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SRI LANKA INSTITUTE of ADVANCED TECHNOLOGICAL EDUCATION
Training Unit
Electrical MaintenanceTheory
No: MS 004
INDUSTRIETECHNIKINDUSTRIETECHNIK
Automotive Engineering
Instructor Manual
Electrical and Electronic
Engineering
Instructor Manual
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List of Contents Page
Introduction 3
1. Definition 41.1. Breakdown Maintenance 51.2. Preventive Maintenance 51.3 Condition-Based Maintenance 62. Maintenance Philosophies 72.1 No Maintenance 82.2 Breakdown Maintenance 92.3 Preventive / Planned Maintenance 102.4 Predictive / Condition Based Maintenance 113. Goals Of Maintenance 143.1 General 154. The Position Of Maintenance Within A Company 165. Current Practical Situation Of Maintenance Management 176. Increasing Complexity Of Maintenance Services 187. Maintenance Strategy 197.1 Increasingly Stringent Safety Requirements 207.2 Stricter Environmental Regulations 207.3 Maintenance Orientated Design 207.4 Relative Increase In Knowledge 217.5 Shrinkage Of Time-Intervals 21
7.6 Shorter Utilization Time Of Systems, Process And Programs 217.7 Shorter Innovation Period 217.8 Manifold Combinations Possible 228. What Is Inspection (Condition Monitoring) 239. The Significance Of The Application Of Inspection Systems 2410. Reasons For Machinery Failure 2511. Total Cost Of Maintenance 2612. Maintenance Activities
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INTRODUCTION
For the most part, isn't maintenance still as a necessary evil or as an extension ofproduction? Don't maintenance departments hold a relatively high degree ofresponsibility yet have very little influence when important decisions are made?
These common attitudes will hardly enable companies to meet the challengesconfronting them in the future.
There are manifold reasons why maintenance in practice is not usually accorded theimportance it deserves. These range from insufficient knowledge of this specializeddiscipline to a lack of appreciation for maintenance activities and all the way tofailure to recognize the close ties between production and maintenance.
It is important that company management will acknowledge the steadily risingimportance of maintenance. Maintenance will in fact become a decisive factor inproduction.
More and more industries are employing condition-monitoring programs in theirmaintenance strategies to increase plant equipment availability.
This presentation will describe the difference between condition monitoring and othermaintenance philosophies and their development over the years.
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1.1 DEFINITION
The maintenance strategy is an object-related procedure, which specifies individualmaintenance activities, i.e. content, method and scope, to be carried out atpredefined intervals. If this procedure is defined by optimalization criteria then onerefers to an optimal maintenance strategy.
A review of the maintenance strategy over the course of time should begin before1970. At that time, the area maintenance foreman was the dominant figure in the
maintenance world.
He determined when and how a repair would be carried out based purely on hisown personal experience - normally after the damage had occurred - and alsodecided where and when plant improvements would be carried out.
Costs were irrelevant, budgeting and cost control was done but only in a very limitedway.
Many companies still follow the strategies of the 50's and 80 's for the most part,so-called unplanned or breakdown maintenance.
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1.1 Breakdown Maintenance
Using this method Planning costs are fairly low. However, work can only be planned afterdamage has occurred.
This method can resultin:
0 high breakdown rate0 considerable amount of consequential damage0 longer preparation time0 time-consuming spare parts ordering procedures0 inefficient use of resources (personnel, material, time, funds)
Naturally, this procedure is still worthwhile for some components but the percentageof breakdown maintenance should be very small
Companies, which recognized that this strategy was not efficient enough for theirplants moved one step further, to preventive maintenance.
1.2 Preventive Maintenance
A method, which was first applied in the airline industry, is based on regularreplacement or repair of parts based on experience, without taking the actualcondition of the part into consideration.
