general purpose
Weight control S-M add and weigh scale
Volume control S-M mixer jugs
pH control S-M battery operated pH met
Brine control S-M Brine meter
Refractometers S-M Fisher brand Refractomete
Water treatment S-M Soda stream filter stream on line water filter unit
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5.3 Identification of the Cause of the Problem
After studying the components of the rice milling machine and parameters related to rice
milling, the causes of high rice breakage percentage were might found to be as follows:
Machine - Knob spacing adjustment, inadequate maintenance.
Method - Paddy rice flow rate, motor revolution speed.
People -Inadequate knowledge and skills on machine usage.
Raw Materials - Paddy rice moisture, rice strain, paddy rice storage.
5.4 Determination of Factors
Let us say, based on examination of each cause, three factors were found to likely
impact the breakage percentage of rice, namely, size of hopper feed, gap adjuster, and
outlet regulator. This research used the 3x3 full factorial experiment designs to search
for factors that significantly impact the rice breakage percentage. Each factor was
divided into three levels as shown in the Table1
Table 1. Factor levels
Factor Low Medium High
Input hopper rice (cm2 ) 4 8 12
White Rice Adjuster (cm) 3 4 5
Gap Rice Adjuster (mm) 4 5 6
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Self-Check – 5 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Short Answer Questions
1. List down operations that can be performed in a milling machine.
2. Compare and contrast plain milling operation with the rest milling machine.
You can ask you teacher for the copy of the correct answers.
Note: Satisfactory rating - 5 points Unsatisfactory - below 5 points
You can ask you teacher for the copy of the correct answers.
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Information sheet 6- Checking and adjusting equipment performance
6.1 Introduction
Reviewing workflow to adjust and keep equipment working properly can improve
productivity in the grain milling industry. Some of these maintenance tasks can be
performed by machine shop staff, while other tasks can be performed by the machine
owner. Below, we’ll look at just a few things you need to keep in mind to properly
maintain milling machines.
6.2 Lubrication
One way to keep tools for machine services in good condition is by making sure that
they are adequately lubricated. In order for machines to work properly, they must have
the proper lubrication that allows all parts to move smoothly. But before you start
lubricating your milling machine every five minutes, make sure you’re 100% aware of
how often you should be lubricating and how much lubricant you need to be using.
Precision is key when maintaining machine tools!
6.3 Cleaning
Another requirement for keeping a piece of machinery usable is making sure that is
properly cleaned after use. Many machine parts are often exposed to dirt and other
contamination, so it’s crucial to keep your machine clean to prevent any problems. If
you’re having any issues with operating your milling machine, dirt could be the culprit! If
you’re unsure where to look or you think your machine could use a professional
cleaning, take your machine to a machine shop. There, machine shop employees will
be able to provide a thorough cleaning and help prevent any problems from occurring in
the future. In addition, they can provide machine tool repair services if you find that
some part of your machine needs repair or replacement. Rebuilding tools certainly isn’t
an expense you should be paying often, so it’s a good idea to try and fix a small issue
before it takes a toll on your machines.
6.4 Daily Inspections
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By keeping up with daily inspections, you can prevent a problem from happening right
from the get-go. This is especially important if you’re using your milling machine on a
daily basis. If something is amiss and you start using your machine without thoroughly
inspecting it first, you may be in for a world of trouble. If something looks fine one day
and operates wrong the next, an inspection can catch the issue before it’s too late.
If you find any problem with your tool but are unsure of how to fix it, reach out to your
machine shop immediately for the fix or other tips. But until then, make sure you’re
practicing good maintenance with all of your machine tools.
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Self-Check – 6 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Short Answer Questions
1. What are the few things you need to keep in mind to properly maintain milling
machines?
2. Why daily machine inspection is important?
You can ask you teacher for the copy of the correct answers.
Note: Satisfactory rating - 5 points Unsatisfactory - below 5 points
You can ask you teacher for the copy of the correct answers.
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October 2019
Information Sheet 7- Carrying out pre-start checks
7.1 Introduction
A visual “circle check” or pre-operational inspection of equipment prior to every use will
reduce the chance of equipment being operated in an unsafe condition. This makes it
easier to spot and deal with maintenance issues early before they turn into a problem
causing downtime, equipment damage or expensive repairs. Unsafe machinery can
also cause injury to the operator or other workers and damage to facilities or product.
7.2 Background
The Operator’s manual and maintenance records for each piece of equipment are
readily available to check on the need for operation procedure (oil and filter changes,
greasing, seal replacement and so on). Ensure maintenance records are checked
regularly and performed as scheduled or needed. Manuals and maintenance records for
our equipment are kept.
7.3 Caution
A pre-operational inspection of equipment is not the same as training to operate the
equipment. Do not operate or work with equipment unless you have been properly
trained to do so.
7.4 Safety rules & basics for milling machines
Milling machines are used to grind grains in the circular plate. The rotating bit is
extremely sharp and requires special safety precautions while being used. Be sure to
always follow good safety practices in the shop as described in general robotics safety
Rules. Specific safety requirements for milling machines are:
Do not make contact with the revolving cutter. Keep fingers at least 6” away.
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Even a non-revolving cutter is dangerously sharp- watch where you place your
hands
Remove spindle wrench immediately after securing bit in collet.
Place a wooden pad or suitable cover over the table surface to protect it from
possible damage…or just never place wrenches, hammers or other metal tools
on the mill table.
Use the buddy system when moving heavy attachments.
Do not attempt to tighten arbor nuts using machine power.
When installing or removing milling cutters, always hold them with a rag to
prevent cutting your hands.
While setting up work, install the cutter last to avoid being cut.
Never adjust the workpiece or work mounting devices when the machine is
operating.
Check and set the proper speed, feed, and depth of cut before cutting into the
metal
Chips should be removed from the workpiece with an appropriate rake and a
brush
Do not blow chips around or clean the machine slides with an air hose. Use
brushes and shop vac.
Shut the machine off before making any adjustments or measurements.
When using cutting oil, prevent splashing by using appropriate splash guards.
Cutting oil on the floor can cause a slippery condition that could result in operator
injury
When loosening a collet, tap the top of the draw bar with a soft face mallet
ONLY-no steel! (UNM-LA)
When engaging power table feed (UNM-LA), make sure no one is standing by
the table handles
Know how to indicate-in a vise and tram-in a head to make sure everything is
square
Some form of coolant or cutting fluid should be used when cutting metal
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Use parallels to position work in the vise, and be careful that the cutter doesn’t
make contact with the vise or table.
Keep vise jaws clean so that parts and jaws do not become “dented.”
Self-Check – 7 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Short Answer Questions
1 Why milling machine carrying out pre-start checking is needed?.
2 What are these pre-start check lists?
3 What are the main purposes of grinding machines?
You can ask you teacher for the copy of the correct answers.
Note: Satisfactory rating - 5 points Unsatisfactory - below 5 points
You can ask you teacher for the copy of the correct answers.
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Operation Sheet 1- Guidelines for correct grain storage
The following sequence is provided as a step-by-step example of a typical Guideline
for correct grain storage.
In order to attain correct and sustainable grain storage, Follow this guidelines.
Guidelines for correct grain storage
Make sure the storeroom is waterproof by locating it on well drained land, raising
it above the ground and fitting a waterproof roof
Prevent the temperature in the store from fluctuating by using insulating
materials (brick, mud, clay, wood or other insulation), painting the outside white
and fitting an overhanging roof to keep sunlight off the walls.
Ensure that the store is insect-proof, rat-proof and bird-proof
Thoroughly clean storerooms by removing and burning all old grain, straw,
insects etc. to prevent contamination of new grain
Make sure that grain is properly dried before putting it into a store
If chemical insecticides or fungicides are used, ensure that manufacturer’s
recommended dosages are followed.
Regularly check the grain for infestation, signs of mould or discolouration and
ensure that it is not getting hot (each is a sign of excessive moisture). If these
are found, remove the grain and re-dry it.
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Operation Sheet 2- Cleaning steps for excess zirconia dust avoidance
The milling chambers of units used for dry milling zirconia should be regularly cleaned
to avoid a build-up of excess. When dry milling zirconia recommended to use wet
cleaning process or wet grind, a restoration is essential at least once a week or after
every ten dry-milled restorations.
Steps of using cleaning hose and wet cleaning process
Remove the milling unit hose from the top of the suction device.
Connect the cleaning hose to the top opening of the suction device.
Activate the suction device’s manual function by changing the switch setting on
top of the device from “Auto” to “On”.
Vacuum excess dust from the chamber as needed.
Remove excess dust from the block shaft and the underside of the baffle
plate located on the block axis. (See both arrows in picture 4)
After the chamber has been vacuumed the wet cleaning process in the
software should be used 2-3 times as needed to remove excess dust.
In the software’s system menu, navigate to “Configuration“, then click on
the “Devices “button.
Select the applicable unit.
Click on the option “Service “then “Start a cleaning process“.
Notes: A restoration can be wet grinded to achieve a similar cleaning effect. A nylon
brush can also be used to remove zirconia dust from around the base of the block shaft
in between wet cleaning processes.
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Operation Sheet 3- Milling machine safe work procedure
The following Milling machine safe work procedure is provided, then it is must to wear
step-by-step following workplace health and safety regulations.
Milling machine safe work procedure
Properly use all personal protective equipment required.
Wear eye protection.
Wear appropriate footwear.
Appropriate attire.
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Operation Sheet 4– Procedures of mounting feed grinding machine
If cylindrical grinding is to be performed, such as grinding of workplaces mounted in the
grinding may be done with the work piece set up between centers, held in a chuck and
supported by a center rest, or clamped to a faceplate as in lathe setups. Use the
following methods when mounting the work piece between centers:
Use a dead center in the tailstock spindle. This method is preferred because it
eliminates any error caused by wear in the machine’s spindle bearings. Before
grinding check the accuracy and alignment of centers and correct if necessary.
To grind the centers, follow the procedures for grinding lathe centers
After the centers are accurate, align the centers by one of the methods prescribed
for aligning lathe centers.
Position the work piece between the centers, and use a lathe dog to revolve the
work piece.
Use the following methods and procedures when mounting the work piece for
conical grinding:
Work pieces for conical grinding can be set up in a chuck or between centers.
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The table is swiveled to the required taper by means of the graduations on the end
of the table (Figure 34.)
Since the table on a universal grinder is limited as to the degree that it can be
swiveled, steep conical tapers are normally ground by swiveling the headstock to the
angle of the taper desired (Figure 34).
Remember when a work piece is to be conically ground, the work piece axis and the
grinding wheel axis must be at the same height. Otherwise, the work piece will not
be ground at the correct angle.
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Draw and label correct selection of parallels which mounting in the Vise workpiece.
Figure. Mounting in the Vise workpiece
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Operation Sheet 5 – Rice milling process
Rice Milling Process
This is the initial stage of converting paddy rice into milled rice or brown rice that is
suitable for consumption. The grains have to be removed of excess humidity, to have a
humidity of 13-15 percent. The stages of rice milling process are as follows:
Paddy rice has to be cleaned to remove contaminants such as hay, vegetation,
dust, powder, gravel and sand from the paddy rice.
De-hulling is conducted to remove rice husks from the grains. In this stage, a
huller consisting of two rubber balls rotating into each other at different speeds or
a huller constructed of two steel panels padded with coarse stone is used to
create friction and remove the husks from the grain. The rice obtained from this
stage is brown rice, which still contains the fiber coating and embryo.
Whitening and polishing is the stage at which the rice bran is polished from the
brown rice, leaving only the endosperm. Rice bran is a byproduct of this stage.
In sorting the sizes of rice grains, sieves with openings for different sizes are
used to sort head rice from broken grains and rice ends.
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Operation Sheet 7 – Pre-operation of milling machine handling techniques
Do not operate or work with equipment unless you have been properly trained to do so.
Milling machine handling techniques
Task (Drawings, instructions, Specifications, Material… etc.) is clearly
understood.
Identify ON/OFF switch and emergency stop button and test any interlocking
devices (if applicable).
Make sure the machine is turned off or the emergency stop switch is
engaged, before comment of any work or inspection.
Ensure all security guards including the spindle guard are in place.
Ensure the work piece has been suitably prepared for the milling operation.
Ensure work piece is securely fastened to the working table.
Remove the chuck wrench/key immediately after installing the tooling.
Adjust speed and feed to suit the tooling diameter, material and turning
operation.
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Ensure the cutting tools are sharp, in good condition and secured.
Test the cooling fluid system operation and availability, if applicable.
Faulty equipment must not be used and must be immediately reported to the
shop technician
LAP Test Demonstration
Name----------------------------------- ID------------------------ Date--------------------------------
Time started: ________________________ Time finished: ________________
Instructions: Given necessary templates, tools and materials you are required to
perform the following tasks within 1 hour. The project is expecting you
to do it.
During your work: You can ask all the necessary tools and equipment
Lap Test Title: Produce Tool Shanks for Milling Machines
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Task Objectives / Demands: in accomplishing activities required for this project the
student will be able to: (During your work follow these steps)
LAP
Test
Demonstration
1 Show the guidelines for correct grain storage.
2 Practically show the steps help to use the cleaning hose and wet cleaning
process.
3 Perform milling machine safe work procedure
4 a. Draw and label correct selection of parallels which mounting in the Vise
workpiece
b. Perform the procedures of mounting feed grinding machine.
5 Apply or practically show the rice milling process.
6 . Perform pre-operation milling machine handling techniques
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Instruction sheet
This learning guide is developed to provide you the necessary information regarding the
following content coverage and topics:
Workplace information, policies and procedures.
Starting and operating the process
Monitoring equipment variation in operating conditions.
Identifying Variation in equipment operation.
Reporting maintenance as per workplace reporting format.
Monitoring and confirming process specification.
Removing fine bran from semolina and bran product.
Retuning fine bran product to purification or scratch rolls.
Identifying, rectifying and reporting out-of-specification product/process
outcomes.
Maintaining the work area with housekeeping standards
Conducting work with environmental standards and legislative requirements.
Maintaining workplace records
This guide will also assist you to attain the learning outcomes stated in the cover page.
Specifically, upon completion of this learning guide, you will be able to:
Follow workplace information, policies and procedures.
Start and operate the process
Monitor equipment variation in operating conditions.
Identify variation in equipment operation.
Report maintenance as per workplace reporting format.
Monitor and confirm process specification.
Removing fine bran from semolina and bran product.
LG #25 LO #2-Operate and monitor the milling and purification
process
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Return fine bran product to purification or scratch rolls.
Identify, rectify and report out-of-specification product/process outcomes.
Maintain the work area with housekeeping standards
Conduct work with environmental standards and legislative requirements.
Maintain workplace records
Learning Instructions:
1. Read the specific objectives of this Learning Guide.
2. Follow the instructions described below.
3. Read the information written in the information Sheets
4. Accomplish the Self-checks
5. Perform Operation Sheets
6. Do the “LAP test”
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Information Sheet 1- Workplace information, policies and procedures
1.1 Introduction
The workplace is the location at which an employee provides work for an employer.
That seems like a simple enough explanation, but it can become a bit more complex,
especially in today's knowledge economy.
.
1.2 Workplace information
Hand in hand with good manufacturing, hygiene and management practices, all
partners in the food supply chain must remain aware of the expanding number of
domestic and international food safety laws and regulations. Several incidences of food
contamination have led the Codex Alimentarius Commission to develop additional food
safety standards to enhance consumer health protection. These food safety laws,
regulations and standards are mandatory. To access markets, food commercial
enterprises must meet them through the application of good manufacturing/hygienic
practices (GM/HP) and hazard analysis critical control point (HACCP). The
implementation of sound quality assurance programmes is also a must to increase their
competitiveness.
1.3 Food safety laws
Millers and bakers should check the local laws with the Ethiopia National Bureau of
standards. In summary the registration of a mill or bakery involves the following:
Registration of the enterprise with the ministry of trade and industry
Obtaining a certificate of share capital (for limited companies), or a certificate
of incorporation for corporate companies.
Obtaining an occupational certificate from local authority, or the planning
authority in the land ministry
Obtaining a health permit or licence from the local authority or ministry of
health to allow the premises to be used for food production
Obtaining a manufacturing licence, issued by the local authority or ministry of
health
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Obtaining medical certificates from the health authority to certify that workers
are fit to handle food
Registration with the revenue office or tax office
1.4 Food regulations and standards
In Ethiopia there are both general regulations that apply to all foods and also
standards that are specific to particular types of food. Ethiopian National Bureau of
Standards should be consulted on details of the general regulations concerning:
Labelling
Presentation and advertisements
Weights and measures and
Hygiene practices during processing and handling
1.5 Food fortification regulations and standards
Millers and bakers should contact the ministry of health or the ministry of agriculture,
animal industries and fisheries for details of laws relating to public health, food safety
and hygiene and sanitation in their premises. Please note that parliament is considering
passage of a food safety bill or law that will complement the food safety strategic plan
and have broad-ranging impacts on all participations in the food chain. Small-scale
operators must remain in contact with the relevant enforcement agencies to remain in
compliance with the food safety bill or law.
1.5.1 Flours
Laws specify the maximum residue limits for pesticides etc. in grains and millers should
contact Ethiopian National Bureau of Standards for details. The moisture content of flour
cannot exceed 15% and the grade is specified by the allowable percentage of bran.
1.5.2 Labelling
Packaged flour should be labelled with the name and address of the miller and the
name of the flour (not the brand name but the type of flour (e.g. ‘maize flour’)). Flours do
not require date marking (e.g. ‘Best before’ or ‘Sell by’) if they are expected to have a
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shelf life of more than 12 months. Weaning foods made from cereal-legume mixtures
should conform to specifications of the Protein-Calorie Advisory Group of the United
Nations. As a minimum, the label on weaning food containers should have a clear set
of preparation instructions in the 100 languages spoken by customers and diagrams to
illustrate the preparation procedures, how often to feed the product and how much to
give the child. Label instructions should be fully tested among consumers of all
education levels and cultural backgrounds to ensure that they are properly understood.
1.6 Policy statement of intent
The health and safety policy statement of intent is often referred to as the health and
safety policy statement or simply (and incorrectly) as the health and safety policy. It
should contain the aims (which are not measurable) and objectives (which are
measurable) of the organization or company. Aims will probably remain unchanged
during policy revisions whereas objectives will be reviewed and modified or changed
each year. The statement should be written in clear and simple language so that it is
easily understandable. It should also be fairly brief and broken down into a series of
smaller statements or bullet points. The statement should be signed and dated by the
most senior person in the organization. This will demonstrate management commitment
to health and safety and give authority to the policy. It will indicate where ultimate
responsibility lies and the frequency with which the policy statement is reviewed.
1.7 Rules and procedures in grain milling operation
Any unsafe practice in grinding can be hazardous for operation and deserves careful
attention. Various important aspects in this respect are:
Grain mill selection: The milling machine for any grain milling operation should
be carefully chosen and the workpiece set up properly in the milling machine.
Milling machine inspection. Before mounting the wheel, it should be checked
for damage in transit, cracks and other defects. Ringing test is good enough
for vitrified bond wheels. Sound wheels, when tapped lightly at 45 from the
vertical line with a plastic hammer (non-metallic object) and listen for a brief
ring sound like a clear metallic ring. If there is a ring, the wheel is most likely
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oK, if it sounds dull/dead, do not use the wheel because the cracked wheel
will not ring.
Mill storage. When not used, the wheels should be stored in a dry room and
placed on their edges in racks.
Mounting of milling machine: The machine should be correctly mounted in the
spindle and enclosed by a guard. Wheel bore should not be a tight fit on the
sleeve.
Machine guards: These should always be used during milling, and
periodically adjusted to compensate for machine wear. Always fit wheel guard
securely in position closely over grinding wheel before starting machine, and
rotate spindle by hand before running on power to ensure wheels are free to
rotate and are not rubbing guards, fingers or fixtures.
Dust collection and health precaution: When grinding dry, provision for
extracting grinding dust should be made. Protective covers of machine should
never be removed while machine is in use. Operator should wear safety
devices to protect his eyes and body from flying abrasive particles and dust.
Wheel operation: Adequate power is essential in grinding machines. If power
is not adequate then wheels will slow down and develop flat spots, making
the wheel to run out-of-balance.
1.8 Setting up the machine
Inspect the mechanism to make sure nothing, aside from your stock, will
touch it, bind, or get caught on the equipment.
Keep the tool rest as close to the wheel but not touching it (gap should be
between 1/8” and 1/4”).
If the tool rest needs to be adjusted, unplug the machine first, and then adjust
it.
Where possible, always have the wheel rotation such that the grinding
pressure is into the support finger.
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Choose a finger most suited for the job. There is no definite shape to use, but
its length should be such that it gives adequate support to the work but is still
free to flex to allow it to trip from one work to another.
Fold back long sleeves up to the elbow.
No rings, wrist watches, bracelets, or other jewelry that could get caught in
the equipment.
1.8.2 Equipment using time
Make sure someone else knows that you are using the machine; press is
available in case of an emergency.
Be alert and cautious when using the grinding wheel.
Keep hands and arms well clear of rotating wheel (if you have long hair, make
sure it is tied back and will not touch the rotating wheel).
Gently feed the stock into the wheel, do not force it. Move it side-to-side to
avoid a hot spot on the wheel
Maintain good balance (stand erect with both feet straight and slightly apart)
while grinding your stock. Avoid leaning into the machine or stooping over the
wheel.
Clean up the shaving debris by using a brush or the shop vacuum to avoid potential
splinters from the shavings only after the equipment has been turned off, and the wheel
has stopped turning.
1.9 Repairs are necessary
If odd noise, excessive vibration, or if an unsafe condition is observed:
Turn machine off.
Unplug machine and install “Plug Lockout” device (give key to the teacher or
respective person) and install the “Tag out” label.
Do not repair it yourself.
Notify to your teacher, giving a description of what happened and your contact
information.
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1.10 Accident procedures
Administer proper First Aid; a kit is available in the specified work shop or room.
Call or if using Cell Phone for emergency assistance.
Seek medical help from Employee Health Services, or Student Health, or
Hospital (no need to phone them before going).
1.11 Workplace information systems template
Record the information to be stored or retrieved in the first column. Record the system
used to store/retrieve the information in the second column. Record your comment on
how effective you think the system is and what can be done to improve it in the last
column. An example has been provided.
Information/
information
type
System used to store and
retrieve information
Evaluation/suggested changes.
Photographs Currently photographs are stored
as hard copies in manila folders
that are filed in a cabinet.
Photographs are sorted in
categories and filed
alphabetically.
It is difficult to find the photos we
need with the method currently
being used. Many of them are
being damaged by being stored
in this way. It would be best to
store them electronically so they
can be shared more widely. We
could also then file images under
more than one category etc.