This had the following advantages:
0 reduction of the breakdown rate0 accurate planning of the maintenance activitiesO precise control of resources0 lower damage costs0 increased safety
However, there were still some disadvantages to be considered:
O higher consumption and costs of spare parts0 Inefficient use of spare parts and personnel due to too frequent replacements
and repairs
The exclusive use of this method like it was the case in the 1970s was thus veryexpensive for most companies, but preventive maintenance nowadays is still anecessity for equipment, which should provide 100% availability and safety.
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Finally, due to cost considerations, further development led to condition-basedmaintenance.
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1.3 Condit ion-based Maintenance
Maintenance activities were enhanced to include constant monitoring of equipmentand parts. The results of this monitoring are decisive factors in when a part shouldbe replaced or repaired.
The advantages and this method are obvious:
O selective planning and resource utilizationO low spare part costsO constant, up-to-date knowledge of the equipment condition
These and other advantages clearly justify additional personnel costs for inspectionand increased planning.
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2. Maintenance Philosophies
The following diagrams show the effect of different maintenance philosophies on
equipment life.
A . . . . . no maintenance
B . . . . . breakdown or unplanned maintenance
C . . . . . preventive or planned maintenance
D . . . . . predictive or condition based
maintenance
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2.1 A. NO MAINTENANCE
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2.2 B. BREAKDOWN MAINTENANCE
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2.3 C.PREVENTIVE / PLANNED MAINTENANCE
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2.4 D. PREDICTIVE / CONDITION BASED MAINTENANCE
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Due to the fact that the "no maintenance" strategy as such no longer exists, three
basic equipment maintenance philosophies remain to be applied.
Breakdown Maintenance (run to failure) "Running till breakdown occurs". This
strategy will be followed if breakdown costs are less than costs of other
strategies.
Preventive Maintenance
"Changing parts periodically". This strategy will be followed if condition monitoring
is impossible or uneconomic or breakdown costs are higher than replacement
costs.
Predictive Maintenance (condition monitoring) 'Planned replacements prior to
breakdown expected due to results of regular checks".
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Most machinery failures are predictive; therefore a good, well-selected monitoringprogram provides the basic tool for predictive maintenance.
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GOALS OF MAINTENANCE
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GENERAL
The corporate function of the maintenance department is to ensure that thetechnical facilities are in working order. Maintenance economy is defined by thegoal of minimizing the overall costs arising from the direct and indirect maintenance
costs. This goal is achieved by investing in information systems and the resultingplan ability. Today, of course, one is seldom in a position to apply this theoreticalknowledge as a management tool in practice. The reason for this is the difficultadditional collection and preparation of the respective data, which would have to beextensive enough to demonstrate an empirical relationship between the individualfactors with sufficient accuracy.
Progress towards optimization can be achieved, however, through continualcomparison of the costs of in-house services as well as the prices of contractedservices and the corresponding market trends. By suitably depicting the cost ofmaintenance activities, it is possible to determine the optimum capacity of thein-house maintenance department as well as the share of externally contractedservices.
Before the corporate objective for the plant maintenance sector is defined, anumber of maximization and minimization targets are listed, which are of highestpriority and are frequently cited in maintenance literature and practice.
Several frequently-mentioned targets are:
o cost minimizationo maximum plant availabilityo maximization of reliabilityo economical plant maintenance
o maximization of service life by preserving the value of fixed assets.
In addition to these individual targets, certain target-groups are also indicated, suchas:
0 optimization of profit0 optimization of service life0 optimization of maintenance costso ratio of preventive maintenance cost to cost of expected damage is
reasonable
From an economic viewpoint, the partial goals are always derived from theoverriding corporate goal of profit maximization and can be summarized into twoprimary goals of maintenance:
Optimization of Plant Availability
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Minimization of the Total Cost ofMaintenance
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4. THE POSITION OF MAINTENANCE WITHIN A COMPANY
As a result of technical developments and cost trends the significance ofmaintenance and the value attributed to ft is being increasingly recognized andacknowledged. Solutions have been developed by companies themselves, as well
as by external institutions, to put maintenance - whose status as an equal andoften-critical corporate element is by now uncontested - in an organizationalposition to perform its manifold technical and economic functions.
But one cannot help feeling, as one examines companies and maintenancedepartments and follows relevant literature, that maintenance is still in anunpleasant position; a position from which it can only extract itself with great effortA real breakthrough to the desired status has not been possible so far, or has beenonly partially successful. The uneasiness of the maintenance experts can beattributed to the fact that they were not able to keep pace with the general technicaland economic developments using the means and resources available to them.The routes taken to bridge the growing discrepancy were not always the best
Developments and Trends So Far
It was not all that long ago that production plants were generally wage-intensiveand equipped only with relatively simple machines. At that time, it was frequentlypossible to bridge machine operations in the event of a breakdown by increasingthe manpower. In an emergency, there were other machines and time, space,and/or capacity buffers to fall back on, without having to tolerate appreciablelosses. The demands placed on the maintenance team were relatively low.Things changed as machine-intensive factories separated production more andmore from manual labor. Larger, compacter, and more complex technical systemsreplaced simple machines. Investments rose along with the quantities producedand the possibilities to compensate and by-pass became more limited. Theproduction figures were decisively influenced by the operational reliability of theplants and breakdowns caused losses, which degreased the profits of thecompany.
At this stage of development the traditional maintenance organizations reached thelimits of their capability. It was the end of "management by foreman", based onintuition, personal initiative and improvisation, which had been common and hadfulfilled the requirements of the times.
Further mechanization and automation of production resulted in an almost totaldependency on machines. The tasks of operations personnel are limited to
operation and monitoring. High output levels, favorable profits, and low prices/unitcan only be achieved if the production plants function well. With increased in Tedinking of plants, there is also greater probability of a breakdown and greatertechnical and financial losses are expected as a result.
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5. CURRENT PRACTICAL SITUATION OF MAINTENANCEMANAGEMENT
The situation described here is based on studies carried out in companies as wellas discussions with maintenance experts in scientific and practical fields.
Misjudgment and Strategic Error of Corporate Management
The importance of maintenance within a company is generally underestimated. Onlyin exceptional cases is there Gear targets and long-tern strategies for maintenance.This permits considerable freedom of action and has created many weak points,which have been known for years but have not yet been eliminated.
Uncritical Ordering Att itude by the Client (Production)
Overvalued - too tight - repair deadlines lead to a high percentage of immediate
maintenance measures and consequently to great requirements for on-call services.Safety consciousness is exaggerated. In part, cost consciousness is verynon-discriminating; particularly as a sufficiently detailed overview of maintenancecosts and trends can often not be given.
Lack of or Inadequate Managerial Instruments in Maintenance
The important function of job planning is not given adequate importance. Thismeans that in many cases unplanned maintenance prevails instead of planned.Spare parts management is neglected. Records on the number and type of parts instock are rarely kept, making it impossible to control inventory.
Servicing and inspections are done only halfheartedly. Often there is a completelack of records on breakdowns or weak point analyses and repair. The work ordersystem is very inefficient and incomplete. Usually it is slow and nontransparent
Many of the weaknesses mentioned can be attributed to the fad that maintenance isnot adequately supported by data processing. There are - if any - many separatesystems as group-constrained solutions and no unique strategy for maintenancemanagement.
A survey of 25 industrial enterprises recently carried out by the Institute forEconomic and Management Sciences confirms these brief descriptions of thecurrent situation.
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6. INCREASING COMPLEXITY OF MAINTENANCE SERVICES
The ever-higher qualifications demanded of maintenance personnel become veryobvious when one remembers that some twenty years ago it was rather mechanicaland trade skills, which were required. Today, electronic specialists and softwareexperts play an increasingly important role.
In addition to extensive technical expertise, maintenance personnel are required tohave the ability to penetrate complex process sequences systematically. Thismeans that maintenance crews have to be able to think and act in aninterdisciplinary manner. This trend is clearly evident in the qualifications demandedof maintenance personnel servicing machine tools, shown in following total.