You could also comment on the
best software package to use or
record any other comments that
might be of value to management
in your organization.
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Self-Check – 1 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Short Answer Questions
1. Define what workplace is.
2. Among Step-by-step procedure for grinding the bore of a bushing, list down at least
four of them.
You can ask you teacher for the copy of the correct answers.
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
You can ask you teacher for the copy of the correct answers.
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Information Sheet 2- Starting and operating the process
2.1 Introduction
This sheet might discus on starting (Pre-operational safety checks) and operating the
feed Mill process.
2.2 protective devices
Compulsory protective devices are:
2.3 Pre-operational safety checks
Prior to commencing operation of the milling plant operators must familiarize
themselves with all aspects of the mill and auger system to the operating
instruction contained in the mill manual.
Ensure area around Phase Converters is clear of any obstruction and electric
motors have good air flow around cooling fins. Switch on each Phase
Converter one at a time and check that both have powered up properly.
Check all nuts, bolts and attachments to ensure that they have not shaken
loose during operation.
Ensure that all covers and safety guards are fitted and operation signs
attached to plant.
Locate all emergency stop buttons and note their location.
Locate and identify all electric motor isolating switches.
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Check all electrical leads. Do not operate if electrical leads are damaged.
On the Main Switch Board, Inspect and identify all control switches and the
power for their operation.
If in doubt ask.
Ensure work site is clear of tools and other equipment or debris to prevent
tripping.
Ensure that there is sufficient ventilation for fumes and dust to dissipate to
enable safe operation.
2.4 Operational safety checks
Select silo for which grain is to be used.
Open the silo slide gate approximately 2 cm by moving the slide handle which
is located on the outer ring of the silo base. Note: If the slide gate is open
wider than 2 cm then additional vertical load is placed on the auger screw, but
no additional feed of grain will occur, so there is no advantage to do so. Once
grain is flowing, slide can be set to appropriate position to maintain required
flow.
Check that the bunk which is to have the rolled grain is clean and clear of
other plant.
Once the selected bunk is determined, position the lever below the mill
discharge auger in the correct position.
Shut off slide gate to allow all grain through mill system and then shut down.
To start electrical power: Follow switch order for mill start.
To start the mill: Check the restart button before starting the mill. Use the
control points at surge bin and drag auger to regulate output.
Mill Adjustment - the mill adjustment screw requires manual setting by
loosening the lock nut and adjusting the mill settings (with large spanner).
Lock nut to be fastened again when required setting is made.
In the case of a blackout the mill will need to be restarted. Do not restart the
mill under load. Use caution when restarting the mill.
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Once milling is completed the system will need to be shut down. Close the
silo slide first to clear the drag, the surge bin and roller mill in sequence.
Lockout for any work on the mill is achieved by the isolator switch located on
the control panel.
2.5 Production Process
The production of flour consists of the following three processing parts.
Wheat cleaning and moistening
Wheat milling
Wheat flour after treatment
2.5.1 Cleaning equipment and working principle
Cleaning equipment is mainly the use of wheat and impurities in the size,
weight, shape, gravity, magnetic and other differences to clean up. These
devices include the following categories:
Screening equipment: such as roller screen, vibrating screen, plane rotary
screen
Scourer Equipment: such as wheat scourer, wheat brush machine, impact
machine.
DeStone equipment: such as destoner, the specific gravity grading
machine
Selection equipment:Such as disk cylinder separator
Winnowing device: vertical suction duct, circulating air separator.
Magnetic separation equipment: permanent magnetic cylinder
2.6.1 Grain cleaning process flow
Pre-cleaning process
Raw wheat cleaning process
Net wheat cleaning process
2.6.2 Cleaning requirements
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Impurities no more than 0.3%;
Grain impurities not more than 0.5%;
Sandstone no more than 0.015%;
Nonmagnetic metal;
Note: Both Figures are simplified flour mill plant
2.6 Wheat milling
Wheat flour is wheat bran and endosperm and the embryo and endosperm separation,
then grinding into powder process. The wheat grain is composed of three parts of
endosperm, embryo and oatmeal. Each part by weight percentage: 82 -85%
endosperm, embryos of 2 ~ 3%, 12 ~ 14% oatmeal. Endosperm contains a large
number of starches, and contains some of the gluten protein composition; it is the main
raw material to make pasta products. Oatmeal containing more fiber, less nutrition,
mainly used as feed. For wheat and wheat germ mixed with wheat flour will affect the
color and baking, and easy to deteriorate during storage, the separation of two and the
endosperm, is a necessary step in wheat flour.
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Self-Check – 2 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Short Answer Questions
1. Write down some cereal milling machine pre-operational safety cheeks.
2. What is wheat flour?
You can ask you teacher for the copy of the correct answers.
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
You can ask you teacher for the copy of the correct answers.
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Information Sheet -3 Monitoring equipment variation in operating conditions
3.1 Milling process
Succession of 3 systems
breaking
o breaks up grain in large pieces
o removing endosperm from bran
o as little flour and bran powder as possible
coarse reduction (scratching or sizing)
o removing small pieces of bran and embryo from endosperm
o smaller particles endosperm
fine reduction
o grinding endosperm into flour
o minimum in crushed germ and bran powder
o optimum in damaged starch granules
3.2 Roller milling
Fig 1. Milling
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3.3 Roller milling: break system
4-5 breaks, corrugated rolls
first break opens kernel
subsequent breaks: scraping endosperm from the bran
gradually smaller but more corrugations
differential from 2.5 to 1
3.4 Roller milling: reduction system
Gradual decrease of particle size into flour
Roller mill with smooth rolls,
differential 1.25 to 1
high shear pressure, lower shear forces
Coarse reduction: 3-5 stages
removing small pieces of bran and embryo from endosperm
smaller particles endosperm
no severe grinding: no bran in flour
Fine reduction: 6-10 stages
grinding endosperm into flour
minimum in crushed germ and bran powder
optimum in damaged starch granules
3.5 Hammer mill
impact milling
screen determines the particle size
requires dehulling when applied for ‘white’ flour/meal
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Figure 1 & 2. Hammer mill and sieve respectively.
3.6 Sieving: plansifter
Sieving stage follows each set of rolls
different mill fractions
directed to:
o Next break rolls
o Reduction rolls
o Purifier
o Finished product
3.7 Sieving
Purifiers
separation of pure endosperm and endosperm with different amounts of
bran
vibrating motion of sieves: heavier endosperm close to sieve, brannier
material on top
air currents fluidise and stratify according to size, specific gravity and
shape
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3.8 Milling and flour/meal quality
Particle size
Bran content -> ash content
Color
Starch damage
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Self-Check – 3 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Short Answer Questions
1. Milling process has systems successions. What are they?
2. List down on what the milling and flour/meal quality depend?
You can ask you teacher for the copy of the correct answers.
Answer Sheet
Score = ___________
Rating: ____________
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
You can ask you teacher for the copy of the correct answers.
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Information Sheet 4 - Identifying variation in equipment operation
4.1 Introduction
Milling is the process of machining flat, curved, or Milling machines are basically
classified as vertical or irregular surfaces by feeding the workpiece against a rotating
horizontal. These machines are also classified as knee-type, cutter containing a number
of cutting edges. The milling rams type, manufacturing or bed type, and planer-type.
Most machine consists basically of a motor driven spindle, which milling machines have
self-contained electric drive motors, mounts and revolves the milling cutter, and a
reciprocating coolant systems, variable spindle speeds, and power-operated adjustable
worktable, which mounts and feeds the workpiece table feeds
4.2 Milling machine parts
A milling machine consists of the following parts: Base, Column, Knee, Saddle, Table,
Overhanging Arm, Spindle, Arbor, Arbor Supports, Milling Head, and Ram
4.2.1 Base
It is the foundation part of a machine and all other parts are joined on it. It carries the
entire load so it should have high compressive strength and it is made up of cast iron.
4.2.2 Column
It is mounted vertically on the base. It supports the knee, table, etc. and work as
housing for the other entire driving member. The column is a hollow member which
contains driving gears and sometimes motor for the spindle and the table.
4.2.3 Knee
It is a casting that supports the saddle and table. All gearing mechanism is enclosed
within the knee. It is fastened to the column by dovetail ways. The knee is supported
and adjusted by a vertical positioning screw (elevating screw). The elevating screw is
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used to adjust the knee up and down by raising or lowering the lever either with the help
of hand or power feed.
4.2.4 Saddle
This is placed between the table and the knee, and work as an intermediate part
between them. This can moves transversally to the column face. This slides over the
guide ways provided situated on the knee which is perpendicular to the column face.
The main function is to provide motion in a horizontal direction to the workpiece.
4.2.5 Sable
This is a rectangular casting which is present on the top of the saddle. The table is
situated over the knee. It is the part of a machine that holds the workpiece while
machining. This is made by cast iron and has T-slot cut over it. This provides vertical
motion by moving the knee up and down. It provides horizontal motion by the feed
screw. This provides a horizontal (transverse) motion by moving the saddle.
4.2.6 Overhanging arm
The overarm is used to fastened arbor support. It may consist of one or two cylindrical
bars that slide through the holes in the column. It is made by cast iron.
Spindle: The spindle is the main part of the machine which holds the tool in the right
place. This spindle provides the drive for arbors, cutters, and attachments used on a
machine.
4.2.7 Arbor
This is a mechanical part, which is used as an extension part of the spindle in a
horizontal mill machine. It is fitted on the spindle whenever it's required. This holds the
tool and moves it in the correct direction.
4.2.8 Arbor Supports
There are generally two types of arbor supports used in the mill machine. The first one
has a small diameter bearing hole, 1-inch in maximum diameter, and the other one has
a large diameter bearing hole, usually up to 23/4 inches. The arbor support has an oil
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reservoir that lubricates the bearing surfaces. It can be clamped anywhere on the
overarm. The arbor support is used only in the horizontal types of milling machines.
4.2.9 Milling head
It is the upper section of a vertical mill machine. It consists of a spindle, driving motor
and other controlling mechanisms.
4.2.10 Ram
One end of the arm is attached to the column and other ends to the milling head. The
ram can be moved transversally ( in and out) on the column by a hand lever.
Milling is the process of machining flat, curved, or Milling machines are basically
classified as vertical or irregular surfaces by feeding the workpiece against a rotating
horizontal
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Self-Check – 4 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test: Short Answer Questions
1. Define what milling is. (3 points)
2. List down almost the all feed milling machine parts. (7 points)
Information Sheet 5 - Reporting maintenance as per workplace reporting format
5.1 Equipment maintenance
Another reason for lost production is delays caused by waiting for spare parts after
equipment breaks down. As a minimum, cereal processors should monitor the state of
equipment that is likely to wear out and as their experience grows over the years, they
should buy spare parts or send the machine for servicing when they expect that a
component is due to be replaced. There are likely to be a few parts that wear out more
quickly than others (e.g. mixer bearings, heating elements in bag sealers, drive belts
and hammers in mills). Processors can make an agreement in advance, possibly
involving a small annual fee, to ensure that electricians or mechanics repair equipment
as a priority. Lack of maintenance is one of the most common problems that cause
small-scale millers and bakers to lose money. Machine breakdowns arise from a
number of different causes. They reduce productivity and increase production costs.
Poorly maintained machines also produce substandard products and can contaminate
products with metal fragments, as well as being a potential hazard to operators. Another
common cause of failure is when those who operate or maintain a machine arbitrarily
alter it. Proper maintenance ensures that machinery operates correctly and safely and
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
You can ask you teacher for the copy of the correct answers.