Qualifications Demanded of Maintenance Personnel
Servicing Machine Tools
Area of Specialization: Knowledge Required of:
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MechanicalMachine Tool Components and OperatingElements Geometry and Dimensions of theMachine ToolsSet-Up and Servicing of Machine ComponentsHydraulic and Pneumatic components
Electrical
Electrical Components and Control ElementsElectronic Components and Circuits
ElectricalMeasurement and
Control Units
Logic
Electrical, Electronic, and Fluid ControlElementsLogic Functions
Contact, Measurement and Control
Units
ControlEngineering
Basic Principles of ControlMeasuring Devices and TransducersTransformers
Principles of a Machine Tool Control SystemGeneral NC Control Systems
Programming
Principles of NC ProgrammingTroubleshooting and Recognition ofProgramming
Errors
TroubleshootingTheory of Fault-FindingLogic SystemsPractical Troubleshooting
Organization ofRepairs
Documentation of Planned and UnplannedRepairs
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Updating of FaultDocumentation
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7. MAINTENANCE STRATEGY
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7.1 Increasingly Stringent Safety Requirements
Increasing public sensitivity reinforces this criterion above all. Accidents in atomicreactors, chemical plants, and in airline travel have alarmed wide circles of thepopulation.
Maintenance experts know that maintenance, no matter how well executed andorganized cannot entirely preclude the sudden occurrence of damage.
However, there is no question that equipment weak points will be tracked downeven more efficiently in the future, through ultra sensitive servicing and inspectiondevices/systems.
7.2 Stricter Environmental Regulations
To satisfy legal requirements, many industries have found it necessary to installenvironmentally-friendly plants or plant components.
Reference need only be made to:
Coal-fired power stations - flue-gas desulphurizationSteel mills - filter plantsPaper and chem. Industry - waste water purification plants
The plant operators are thereby confronted with technologies, which are new tothem, and which also place special demands on the respective maintenancedepartment(s).
7.3 Maintenance-Oriented Design
Maintenance personnel have long called for a design process, which takes theneeds of, and for maintenance into consideration. Increasingly, their demand that"maintenance start with the design" is being put into action. One could fill entirelibraries with examples of unacceptable designs, which resulted in time-consumingand expensive repairs.
It has become widely accepted that the designer requires more than acomprehensive training. More and more, there is awareness that plant parts orcomponents may fail due to the negative impact of dirt, excessive cold or heat, peak
loads, operating errors, and/or the complexity of the plant as a whole or of thesystem on the plant part being designed.
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7.4 Relative Increase in Knowledge
Assuming the knowledge in the year 1800 to be 100 percent, its current level isapproximately 1600 percent and will presumably quadruple within the next twentyyears ff present trends continue. Innovations appear regularly and must be used ifan optimum is to be maintained.
7.5 Shrinkage of Time - Intervals
The volume of new knowledge within a given time frame is increasing at the samerate as progress is accelerating. The result is that patents, system designs, etc.within a specific field follow one another at shorter intervals.
7.6 Shorter Util ization Time of Systems, Processes and Programs
Systems, processes and programs consist of a multitude of single components,
which are modified or replaced by others as a function of the increase in knowledge.This frequently leads to a redesign of systems, processes, and programs, at ever-shorter intervals, thereby significantly reducing the effective lives of such systems.Up until now, it was estimated that a system, which was not updated regularly, hadan effective life of about ten years, but in the meantime one has to accept that it isconsiderably shorter.
Another consequence of this for system, process, and program development is thatthe conventional learning processes associated with development can now be atbest only partly oriented towards the actual situation. The learning processes mustrun concurrently to system develop it and must be directed towards a targetperformance from which one can rear to useful parts of the actual situation. Overall,the actual condition is generally so obsolete already that it no longer represents a
useful foundation on which to build.
7.7 Shorter Innovation Period
The time, which passes before a new invention can be put to practical, use (readyfor the market) is decreasing. If one traces the history of technology, one discoversthat the innovation period in earlier eras was quite long and that there wereinventions, which were not innovated at all, although they were actually practicalfrom a modem point of view.
Other inventions were developed twice, because at the time they were firstconceived, no one knew or devoted much thought to where and how they could be
profitably utilized.
When new systems are developed, it is advisable to consider not only the alreadyfamiliar possibilities, but also those, which are currently being developed oranticipated. If this is not done, then a system might already be obsolete by the timeit is implemented.
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7.8 Manifold Combinations Possible
Innovations of every type, be they technical, organizational, or other systems,consist of elements or groups of elements which have significance extendingbeyond the original purpose or field of knowledge. The choices and conceivablealterative increase exponentially as the level of knowledge and achievements rises.
The number of system components, which have to be taken into consideration fornew designs, reorganization, and/or adjustments, is constantly rising.
In practice, this means that there is not only a need for specialists who complementeach other and cooperate closely on developments, but that suitable systemtechniques must be applied in order to choose the most appropriate from the varietyof options available.
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8. What is Inspection (Condit ion Monitoring)?
Inspection or condition monitoring is a method of obtaining information regarding the
condition of machinery and is defined as "A series of activities to assure the most effective
use of the equipment during its life cycle".
A condition-monitoring program includes:
1. Planning
2. Performing
3. Obtaining measuring results
4. Analysis of results
5. Taking corrective action
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9. The Significance of the Application of Inspection Systems
Inspection should help the maintenance personnel examine machinery, (plant)
equipment. Condition monitoring is a concept, which involves the routine
organization of machine parameter values. These parameters are related to the
mechanical and operational condition of the machine.
To obtain such parameter values, technically high-developed measuring systems
are needed.
The information obtained by such inspection equipments can then be used as a
basis for necessary maintenance decisions. Such a maintenance decision could be
a planned shutdown at a suitable time, which in any case is more efficient than an
unforeseen breakdown.
As a result, many industries are now using predictive maintenance programs to
provide a guidance as to when maintenance should be performed, rather than
relying on fixed calendar dates (see the following example).
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10. Reasons for machinery failure
To build up a monitoring program it is essential to know the possible reasons of
machinery breakdown.
Possible reasons are:
- Natural wear
- Wrong operation (human error)
- Change of production (other products)
- Change of process parameters (temperature, pressure, flow etc.)
- Wrong design (manufacturers faults)
- External influence (damage from outside)
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11. TOTAL COST OF MAINTENANCE
The opinion that maintenance costs are comprised of personnel and material expenditures ha
in production shops became cost-conscious.
Maintenance Expenditures
(fix & variable)Costs of Breakdowns
Consequential costs
of Breakdowns
Personnel
Material, Spares
Energy
Tools
Rents
Education
Contractors
Product Volume
Delays
Lack of Quality
Process Energy
Sales Loss
Delayed Delivery
Delayed Income
Loss of Image
Loss of Customer
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Cost / Prod. Unit Cost / Min. ?
It's important to continuously control maintenance costs and to help keep the total cost ofpurpose, two significant values should be available in each production plant.