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prolongs its life, thus reducing capital and operating expenditure. To put preventive
maintenance into practice, the following actions are needed:
Identify priority machinery which have components that wear out more frequently
Make a clear description of the procedures and standards for the work of
machine operators and maintenance workers (such as lubricating, tightening
bolts, adjustments etc.) In daily, weekly and monthly routine maintenance plans
Organise a schedule and train staff to implement maintenance plans.
Prepare a maintenance budget
Record inspection results, analyse the records and evaluate the success of
maintenance
Continuously update procedures and standards.
5.2 Maintenance and inspection
Maintenance Work equipment needs to be properly maintained so that it continues to
operate safely and in the way it was designed to perform. The amount of maintenance
will be stipulated in the manufacturers’ instructions and will depend on the amount of
use, the working environment and the type of equipment. High speed, high risk
machines, which are heavily used in an adverse environment like salt water, may
require very frequent maintenance, whereas a simple hand tool, like a shovel, may
require very little.
Figure 1. Typical maintenance notice
Maintenance management schemes can be based around a number of techniques
designed to focus on those parts which deteriorate and need to be maintained to
prevent health and safety risks. These techniques include:
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Preventative planned maintenance – which involves replacing parts and
consumables or making necessary adjustments at preset intervals, normally set
by the manufacturer, so that there are no hazards created by component
deterioration or failure. Vehicles are normally maintained on this basis
Condition based maintenance – this involves monitoring the condition of critical
parts and carrying out maintenance whenever necessary to avoid hazards which
could otherwise occur
Breakdown based maintenance – here maintenance is only carried out when
faults or failures have occurred. This is only acceptable if the failure does not
present an immediate hazard and can be corrected before the risk is increased.
If, for example, a bearing overheating can be detected by a monitoring device, it
is acceptable to wait for the overheating to occur as long as the equipment can
be stopped and repairs carried out before the fault becomes dangerous to
persons employed.
In the context of health and safety, maintenance is not concerned with operational effi-
ciency but only with avoiding risks to people. It is essential to ensure that maintenance
work can be carried out safely. This will involve:
Competent well-trained maintenance people
The equipment being made safe for the maintenance work to be carried out. In
many cases the normal safeguards for operating the equipment may not be suffi
cient as maintenance sometimes involves going inside guards to observe and
subsequently adjust, lubricate or repair the equipment. Careful design allowing
adjustments, lubrication and observation from outside the guards, for example,
can often eliminate the hazard. Making equipment safe will usually involve
disconnecting the power supply and then preventing anything moving, falling or
starting during the work. It may also involve waiting for equipment to cool or
warm up to room temperature
A safe system of work being used to carry out the necessary procedures to
make and keep the equipment safe and perform the maintenance tasks. This
can often involve a formal ‘permit to work’ scheme to ensure that the correct
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sequence of safety critical tasks has been performed and all necessary
precautions taken
Correct tools and safety equipment being available to perform the maintenance
work without risks to people. For example special lighting or ventilation may be
required.
5.3 Inspection under the provision and use of work
Equipment Regulations Complex equipment and/or high-risk equipment will probably
need a maintenance log and may require a more rigid inspection regime to ensure
continued safe operation. This is covered by PUWER 98, Regulation 6. PUWER
requires that where safety is dependent on the installation conditions and/or the work
equipment is exposed to conditions causing deterioration, which may result in a signifi
cant risk and a dangerous situation developing, that the equipment is inspected by a
competent person. In this case the competent person would normally be an employee,
but there may be circumstances like fairground equipment, where an outside competent
person would be used. The inspection must be done:
After installation for the first time
After assembly at a new site or in a new location and thereafter
At suitable intervals and
Each time exceptional circumstances occur which could affect safety
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Maintenance and Repair Report Format
Self-Check – 5 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
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Test I: Short Answer Questions
1. Why proper maintenance is required? (3 points)
2. List down the actions that can put preventive maintenance into practice. (5
points)
You can ask you teacher for the copy of the correct answers.
Answer Sheet
Information Sheet 6 - Monitoring and confirming process specification
6.1 Introduction
Modern countertop grain mills make it easy for anyone to grind fresh, flavorful flours.
There are dozens of flour mills from which to choose. Fortunately, the search for an
ideal mill can begin with three basic decisions: what power source to use, the
appropriate milling mechanism and the maximum flour temperature to tolerate. Many
mills are appropriate for family use as well as in a bootstrap business. The decision
comes down to price, quality, versatility and convenience features.
6.2 Power Source
Manual Mills: For the energetic, athletic, disciplined person, a manual mill (particularly
the large flywheel type) can be a superb choice, with a low chance of nutrient-damaging
heat buildup. But most manual mills require work, so be realistic — if there’s no flour,
there can be no bread.
Electric Mills: If the primary objective is getting the flour ground and the bread on the
table without any fuss, frills or fanfare, then an electric mill’s primary drawback — loss of
Score = ___________
Rating: ____________
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
You can ask you teacher for the copy of the correct answers.
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use during power outages — may be acceptably rare. The zippiest, cleanest, easiest
mills in this category are relatively inexpensive, and they do one heck of a job, then go
back in the cupboard.
Convertible Mills: Many mill manufacturers have devised ways to make their mills
convertible from manual to electric or vice versa, so grinding continues with or without
power. It is important to select a convertible mill that works properly in either mode
because some don’t.
6.3 Milling mechanisms
Each grain mill has some mechanism for crushing, beating or grinding grain into meal,
usually in a range of textures from coarse to fine. Some mechanisms are more versatile
than others: They grind hard, soft, oily or wet items. Aside from the increasingly popular
“oat roller,” two milling mechanisms dominate the home mill market: burr and impact.
Burr mills are the most common. They have two grinding plates, one fixed and the other
rotated by a power source. The grain is fed into a gap between the burrs, which are
grooved to aid the shearing and crushing of the grain. Composite stone burrs are
constructed by pressing natural or artificial stones (and sometimes metal cutting blades)
in a bed of cement. Metal burrs/plates, some of which are flat and some cone-shaped,
are constructed of hardened cast steel or other metal. Basically, stone burrs tend to
crush the grain, and metal burrs tend to break and shear it.
Self-Check – 6 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Short Answer Questions
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3. List down the two main power sources of feed mill. (5 points)
4. List down the three basic decisions for an ideal mill search can begin. (5
points)
You can ask you teacher for the copy of the correct answers.
Answer Sheet
Information Sheet -7 Removing fine bran from semolina and bran product
7.1 Fine tuning the purification process
In a wheat mill, purification is achieved when fine bran and germ are separated from
endosperm particles to increase the purity of coarse endosperm (farina or semolina). In
durum semolina production, purifiers are essential to finished product quality and work
by removing fine bran and compound particles (large endosperm with attached bran)
from the finished semolina. In a flour mill, the objective of the purification system is to
separate clean farina, or coarse endosperm, from fine bran or compound particles to
feed the primary reduction rolls. This purification step allows the miller to maximize
extraction of low ash, bright color flour. While a purifier is the most common component
of a mill purification system, purification can be achieved in all mills with and without
additional purification equipment.
7.2 Using Roller Mills and Sifter
Purification is achieved in the milling process by using roller mills and sifters. Using
smooth rolls to gently grind key collection stocks commonly referred to as Quality or
Score = ___________
Rating: ____________
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
You can ask you teacher for the copy of the correct answers.
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Sizings passages in most American flow diagrams, small bran and germ particles are
flattened while endosperm particles are further reduced.
The gentle compression from a smooth roll with low differential increases the particle
size of bran and germ allowing each to be removed with the top scalping sieves of the
sifter. Many soft wheat flour mills rely solely on purification from rolls and sifters since
the soft endosperm breaks down more easily into small particles or flour.
This milling characteristic of soft wheat yields few coarse particles, or farina, which
would be suitable for purification with the purifier, therefore making the use of purifiers
less effective. One challenge is managing the grinding practices as the natural tendency
is to grind too hard on these key passages, breaking the bran and germ and eliminating
opportunity to remove them in the sifter and purify the stock. In most other cases a
purifier is necessary to produce low-ash flour and bran-free semolina, and proper set-up
is important for optimal separation.
7.3 Stratification of the Stock
When using a purifier to separate good endosperm from bran and compound particles,
the key is proper stratification of the stock. Stratification, or layering of the stock in the
purifier, is achieved by combining a reciprocating or vibratory agitation with the gentle
upward flow of air evenly through the product. The principle of terminal velocity is the
resistance to air flow particles have depending on their shape. Irregularly shaped or flat
particles have greater resistance to air flow than round particles. Larger particles of
similar density will have greater resistance to air flow than smaller particles.
For a purifier to be effective, stock of similar-sized particles is fed from a sifter. The
stock has a range of particle shapes and densities. When the stock is exposed to the
mild agitation and upward air flow, lighter particles float to the surface and the heavier
particles will sink to the bottom. Small, heavier particles fall faster, allowing the purifier
to grade farina into particle size ranges for efficient grinding.
The smallest, cleanest farina falls through the air current and sieves at the front or head
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of the purifier, while slightly larger farina falls through the end of the purifier sieve deck.
The irregular shaped compound particles and flat bran particles float to the end of the
purifier decks and tail over. Controlling the air through the purifier is critical to its
operation. Stratification of material in the purifier is destroyed by intense agitation, often
the result of too much air being drawn through the mixture of particles. With too little air,
the stock will not separate.
A visual inspection by the miller of the stock feeding the purifier as compared to the
stock leaving the purifier can confirm that the stock is being properly stratified. The
figure on page 64 illustrates stock for a first purifier (P-1) from a first or second break
sifter using the most common triple deck purifier. When the stock in the purifier is
properly stratified, the first product through the head sieves will be the cleanest
endosperm and the smallest particle size. The product through the tail sieves will be
clean endosperm, but larger in particle size.
This happens as the larger particles of the same density have a lower terminal velocity.
As for the stock tailing over the three sieve decks, the stock tailing over the bottom
deck should look similar to the stock feeding the purifier. The stock on the top deck
should be the coarsest bran, and the middle should be smaller, but similar in purity
when compared to the top deck. This rule of thumb works well for break purifiers.
However, as the average particle size of material feeding a purifier gets smaller,
maintaining a good separation of stock in the purifier is more difficult.
7.4 Loading of Purifiers
Proper loading and clothing of the purifier sieves is critical to the effectiveness of the
separations made by the purifier. Purifier capacity is determined by the width of the
deck and is measured in pounds or kilogram per hour per inch or millimeter of deck
width. The load is very dependent on the particle size of the stock as well. Purifiers
must always be fed from a sifter or from another purifier. The larger the average
particle size, the greater the load can be to the purifier. However, to optimize the
separation from the purifier, a smaller micron range of the stock feeding the purifier is
preferred. Generally a range of 200 to 400 microns from the sifter is optimal.
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Purifiers can be classified in two general categories based on what type of mill stock is
feeding them. Break purifiers receive stock from break sifters. Generally, coarse
middlings or sizings stock come from primary breaks, but fine middlings from
secondary break passages may be sent to purifiers as well. Reduction purifiers receive
stock from sizings sifters or from other purifiers. The purifier clothing must be sized to
match the stock. As a general rule, the clothing of the first purifier sieve should be 2 to
four grit gauze numbers coarser (50 to 70 microns) than the sifter sieve clothing that
the stock passed over. The intermediate purifier sieves should be evenly spaced with
the last purifier sieve approximately two grit gauze sizes coarser than the sifter sieve
clothing which the stock came through.
7.5 Conditions for effective purifiers
For purifiers to effectively separate and grade stock, the balance of air and product must
be consistently maintained. This balance starts with the feeder gate to the purifier. The
stock must be fed across the entire width of the sieve and it must travel evenly down the
full length of the sieve. The purifier clothing on the sieves must be in good condition,
free of patches and holes. The sieve cleaners, either brushes or ball, must operate
effectively to keep the sieve surface free from buildup and blinding over. Air flow is
critical, and air will always flow to the path of least resistance. Any inconsistency in the
flow of stock or the condition of the sieves will result in inconsistency of air flow. To
check and maintain effective purification, sieves should be hand brushed weekly and air
chambers should be checked regularly for the build-up of dead stock.
7.6 Deciding on purification
Few modern flow diagrams have no purifiers in the process and many diagrams use
several purifier passages. There are several advantages and disadvantages to be
considered when deciding how to use purifiers in a mill flow. A significant advantage is
the ability to grade stock and balance the load to various roll passages while the mill is
operating. Unlike a sifter, purifier sieves can be pulled out and changed while the mill is
running under load. Purifier tips or valves can be adjusted as necessary to redirect
stock based on mill load or quality if there is a change in the wheat or mill environment
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impacting mill balance. Purifiers help to increase flour production of low ash flour at the
head end of the mill. By removing fine bran, purifiers enable the use of impact mills on
certain stock without significant change to flour quality. The use of purifiers also allows
for the production of high quality farina as a finished product if desired.
However, there are several disadvantages to using purifiers as well. As stated at the
beginning of this article, smooth rolls can serve the same purpose as purifiers in many
cases depending on wheat type and the quality desired of the finished flour. Purifiers
will dry out the stock if the environment of the mill is not controlled appropriately.
Purifiers require training for millers to understand how to monitor their operation and the
attention it takes keep the sieves clean and working properly.
Added maintenance, air and filter requirements, electrical usage and capital expense
must all be considered when deciding how much purification is needed to produce the
quality of flour desired.
Self-Check – 7 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test : Short Answer Questions
1. List down the two main power sources of feed mill. (5 points)
2. What is the objective of purification system? (5 points)
You can ask you teacher for the copy of the correct answers.
Answer Sheet
Score = ___________
Rating: ____________
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
You can ask you teacher for the copy of the correct answers.
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Information Sheet 8 - Retuning fine bran product to purification or scratch rolls
8.1 Break roll spirals.
The types of particle are separated one from the other according to size by scalping,
dusting and grading. The over tails of the wire scalping sieve (bran coats) become the
feedstock to the second break. The finer stocks are graded and conveyed to be purified
in preparation for appropriate further treatment on reduction mills, except for the flour,
which is a finished product and is retained for blending with other machine flours. The
feed to the subsequent breaks consists of the break stock scalped from the grind of the
previous break. The scraping action of the break rolls is achieved by a combination of
their fluted surface and the speed differential of 2.5:1 at which they run. The flutes run in
a spiral: 1 5 0 is typical for break rolls running at 550/220 in the first and second breaks
and 1:24 for subsequent breaks. Flutes vary in size from mill to mill, but on a 250 mm
diameter roll they might be:
1st break 3.24.1 per 10 mm;
2nd break 5.1-5.7 per 10 mm;
3rd break 6.4-7.0 per 10 mm;
4th break 8.6-9.6 per 10 mm;
5th break 10.2-10.8 per 10 mm.
Wear on flutes reduces their sharpness, leading eventually to the need for refluting, the
interval at which this occurs varying from about six months upwards. Many rolls run
sharp-to-sharp, but with new rolls, while the extreme sharpness is wearing off, the fast
roll may be run in the dull mode. Some millers consider that, if first break rolls are run
dull-to-dull, large flakes of bran are produced, while it is claimed that sharp-to-sharp
cuts the bran into small flakes which are difficult to clean. Dull-to-dull fluting tends to
produce more break flour than sharp-to-sharp at similar releases. In any of these
relationships the slow roll serves to ‘hold’ the stock while it is scraped by the fast roll
surface. As the bran passes down the break system, the gap between the rolls declines
appropriately to the thinner bran flakes. In each grinding stage the bran becomes
progressively cleaner until, following the last break grind, it can yield no more
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endosperm through further grinding. It may become the finished byproduct ‘bran’ at this
stage or it may be subjected to treatment in bran finishers. A bran finisher consists
essentially of a hollow cylinder, two thirds of which is perforated. Scalping’s are fed into
the horizontally disposed cylinder and finger beaters, attached to a central shaft, rotated
at high speed and the bran skins are propelled against the perforated cover. Some of
the remaining endosperm is rubbed off and passes through the apertures. Clean bran
over tails the machine. The through contain small fragments of bran and require further
sieving but, because they are ‘greasy’ and would blind plansifters, they are dressed on
special sifters such as vibratory sifters. Break release.
The break release throughs of the scalper cover) varies among mills. The criteria
determining selected proportions are:
The number of break stages;
The grist; larger releases on first break are typical for soft wheat’s, followed by
lower releases on succeeding breaks;
Specifications of the finished products, for example, higher early break releases
may be advisable when milling a large proportion of high grade flours. It is
generally considered desirable to release on breaks about 10% more stock than
is required in the straight-run (total) flour, subsequently rejecting the 10% from
the scratch and reduction systems as fine wheat feed. Typical break releases,
expressed as percentages of the individual break feeds, and of the feed to 1st
break; and the usual
8.2 Systems in flour mill process
8.2.1 Bran mill system
The function of bran mill is to peel wheat kernel and scrap endosperm from wheat
grains, and then use flat screen to classify the particles; the wheat residue, residue that
is connected with bran, and wheat core are delivered to purifying system for extracting
more pure wheat residue and core. The final bran milling system is mainly used to scrap
all the endosperm left on bran flake. There are totally 5 bran mills in this system: 1st and
2nd bran mill is mainly for crushing and extracting wheat residue and core, but the flour
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extraction rate is low; 3Bf bran mill is mainly for grinding the wheat residue that is
extracted from 2nd mill, while 3Bf is to grind the first layer screened material, and its flour
extraction rate is also low; the 4th bran mill can grind coarse and fine particles
separately. At the middle and end stages, there are bran brusher and bran finisher to
make sure bran purity and decrease power leakage.
8.2.2 Scratch mill system
The scratch mill in wheat flour mill process is to process the coarse particles from bran
mill, or endosperm that is connected with bran. Its grinding roller scraps lightly to
separate wheat bran from endosperm; after sieving, wheat core and coarse flour with
little bran are extracted, and then delivered into core mill system for extracting high
quality wheat flour. At the same time scratch mill system also extract a proportion of
flour.
The scratch system has 2 paths. The contacting length of scratch system grinding roller
is generally 0.8-1.2mm/ (100kg wheat*24h), which takes 7% to 10% of the whole purifier
grinding roller length. As this 300ton/d flour mill adopts hard wheat as raw material, it
applies the system of “first purifying, then wheat residue enters”. The main features of
this process are: wide range of purifying, high extraction rate of 1st grade coarse grain
particle, the material that enters scratch mill has similar quality and weight, and the
grinding rotation rate is suitable for processing wheat with high hardness.
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8.2.3 Purifying system
The purifying system in wheat flour mill process is used to purify the wheat residue, core
and hard coarse flour which were extracted from bran mill and scratch mill and divide
them into husk, endosperm with bran and pure endosperm participles by weight. The
pure wheat core is delivered to core milling system; wheat residue is delivered to
scratch milling system, while wheat flakes are delivered to tail mill or fine bran mill
system separately for processing. This can avoid bran and core from mixing into flour,
which also increases high quality flour extraction rate.
Those material enters purifier must be graded, and flour must be cleared away. The
material that enters the machine must be in uniform size, so that the operator can
choose proper sieve for purifier, and it shall also be equipped with adequate amount of
air flow to make sure purifying effect. Otherwise, if there is flour mixed in the material
that will enter purifier, or their particles have great disparity, it is hard to guarantee these
particles can evenly be spread on the sieve; as a result, the material may be pushed
slowly, and small particles may be sucked away with air, which greatly decreases
purifying effect.
There are totally 4 paths in purifying system. It utilizes the combined action of wind and
sieve to purify coarse flour and particle, which can better decrease product ash content
and increase yield.
8.2.4 Core mill system
The function of core mill system is to grind the relatively pure endosperm particles that
were gained from bran mill, scratch mill and purifying system into fine flour, while at the
same time decrease the breaking of wheat bran and wheat germ possibly. It can keep
the quality of wheat flour. After bolting (sifting), small bran flakes are delivered into tail
mill, the wheat core that has not been made into flour will be fed into next core mill for
grinding again, while the flour that meets requirements will be sifted out in time.
In order to improve flour quality, the core mill system in flour mill process adopts smooth
rolls, which decrease the breaking of starch granules in flour; at the same time the
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smooth rolls are processed by abrasive blasting, so that the roll will have rubbing to
materials, and grinding effect is improved to guarantee cortex integrity and flour quality.
As the flour is easily extruded into flakes between rollers and influence sieving effect of
plansifter, a wheat flour detacher is equipped in core mill system.
The incoming material of core mill system have non uniform quality: 1M, 2M and 3M
incoming material has relatively low ash content, so these 3 core mills grind a majority
of flour, which is also the main source of special purpose flour. The final stage of core
mill mainly produces wheat middling.
8.2.5 Tail mill system
Tail mill is usually designed at the milled or end of core mill. Its function is to process
tiny bran pieces from core mill, scratch mill, bran mill and purifying system, and also
small particle flour that is connected with bran. After the slight grinding of tail mill, and
sieving, different quality wheat core will be delivered into final core mill for grinding.
Self-Check – 8 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test: Short Answer Questions
1. ____________ is a finished product in the cereal mill operating
process. (3 points)
2. List down the systems in flour mill process and give explanation on
Purifying system. (7 points)
You can ask you teacher for the copy of the correct answers.
Answer Sheet Score = ___________
Rating: ____________
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
You can ask you teacher for the copy of the correct answers.
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Information Sheet 9 - Identifying, rectifying and reporting out-of-specification
Product/process outcomes
9.1 Introduction
Because of their extensive use as human foods, the safety and microbiology of cereal
grains and its products are highly concerned. The sources of the microbial
contamination of cereals are mainly contributed by the environment in which the crops
are grown, handled, and processed, which includes the air, soil, water, animals,
shipping containers, and processing equipment. Microbial food spoilage is defined as
deprive of good or effective food qualities as a result of microbial activity. Microbial food
spoilage can be identified and is visible in the form of surface slime or colonies, loss of
texture, or presence of by-products of microbial metabolism such as gas, pigments, off-
odours and flavours, or in combination of the above. However, this quality can be
subjective as each individual judges its unacceptability differently. In this study, the
microbiology of cereal grains and cereal products (dried cereal products, bread, pasta
and noodles) and its preservation are being studied.
9.2 Microbiology of cereals and cereal products
As mentioned previously, the microbiological contamination of cereal grains begins at
the growing phase of the grains. The intensity of the contamination can increase during
the growth and after harvest, resulting in the spoilage of the final products or worse,
induces foodborne illnesses in the consumers if appropriate control measures are not
taken.
9.2.1 Cereal Grains
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The spoilage of cereal grains is commonly associated with moulds, and some of these
moulds can be toxigenic. However, bacilli, some enteric bacteria, lactic acid bacteria,
and micrococci can also contaminate the crops which may cause problems in the
supply chain when products are made. The moulds affecting the crops can be
categorized into two groups: the field fungi and the storage fungi.