Maintenance Costs / Produced Unit
Cost of Loss of Production / Minute of Breakdown
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12. Maintenance Activities
Item Unit Description Operational Measures Pe
1 Motor Protection Switch Clean, check contacts and mechanical
function, check nominal current
adjustment
1 x ann
2 Miniature Breaker Clean, search for defects, check
mechanical function
1 x ann
3 Clean, search for defects, check
mechanical function
1 x ann
4 Discrepancy Control Switch Clean, search for defects, check
mechanical function
1 x ann
5 Miniature Control Switch Clean, search for defects, check
mechanical function
1 x ann
6 Pushbutton Clean, search for defects, check
mechanical function
1 x ann
7 Limit Switch Clean, search for defects
Check mechanical functionCheck contacts and function
Check oillevel and sealing
Lubricate bearings as required
2 6 x
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Check drive for abrasion
8 Spindle Limit Switch Clean, search for defects and abrasion
at drive, drive chain and contacts,
check tightness of locknuts, check oil
level and sealing
6 x mon
9 Centrifugal Switch Clean, search for defects, test contacts
and mechanical function
6 x mon
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Item Unit Description Operational Measures Pe
10 Power Contactors Clean, search for defects, check
contacts, contact pressure and
mechanical function, lubricate bearing
as required
Size:
0 1
2 3
4 10
12 14
1 x ann
11 Auxiliary Contactors Clean, search for defects, check
mechanical function
1 x ann
12 Time Relay Clean, search for defects
Check adjusted values
Check mechanical function and move
ability of gear
Check electronic circuit
2 x ann
13 Timer Clean, search for defects, check
mechanical function
2 x ann
14 Fuse Isolator Clean, search for defects 2 x ann
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Lubricate contacts with contact grease
if required, Check engage of pawl
15 Thermal Release (Over Current Relay) Clean, search for defects, check
nominal current
2 x ann
16 Thermostat Clean, search for defects
Check electrical function
2 x ann
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Item Unit Description Operational Measures Pe
17 Buchholz - Relay Test indication and release function\
Auxiliary means: Air pump
2 x ann
18 Measuring Instruments Clean, check for damages, Zero-point
and span adjustment
1 x ann
19 Optical-And Acoustic-Alarms Clean, search for defects
Check electrical function
1 x ann
20 Capacitors And Choke Coils Capacitor:
Clean and check for visual faults,
check discharging resistance
Auxiliary means: Ohm meter
Choke Coil:
Clean and visual check for faults
1 x ann
21 DC - Machines Clean Housing
Clean inside and insulation plates,
check length of brushes, change
brushes if minimal length has been
reached, check brushes for move
ability in the holders, check springs for
Weekly
2 x wee
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tension and mech.
faults, check connection wires for
tightness and for colour changes
through heat, check commutator for
visual defects
Bearings: Check oil-level at motor- Daily
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Item Unit Description Operational Measures Pe
21 bearings, check function oflubrication-ring, check roller bearing
Check bearing temperature and noise
under load
Motor cooling fan: Clean air filter and
fan blades
DC-Motor:
Remove covers, clean the windings
and interiors, search for faults, check
functions
Speedometer: Search for any oil film, if
necessary clean and change packing
rings, check length of brushes andchange if required, check move ability
of brushes in the holders
Daily
1 x ann
1 x ann
Monthly
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22 Slip Ring Induction Motors Clean housing and air-inlet, searchfor faults
Check tightness and seals of protection
covers
Monthly
Weekly
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Item Unit Description Operational Measures Pe
22 Slip Ring Induction Motors Clean Inside Housing
Search for possible faults in
connection cables, at brush holders,
Check length of brushes and contact
pressure of brushes
Change brushes if necessary
Check bearing temperature and noise
under load, Lubricate if necessary
Monthly
Monthly
Daily
23 Squirrel Cage Induction Motor Clean housing and air inlet, search for
possible faults
Check tightness and seals of protection
covers
Check bearing temperature and noise
under load, lubricate if necessary
Monthly
Weekly
Daily
24 Eldro-Brake Clean housing, search for possible Monthly
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defects, check oil level and seals
Add oil if requested
25 Accumulators Clean and check for possible defects
Check acid or alkalide weight
Weekly
Monthly
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Item Unit Description Operational Measures Pe
25 Accumulators Clean, tighten and lubricate the
connections
Auxiliary means: Personal protection
equipment (gloves, safety glasses,
protection dress),
Acid meter
Alcalide meter
Distilled water
Vaseline grease
Monthly
26 Plate-Resistors Search for possible faults