The ‘field fungi’, consist primarily of the genera Fasarium, Cladosporium, Alternaria, and
Helminthosporium, are moulds infecting the grains before harvest. At this stage, a large
number of such microorganisms are accumulated and these moulds grow on grains with
aw of 0.90 or higher or 18 to 30% moisture. On the other hand, the ‘storage fungi’ are
those that infect post-harvest grains, consist primarily of the genera Rhizopus,
Aspergillus, Penicillium, Mucor, and Wallemia growing at low moisture contents (14 to
16%).
Under favourable growth conditions, these moulds can produce mycotoxins, such as
aflatoxins, nivelanol, fumonisins, and deoxynivalenol. Mycotoxins are difficult to be
completely removed by processing treatments used for cereals. Therefore, it is very
crucial to control the prevalence of mycotoxin production to avoid food poisoning in the
consumers. The presence of certain bacteria and fungi can cause crop diseases in the
plants, which can lead to spoilage of the harvested grains and thus reduced crop yields.
Besides direct damage by the fungal growth, it can also results in the occurrence of
chemical (by enzyme of fatty acid production) or physical (by spontaneous heating due
to fungal activity or moisture and heat from insect contamination) damage in the grains.
9.2.2 Dried cereal products
Breakfast cereals, snack foods, oatmeal, rice cakes, and infant cereals are examples of
dried cereal products that are typically ready to eat (RTE) without the need of further
cooking, though some are optional to be heated with added hot water or milk. Dried
cereal products have water activity <0.5 which can inhibit the proliferation of most
microorganisms except moulds, thus reducing the possibilities for the occurrence of
microbiological hazards. In relation to that, foodborne illnesses associated with cereals
are less common as long as proper storage practices are followed to ensure the
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exclusion of water, insects, birds, and rodents. In contrast, Bacillus spp. may grow if the
water activity is favourable for growth.
On the other hand, the contamination can be from the environment or the ingredients. If
the raw grains are already contaminated with the production of mycotoxins from fungi, it
is quite likely that the cereal products are to contain mycotoxins too. Thus, tests for
mycotoxins are appropriate in cereal products. On the other hand, United States
Centers for Disease Control and Prevention (CDC) also reported two Salmonella Agona
outbreaks in 1998 and 2008 associated with breakfast cereals, in which the
investigations revealed that the cause of these outbreaks was related to the
contamination of the processing line in the manufacturing plants. In terms of microbial
spoilage, it is less likely to occur in dried cereal products due to its low water activity
unless the other ingredients added such as nuts and cocoa are contaminated.
9.2.3 Breads
Lactic acid bacteria may grow and contributes to the sourness in raw bread dough by
producing lactic acid as end products. A notable point is that Salmonellae and Bacillus
cereus may also be present in the raw dough. However, this will not be a major problem
as these bacteria can be destroyed when the dough is cooked at high temperatures to
attain its desired texture, colour, and structure. In addition, this process also dehydrates
the surface of the breads which in turns inhibits the growth of microorganisms on the
surface. Though baking can destroy the moulds in dough, recontamination can still
occur. The water activity of bread which is higher than 0.96 and with pH of about 5.5 to
6 gives favourable conditions for the growth of moulds. These moulds can be a great
hazard to the consumers as they can produce mycotoxins
9.2.4 Pasta and noodles
Pasta and noodles are categorized into two groups: fresh and dry pasta. Dry pasta is
made by mixing finely grounded semolina flour and water into a paste and then form
into the desired pasta shapes. This type of pasta has a long shelf life at ambient
temperatures due to its low moisture content resulted from the drying process at low
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temperature that lasts for several days. In contrast, fresh pasta has an extra ingredient
egg incorporated in the dough, giving a higher water activity as compared to dry pasta.
Since dry pasta has low water activity, its microbial hazards and spoilage are of less
concerned, except if the flour used is contaminated with mycotoxins production by
moulds.
Self-Check – 9 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test: Short Answer Questions
1. The sources of the microbial contamination of cereals are mainly contributed by
the environment. Give further explanation. (7 points)
2. What is the consequence of the spoilage of the final products? (3 points)
You can ask you teacher for the copy of the correct answers.
Answer Sheet
Score = ___________
Rating: ____________
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
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Information Sheet 10 - Maintaining the work area with housekeeping standards
10.1 Introduction
Effective housekeeping can eliminate workplace hazards and helps get the job done
easily and properly. A good housekeeping program plans and manages the orderly
storage and movement of materials from point of entry to exit. It includes a material flow
plan to ensure minimal handling. Worker training is an essential part of any good
housekeeping program. They should be reporting any unusual conditions or hazards as
well as obeying posted warning signs. The final addition to any housekeeping program
is inspection. It is the only way to check for deficiencies in the program so that changes
can be made.
10.2 Floors and other areas
Clean up spills such as oil on floors immediately. Floors should be free of debris and
accumulations of dust. Areas that cannot be cleaned continuously, such as
entranceways, should have anti-slip flooring. Replace any worn, ripped or damaged
flooring that poses a tripping hazard. Any equipment or tools not in use should be
removed from the work area. In the yard area, cut down and remove weeds and brush
from around buildings. They can hide tripping hazards.
10.3 Maintain light fixtures
All buildings and yards should be adequately lighted. Dirty light fixtures reduce
essential light levels. Light fixtures in storage areas containing combustible materials
should be protected against breaking (i.e. explosion proof fixtures). Maintain lighting
evenly; shadows mixed with light spots may cause trouble for people with weaker
eyesight.
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10.4 Aisles and stairways
Aisles and stairways should be clearly marked and kept clear of objects that can cause
trips and falls. Aisles should be wide enough to accommodate people comfortably and
safely. Warning signs and mirrors can improve sight lines at blind corners. Properly
arranged aisles encourage people to use them so that they do not take "shortcuts" or
"bottleneck" storage. Stairways and aisles also require adequate lighting.
10.5 Spill control
The best way to control spills is to stop them before they happen. Regularly cleaning
and maintaining machines and equipment is one way to do this. Another is to use drip
pans and guards where possible spills might occur. When spills do occur, it is important
to follow cleanup procedures as indicated on the Material Safety Data Sheet. Spills
must be cleaned up immediately. Absorbent material is useful for wiping up greasy, oily
or other liquid spills. Used absorbents must be disposed of properly and safely.
10.6 Tools and equipment
Keeping tools neat and orderly can be very important to everyone's safety, whether in
the tool room, on the rack, in the yard, or on the bench. Returning tools promptly after
use reduces the chance of them being misplaced or lost. Workers should regularly
inspect, clean and repair all tools and take any damaged or worn tools out of service.
10.7 Maintenance
A good maintenance program provides for the inspection, maintenance, upkeep and
repair of tools, equipment, machines and processes. Maintenance involves keeping
buildings, equipment and machinery in safe efficient working order and in good repair.
This includes maintaining sanitary facilities and regularly painting and cleaning walls,
maintaining windows, damaged doors, defective plumbing and broken floor surfaces.
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10.8 Waste disposal
The regular collection, grading and sorting of scrap contributes to good housekeeping
practices. Allowing materials to build up on the floor wastes time and energy since
additional time is required for cleaning it up. Placing scrap containers near where the
waste is produced encourages orderly waste disposal and makes collection easier. All
waste receptacles should be clearly labeled (e.g., recyclable glass, plastic, metal, toxic
and flammable etc.) All waste containers should be emptied regularly.
10.9 Storage
Stored materials should allow at least one meter (or about 3 feet) of clear space under
sprinkler heads. Stacking cartons and drums on a firm foundation and cross tying them,
where necessary reduces the chance of their movement. Stored materials should not
obstruct aisles, stairs, exits, fire equipment, emergency eyewash fountains, emergency
showers, or first aid stations. All storage areas should be clearly marked by fire
prevention: flammable, combustible, toxic and other hazardous materials should be
stored in approved containers in designated areas that are appropriate for the different
hazards that they pose. All combustible and flammable material must be present only in
the quantities needed for the job and kept in safety cans during use. Oily or greasy rags
should be placed in a metal container and disposed of regularly.
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Self-Check – 10 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test: Short Answer Questions
1. What are the objectives of maintaining the working area? (5 points)
2. List down the idea support`s best way to control spills before they happen?
(5 points)
You can ask you teacher for the copy of the correct answers.
Answer Sheet
Score = ___________
Rating: ____________
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
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Information Sheet 11 - Conducting work with environmental standards and
legislative requirements
11.1 Introduction
Grain can be processed in many different ways depending on the type of raw material
and the end product. The techniques most frequently used are:
Milling to reduce grain to smaller particles including flour;
Malting by germinating seeds; and
Extracting soluble carbohydrates for brewing.
Most by-products are dry and environmentally benign. The manufacturing steps include
some or all of the following as indicated in the below diagram (Figure 1). At all
manufacturing step there is a possibility of key environmental, health and safety
risk/liability issues. They are product contamination, dust and aerosols, wastewater
discharge, solid Waste, etc. Therefore, following the environmental protection policy and
regulation for reducing sources of environmental risks is must.
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Figure1. Grain mill operation process
11.2 Fire and explosion risk reduction
Use all dust emission reduction techniques;
Improved removal of metal, stones and glass which can cause sparking;
Locate equipment within a lightweight building so that the roof and wall
cladding panels can act as explosion relief;
Fit silos and bins with explosion relief;
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11.3 Reduction of spoil and loss
Weather proofing windows, doors and other openings against pests and
water;
Controlling moisture content in grain storage;
Monitor product losses during processing operations;
Ensure organic waste is collected and stored separately from other waste to
enable composting and/or use for soil amendment, or use in energy
production;
Regular inspection should be carried out of all bulk containment on site to
prevent leakage and product loss;
Provision of secondary spill containment for storage and process vessels;
Select cleaning materials that do not have an adverse effect on the
environment;
Good housekeeping should be maintained at all times all areas.
The adoption of good cleaning and working practises as a routine will reduce
dour emissions and improve hygiene standards;
Provision of personal protective equipment (PPE) that is fit for the task to
prevent injury and maintain hygiene standards. Staff should be trained in the
correct selection, use and maintenance of PPE;
Train workers in correct use of machinery and safety devices;
Redesign manual processes to avoid heavy lifting/repetitive activities;
Install mechanical lifting aids where possible and rotate work tasks to reduce
repetitive activities;
11.4 People separation from moving equipment
Ensure that the process layout reduces opportunities for process activities
to cross paths;
Installation of safeguards on moving parts of conveyor belts and
packaging machinery to reduce risk of entrapment of employees;
Install walkways to separate people from vehicle movements to reduce
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risk of collision;
11.5 Social, Labor and Community Improvements
Implement a quality control plan including sampling procedures and
frequencies;
Analysis methods;
Destination of non-compliant product;
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Self-Check – 11 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test: Short Answer Questions
1. List down the techniques most frequently used in grain processing activity. (5
points)
2. Choose only three dust emission reduction means, then explain. (5 points)
You can ask you teacher for the copy of the correct answers.
Answer Sheet
Score = ___________
Rating: ____________
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
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Information Sheet 12 - Maintaining workplace records requirements
12.1 Introduction
Every employer covered by the Fair Labor Standards Act (FLSA) must keep certain
records for each covered work, exempt and nonexempt worker. Apart from the legal
implications, maintaining accurate and updated employee records helps employers
save time while performing administrative duties. These details can also come in handy
during the recruitment process, identifying gaps in skills, availability of resources or at
the time of separation. Everyone wants to stay organized as well as to increase
productivity at workplace or in office.