Clean and search for faulty or
deformed plates. Check for loose
connections and for loose fix bolts also,
measure plate and insulation
resistance
Auxiliary means: Ohmmeter
Every tw
27 Potentiometer, Sliding Resistance Clean and search for faults
Check for abrasion at slider and
resistor
Every tw
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Check sliding pressure of slider
28 Control Magnet Clean and search for possible defects
Check move ability and clearance of
piston rod
Check seals and mechanical function
Every
month
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Item Unit Description Operational Measures Pe
29 Brake Lifting Magnet Clean and search for possible defects
Measure protection-resistance
Auxiliary means: Ohmmeter
Monthly
30 Magnetic Device Clean and search for possible defects
Check oil-level and seals
Check for defects at the cabledrum,
Testing the function
Search for faults at slipring, brushes
and brushholders, check length of
brushes, replace if minimum length
Is reached, check contact pressure
Check cable and plug-sockets
connection for faults
Monthly
31 Load Lift-Magnet Check for faults, check connection and
sockets
Check abrasion of chain
Check if fixing bolts are tight and
covers are tidy
Visual check of cable
Monthly
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32 Power Transformer (Oil Cooled Type) Secure workplace as required
Clean transformer area
Clean transformer insulators, capacitor
batteries
Check discharge resistance of
capacitors
Every tw
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Item Unit Description Operational Measures Pe
32 Power Transformer (Oil Cooled Type) Check Buchholz relays and protection
devices
Take oil sample fro high tension test
Auxiliary means: Ohmmeter, air pump,
clean sample glass, oil test device
Every tw
33 Control Board Clean and search for possible defects
or faults, check mechanical and
electrical function
Monthly
34 Push Button Panel Clean and search for possible defects
or faults, check mechanical and
electrical function
Monthly
35 Connection Box, Distribution Board Clean and search for possible defects
or faults, check seals and tightness of
housing
Check interior housing, connectors for
defects and tightness
Every tw
36 Starting Switch (Oil Type) Clean and search for possible defects
Check seals and tightness of housings
Monthly
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Check oil level
Check abrasion of sliding contacts
Check mechanical function
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Item Unit Description Operational Measures Pe
37 Power Sockets Clean and check for any defects
Check interlocking
Every
month
38 Lighting Sockets Check for defects Every
month
39 Emergency Lighting Check for defects
Test function of batteries
Every tw
40 Lighting System Check for defects and faults
Check function
Every
month
41 Field Control Switch Clean and search for possible defects
Check drive contacts and sliders for
abrasion
Check length of brushes and change if
necessary
Every
month
42 Cabledrum (Springoperated) Search for defects, check functions
Check sliprings, brushes and brush
holders
Check cable and connection socket
Every tw
43 Crane Track Check fro defects at bus-bars, joints,
extension joints, insulators and
Monthly
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connectors
44 Crane Trolley Search for possible defects, check
tightness and seals of protection
covers
Distribution boards: Clean housing
Monthly
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Item Unit Description Operational Measures Pe
44 Trolley and interior, search for any possible
defects
Limit Switches: Clean and search for
possible faults
Check mechanic and electric function
Supply cable: Check cable car, cable
holder and rail
Check for defects at bus bar, joints,
extension joints, insulators and
connectors
Current collector: Clean insulators,
search for defects, check brushes and
spring pressure
Check tension champ of cable fixing
Every tw
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45 Emergency Diesel Generator Check electrical function by test run Weekly
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Item Unit Description Operational
Measures
Period Qualification
46 Brush-Lifting-Device Clean and search for
defects or abrasion
Lubricate as required
Check mechanical
function
Every three
month
Electrical
Technician
47 Current Collector Check contact
pressure, lubricate joint
as required
Clean insulators, check
brushes for any defects
Check pulley for
defects or abrasion
Monthly Electrical
Technician
48 Welding Converter Clean housing and
interior, search for any
possible defects, check
length and contact
pressure of brushes,
check free movement
of carbon-brushes in
the brush holders,
Search fro possible
defects at commutator,
cables, plug and
sockets
Check mechanical
function
Every two
month
Electrical
Technician
49 Welding Transformer Clean housing and
interior, check cable,
plugs and sockets for
any possible defects
Control device: Search
for faults, check
mechanical function
Every two
month
Electrical
Technician
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