12.2 Records to be kept by employers
There is no required form for the records, but the records must include accurate
information about the employee and data about the hours worked and the wages
earned. The following is a listing of the basic records that an employer must maintain:
Employee's full name and social security number;
Address, including zip code;
Birth date, if younger than 19;
Sex and occupation;
Time and day of week when employee's workweek begins. Hours worked
each day and total hours worked each workweek.
Basis on which employee's wages are paid;
Regular hourly pay rate;
Total daily or weekly straight-time earnings;
Total overtime earnings for the workweek;
Overtime: Covered nonexempt employees must receive overtime pay for
hours worked over 40 per workweek.
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Hours Worked: Hours worked ordinarily include all the time during which
an employee is required to be on the employer’s premises, on duty, or at a
prescribed workplace.
Recordkeeping: Employers must display an official poster outlining the
requirements of the FLSA. Employers must also keep employee time and
pay records.
Child Labor: These provisions are designed to protect the educational
opportunities of minors and prohibit their employment in jobs and under
conditions detrimental to their health or well-being.
12.3 Enterprise coverage
Employees who work for certain businesses or organizations (or "enterprises") are
covered by the organization for which they are working. Even when there is no
enterprise coverage, employees are protected by the Fair Labor Standards Act
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Self-Check – 12 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test: Short Answer Questions
1. What is the importance of maintaining work place records? (5 points)
2. Which one of the following records is to be kept by employers? (5 points)
A. Employee’s full name and social security number,
B. Sex and occupation and Regular hourly pay rate,
C. Time and day of week when employee's workweek begins,
D. Basis on which employee's wages are paid,
E. All.
You can ask you teacher for the copy of the correct answers.
Answer Sheet
Score = ___________
Rating: ____________
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
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Operation Sheet 1- procedure for grinding the bore of a bushing
The following sequence is provided step-by-step for grinding the bore of a bushing in
order to attain correct procedure, follow these procedures.
Step-by-step procedure for grinding the bore of a bushing
Bolt internal grinding attachment to the wheel head on the universal tool and
cutter grinder.
Set up the workpiece in an independent chuck and check and adjust its
alignment, to rotate in the direction opposite that of the grinding wheel.
Mount the internal grinding attachment to the wheel head and adjust its position
so that the grinding wheel is centered vertically with the mounted workpiece.
True and dress the grinding wheel.
If two or more grinding wheels are used to complete internal grinding, true each
wheel after mounting it to the spindle of the internal grinding attachment.
Set the proper wheel speed on the grinding machine by adjusting the pulleys
and belts connecting the wheel spindle to the drive motor shaft.
The RPM is increased by placing a large pulley on the motor and a small pulley
on the attachment.
Set the proper rotational work feed. The speed should be 60 to 100 surface feet
per minute (SFPM).
Be sure sufficient clearance is allowed when setting the traversing speed so that the
grinding wheel will not strike any part of the workpiece or setup when the wheel is fed
into and retracted from the workpiece
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Operation Sheet 2- Steps of using cleaning hose and wet cleaning process.
Steps of using cleaning hose and wet cleaning process.
2.7 Safe operating procedures
Housekeeping
Do not:
Operate in poorly lit area.
Attempt to clear an auger while it is running.
Remove any covers or guards while the plant is running.
Allow children or inexperienced people to operate plant.
Allow spilt materials to accumulate near electric motors. Remove spilt
grain and dust as soon as the
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Operation Sheet 3- Reduction means of dust emissions
11.6 Means of dust emissions reduction
Enclosing and sealing plant and equipment to prevent escape and
accumulation of dust;
Use of doors/plastic strip curtains on building access points.
Redesigning processes to reduce free-fall distances and speed of movement
for grain and other dry products
Installing windbreaks and covers in outside handling areas;
Replace any external bulk storage areas with silos, fitted with alarms to
prevent overfilling;
Install a centralized piped vacuum cleaning systems;
LAP Test Demonstration
Name----------------------------------- ID------------------------ Date--------------------------------
Time started: ________________________ Time finished: ________________
Instructions: Given necessary templates, tools and materials you are required to
perform the following tasks within 1 hour. The project is expecting you
to do it.
During your work: You can ask all the necessary tools and equipment
Lap Test Title: Produce Tool Shanks for Milling Machines
Task Objectives / Demands: in accomplishing activities required for this project the
student will be able to: (During your work follow these steps)
LAP Test Demonstration
1 Apply procedure for grinding the bore of a bushing.
2 Perform steps of using cleaning hose and wet cleaning process.
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3 Determine reduction means of dust emissions.
LG #26 LO #3- Shut down the milling and purification process
Instruction sheet
This learning guide is developed to provide you the necessary information regarding
the following content coverage and topics:
Identifying shutdown procedures
Shut down process with workplace procedures.
Identifying and reporting maintenance requirements are
This guide will also assist you to attain the learning outcomes stated in the cover page.
Specifically, upon completion of this learning guide, you will be able to:
Identify shutdown procedures
Shut down process with workplace procedures.
Identify and report maintenance requirements are
Learning Instructions:
1. Read the specific objectives of this Learning Guide.
2. Follow the instructions described below.
3. Read the information written in the information Sheets
4. Accomplish the Self-checks
5. Perform Operation Sheets
6. Do the “LAP test”
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Information Sheet 1- Identify shutdown procedures
1.1 Introduction
The actions required by this procedure are essential to assure a safe shutdown and to
properly plan and allocate resources. Two types of utility shutdown are available. They
are emergency shutdowns and formal shutdowns.
1.2 Shutdown work identification
The work, which is to be carried, should be clearly identified. The work identification
depends upon following points:
The number of failures
The root causes of those failures
The maintenance costs associated with those failures
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The production costs associated with those failures - note that these may
incorporate more than just downtime costs.
Any safety or environmental implications associated with those failures.
1.2.1 Procedure for emergency shutdowns
Emergency shutdowns shall be done as follows:
The first responder shall immediately get him/herself and others out of harm’s
way, call the fire department or police if necessary. Notify the central call-in
desk, and begin taking whatever actions are necessary to mitigate damages.
If the first responder wasn’t the building Engineer the central call-in desk will
dispatch the building engineer to the scene.
For shutdowns within utility plants or in the central distribution, the ranking
person present shall assume authority. For shutdowns within buildings other
than utility plants, the ranking person present shall assume authority. The
only exception is if the shutdown requires a fire department or police
response, an on-scene incident commander shall assume authority. The
person who assumes authority shall direct all actions to eliminate the
immediate risk. All factory employees shall cooperate with and assist the
person having authority.
The person in charge is authorized to call in additional factory employees if
he/she deems it necessary to protect the facilities and/or the occupants work.
When the immediate risk has been controlled, the person who lead the
shutdown effort shall immediately notify his/her supervisor.
The supervisor shall designate responsibilities for clean-up or other activities
that need to continue and shall report the incident to the next level supervisor
and to Directors or Division of Environmental Protection (DEP). These
reports will either be done immediately or if the shutdown was done outside
normal business hours and no immediate hazard exists, the report can be
done first thing on the next business day.
The incident shall be reported up the chain of command to the chiefs. The
applicable branch chief will assume, or designate somebody else to assume
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authority for follow-up work and the authority will involve all other necessary
persons and/or groups in resolving the situation which created the
emergency.
Within one business day, the applicable branch chief shall notify the director,
the situation including cause, action taken, damage and current status.
1.2.2 Procedures for formal shutdowns
All formal utility shutdown requests shall be electronically routed to a queue and shall be
pulled from the queue by the responsible personnel. The person who pulls the queue is
responsible for evaluation of the queue, notification of the facility users, planning,
communication with the responsible section, facility manager and others and in general
identifying and doing or delegating and managing whatever tasks are necessary to
make the shutdown run smoothly. The responsible person shall identify and implement
(delegate, manage or provide oversight on) any unique requirements. The responsible
person may request that to manage the implementation of a unique requirement. For
example, the chief person may request that the person who arrange for temporary
services to the affected area so the critical functions can continue uninterrupted.
1.2.3 Procedure for minor formal shutdowns
The responsible person shall discuss the shutdown with the building
engineer before submitting it and both will have agreed that the shutdown
is minor. Request shall be submitted through the shutdown webpage no
less than two working days in advance and shall be in the “approved”
status for no less than one day.
When a request is entered at the webpage, it goes into a queue. All
shutdown requests that are labeled as minor shall be taken from the
shutdown queue by building maintenance within a day.
1.2.4 Procedure for major formal shutdowns
The project officer shall submit shutdown requests through the shutdown
webpage no less than 18 calendar days in advance. The request shall be
in “approved” status for no less than 14 days.
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For any work involving underground utilities, the project officer shall
discuss the project with the Director of the Central Systems Team and the
Director shall assign a contact person for the project. Whenever
considering an underground utilities shutdown, the project officer must
discuss the shutdown with the contact person before submitting the
request. The Central Systems Team contact person shall begin
scheduling underground utility shutdowns after discussing with the project
officer. The Building Maintenance Team shall notify the Central Systems
Team when the request has been received electronically.
For all major formal shutdowns, upon entry in the web based system, the
system will automatically put the request in “submitted” status and move it
to a queue. Support Services Team (SST) within the maintenance
services branch shall pull all fire alarm and sprinkler requests from the
queue for processing. Building Maintenance Team shall pull all other
request. Building Maintenance shall coordinate with the Utilities
Operations Branch for underground utilities shutdowns. Whichever
shutdown group pulls the request shall plan the shutdown and move the
request to the “approved” status no less than 14 days in advance of the
event. Each group shall have internal office procedures covering how
Self-Check – 1 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test: Short Answer Questions
1. How many types of utility shutdowns do you know? Would you list down them
here? (5 points)
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2. Which one of the following actions is intimately related to emergency shutdowns?
(5 points)
A. The first responder shall immediately get him/herself and
others out of harm’s way.
B. Electronically routed to a queue.
C. Responsible person shall identify and implement any
unique requirements.
D. None.
You can ask you teacher for the copy of the correct answers.
Answer Sheet
Information Sheet 2- Shut down process with workplace procedures
2.1 Introduction
All requests for formal scheduled utility shutdowns shall be entered. A specific date
must be requested. Safe use shutdown process of machines (mill, ball, pedestal
grinding) are indicated here bellow.
2.2 Workshop machines – mill shutdown process
Keep all guards in place while operating the machine.
While operating the milling machine allow no one else to touch it.
Keep hands away from moving cutting tools.
Score = ___________
Rating: ____________
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
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Do not make measurements of the stock while the milling machine is
powered.
Do not allow large quantities of chips to accumulate around the work piece or
machine table. After stopping the machine, use a brush or rag to remove all
excess chips from the mill bed and stock.
Use a rag or Kevlar gloves to handle sharp cutting tools.
Cutting tools must be securely fastened in the machine spindle with the
proper accessory. Never try to tighten cutting bits or tools by hand.
Do not power the machine to tighten or loosen cutting bits or tools.
Work pieces and stock must be rigidly fastened to the mill bed with clamps, a
vise, or special fixtures.
Use appropriate speeds and feeds for the type and size of cutter being used
and the material being machined.
Make sure the cutting tool is clear of the work piece before starting the
machine.
2.3 Workshop machines - pedestal grinder shutdown process
Inspect the wheels before turning on the power. Do not use wheels that are
chipped or cracked.
Stand to one side of the wheel when turning on the power.
Keep the tool rest as close to the grinding wheel as possible without touching
it. The tool rest must be minimally within 1/8th of an inch of the grinding
wheel.
Prior to starting the grinder, ensure the tang at the top of the wheel opening is
located within ¼ inch of the wheel.
Prior to starting the grinder, ensure guards enclosing the outside of grinding
wheel are in place.
Prior to adjusting the work rest or tang, unplug the power to the grinder from
the wall receptacle.
If the grinder is hardwired into a box, Lock-out/Tag-out.
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Be alert and cautious when a grinding operation requires locating fingers
close to the wheel.
Feed the stock into the wheel with light to medium pressure. Do not force the
piece.
Do not use the side of the grinding wheel to shape stock.
Stand erect in front of the grinder with both legs straight and slightly apart.
Avoid stooping or leaning into the machine.
2.4 Normal shutdown sequence of mill and grinding circuit
Shut off cyanide metering pump.
Put weight controller into manual mode and turn controller output to 0%. Run
the ball mill for 15 – 30 minutes.
Put density controller into manual mode, set output to 0%.
Put flow controller into manual mode and set output to 0%
Turn off ball mill lime timer.
Disengage ball mill clutch. The mill conveyor will automatically stop due to the
interlocks between the clutches or cyclone feed pumps and the conveyer.
Shutdown ball mill motor.
Shutdown ball mill lube system.
Drain and flash the cyclone feed pump, line and pump box if the shutdown is
longer than 1-2 hours. Once the pump and system have been drained, shut
off the cyclone feed pumps and close the gland seal water shut off valve to
the cyclone feed pump.
Close the air block valves to the cyclones and the cyclone feed pump box,
and shut off valves on all barren lines.
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Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Self-Check – 2 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
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Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Test: Short Answer Questions
1. Lists down the machines you had been observed their Safe use shutdown
process. Submit their diagram to your instructor too.
2. While operating the milling machine allow no one else to touch it. Discuss.
You can ask you teacher for the copy of the correct answers.
Answer Sheet
Score = ___________
Rating: ____________
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
You can ask you teacher for the copy of the correct answers.
Page 127 of 137
Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Information Sheet 3- Identifying and reporting maintenance requirements
3.1 Introduction
It is known that best practices for milling machine maintenance are lubrication, cleaning
and daily inspection. One way to keep tools for machine services in good condition is by
making sure that they are adequately lubricated. Another requirement for keeping a
piece of machinery usable is making sure that is properly cleaned after use. By keeping
up with daily inspections, you can prevent a problem from happening right from the get-
go.
3.2 Daily inspections
A daily inspection is especially important if you’re using your milling machine on a daily
basis. If something is amiss and you start using your machine without thoroughly
inspecting it first, you may be in for a world of trouble. If something looks fine one day
and operates wrong the next, an inspection can catch the issue before it’s too late. If
you find any problem with your tool but are unsure of how to fix it, reach out to your
machine shop immediately for the fix or other tips. But until then, make sure you’re
practicing good maintenance with all of your machine tools.
3.3 Maintenance recommendation
Maintenance recommendations are based on industry standards and experience in
reclamation facilities. However, equipment and situations vary greatly, and sound
engineering and management judgment must be exercised when applying these
recommendations. Other sources of information must be consulted (e.g., manufacturers
recommendations, unusual operating conditions, personal experience with the
equipment, etc.) in conjunction with these maintenance recommendations. Classifying
level of maintenance, while reporting for maintenance requirement, as here indicated
below, is highly useful.
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Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
3.3.1 Preventive maintenance
Preventive maintenance (PM) is the practice of maintaining equipment on a regular
schedule based on elapsed time or meter readings. The intent of PM is to “prevent”
maintenance problems or failures before they take place by following routine and
comprehensive maintenance procedures. The goal is to achieve fewer, shorter, and
more predictable outages.
Some advantages of PM are:
It is predictable, making budgeting, planning, and resource leveling
possible.
When properly practiced, it generally prevents most major problems, thus
reducing
forced outages, “reactive maintenance,” and maintenance costs in
general.
It assures managers that equipment is being maintained.
It is easily understood and justified.
Preventive Maintenance does have some drawbacks:
It is time consuming and resource intensive.
It does not consider actual equipment condition when scheduling or
performing the maintenance.
It can cause problems in equipment in addition to solving them (e.g.,
damaging seals, stripping threads).
Despite these drawbacks, PM has proven generally reliable in the past and is still the
core of most maintenance programs.
3.3.2 Reliability-centered maintenance
Reliability-centered maintenance (RCM) programs are gaining in popularity and have
been piloted in a few reclamation power facilities with good results. The goal of these
programs is to provide the appropriate amount of maintenance at the right time to
prevent forced outages while at the same time eliminating unnecessary maintenance.
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Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Implemented properly, RCM can eliminate some of the drawbacks of PM and may result
in a more streamlined, efficient maintenance program. RCM seems very attractive in
times of diminishing funding, scarcity of skilled maintenance staff, and the pressure to
“stay online” due to electric utility industry deregulation.
Some features of RCM are:
It may be labor intensive and time consuming to set up initially.
It may require additional monitoring of quantities, like temperature and
vibration, to be effective. This may mean new monitoring equipment with
its own PM or more human monitoring with multiple inspections.
It may result in a “run-to-failure” or deferred maintenance philosophy for
some equipment which may cause concern for some staff and managers.
It may require initial and later revisions to the maintenance schedule in a
“trial-and-error” fashion depending on the success of the initial
maintenance schedule and equipment condition.
It should result in a more manageable maintenance workload focused on
the most important equipment.
RCM is not an excuse to move to a “breakdown maintenance” philosophy or to
eliminate critical PM in the name of reducing maintenance staff/ funding.
3.3.3 Condition-based maintenance
This program relies on knowing the condition of individual pieces of equipment.
Some features of condition based maintenance (CBM) include:
Monitoring equipment parameters such as temperatures, pressures,
vibrations, leakage current, dissolved gas analysis, etc.
Testing on a periodic basis and/or when problems are suspected such as
Doble testing, vibration testing, and infrared scanning.
Monitoring carefully operator-gathered data.
Securing results in knowledgeable maintenance decisions which would
reduce overall costs by focusing only on equipment that really needs
attention.
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Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Drawbacks to CBM include it being very difficult and expensive to monitor some
quantities. It requires knowledgeable and consistent analysis to be effective; and also
condition monitoring equipment and systems themselves require maintenance. Because
of these drawbacks, it is nearly impossible to have an entirely CBM program.
3.3.4 Combination of condition-based and preventive maintenance
A combination of CBM and PM is perhaps the most practical approach. Monitoring,
testing, and using historical data and PM schedules may provide the best information on
when equipment should be maintained. By keeping accurate records of the “as found”
condition of equipment when it is torn down for maintenance, one can determine what
maintenance was really necessary. In this manner, maintenance schedules can be
lengthened or perhaps shortened, based on experience and monitoring.
Page 131 of 137
Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Table 1. Pre and after maintenance requesting and reporting format, respectively
Page 132 of 137
Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Self-Check – 3 Written test
Name…………………………………………… ID………………………… Date…….
Directions: Answer all the questions listed below. Examples may be necessary to aid
some explanations/answers.
Test I: Choose the best answer
1. Which one of the following level of maintenance is time consuming and resource
intensive?
A. Condition-based maintenance
B. Preventive maintenance
C. Reliability-centered maintenance
D. None
2. A _______________ is especially important if you’re using your milling machine
on a daily basis.
You can ask you teacher for the copy of the correct answers.
Note: Satisfactory rating - 3 points Unsatisfactory - below 3 points
You can ask you teacher for the copy of the correct answers.
Page 133 of 137
Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Page 134 of 137
Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Page 135 of 137
Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
Reference Materials
Book:
1. Erik Oberg, Franklin D. Jones, Holbrook L. Horton, and Henry H. Ryffel,
“Machinery’s Handbook”, 27th Edition, Industrial Press, Inc., New York, NY, 2004
2. Helmi A. Youssef and Hassen El-Hofy, “Machining technology, Machine tools
and operations”, Taylor & Francis Group, Boca Raton, London, New York, 2008
3. Fundamentals of machine tools, Training Circular No. 9-524, headquarters
department of the army, Washington, DC, 29 October 1996
4. Shafizan Bt. Shariffuddin School of Manufacturing Engineering UniMAP
5. Inspection of Metals—Understanding the Basics, Copyright © 2013 ASM
International F.C. Campbell, editor, All rights reserved www.asminternational.org
6. Machining and Machine Tools by A. B. Chattopadhyay.
7. Metal Cutting: Theory and Practice by A. Bhattacharya.
8. Adams, M. & Moss, M. 2008, ‘Microbiology of primary food commodities’, in Food
Microbiology, 3rd edition, pp. 119-157
9. Bullerman, L.B. & Bianchini, A. 2011, ‘The microbiology of cereals and cereal
products’, Food Quality & Safety Magazine, February/March.
WEB ADDRESSES
1. ISO 9000:2005 Quality Management System – Fundamentals and Vocabulary
2. http://www.qualitygurus.com/courses/mod/forum/discuss.php?d=1557
3. http://www.iitg.ac.in/spal/Methods%20of%20mounting%20of%20jobs%20and%20c
utting%20tools.ppt
4. http://www.iitb.ac.in/safety/sites/default/files/Machine%20Safety_0_0.pdf)
5. https://www.fda.gov/media/109408/download
6. https://www.flexiblemachining.com/pdf/quality_policy.pdf
7. file:///C:/Users/pc/Desktop/SNE%20Post%20harvest%20Curricul%20OMP/Cereals
%20POST-HARVESTING%20PROCESSING.pdf
8. https://productionengineering08.blogspot.com/2008/08/5-basic-milling-
operations.html
9. Marleeta F. Basey, 2015. Choosing the Right Countertop Grain Mill
Page 136 of 137
Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
AKNOWLEDGEMENT
We wish to extend thanks and appreciation to the many representatives of TVET
instructors and respective industry experts who donated their time and expertise to the
development Teaching, Training and Learning Materials (TTLM)
We would like also to express our appreciation to the TVET instructors and respective
industry experts of Regional TVET Bureau, TVET College/ Institutes, Bishoftu
Management institute, BEAR II UNESCO project and Federal Technical and Vocational
Education and Training Agency (FTVET) who made contributions for the development
of this curriculum with required standards and quality possible. This Teaching, Training
and Learning Materials (TTLM) was developed on October 2020 at Bishoftu, bishoftu
management institute.
Page 137 of 137
Federal TVET Agency
Author/Copyright TVET program title- Cereal processing
Level -2
Version -1
October 2019
The trainers who developed the learning guide
N
o
Name Qualifi
cation
Educational
background
Regio
n
College Mob.no E-mail
1 Shiferaw
Negassa
(Phd)
Phd Plant science
(BSc),
horticulture
(MSc),
agronomy and
crop
physiology(Phd)
Oromia Holeta
satellite
college
0911913680 [email protected]
2 Tesfaye
Mekuriyaw
B Food science
and technology
Addis
Ababa
Kolfe
industrial
college
0927785174 Tesfayemekuriyaw48@gmail
.com
3 Moti Taye A Plant science Oromia Bako
College
0921801540 [email protected]
4 Adamu
Bekena
B Food
technology and
process
engineering
Addis
Ababa
Yeka
industrial
college
0988620906 [email protected]
5 Fistum FTA
facilitator