Productivity and Econony

7/27/2019 Productivity and Econony

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WELDING PRODUCTIVITY

& ECONOMY


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WELDING ECONOMY & PRODUCTIVITY

Productivity is a measure of Efficiency

Productivity = Output / Input

Productivity can be improved by improving

the capacity utilization or by elimination of

waste.

Productivity is an attitude of mind.

Waste is any unnecessary input or any

undesirable output from the system.


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Output

No* 0f Parts / components / unitsproduced per shift

Weld Metal Deposited per unit time

Weld length completed per unit time

* Here number refers to defect free / acceptable partsthat meets the specified quality requirements

Output

Input

Weld Metal Deposited / weld Length Completed

Consumables, Energy, Welder hrs, Accessories


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Productivity

Overall Plant/Shop Productivity

Welding Productivity

Labour Productivity

Welding Productivity is often affected by

Productivity of other allied processes

Productivity is directly dependent on

welding time and time taken for allied

operations


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DISTRIBUTION OF WELDING COST

70%

60%

50%40%

30%

20%10%

Cost

Preparation

Assembly

Preheating

Welding

Dressing

PWHT

Inspection


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WORK MEASUREMENT TECHNIQUES

Time Study

Work sampling

Analytical Estimation

Synthesis from Standard Data

METHOD STUDY SHOULD PRECEDE WORK

MEASUREMENT

Welding Time standards


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STANDARD TIME

Standard Time for a welding operation is the amount

of time that the qualified, properly trained and

experienced welder should be take to perform a

specific welding operation under specifiedconditions under normal performance.

OBSERVED TIME * RATING FACTOR = NORMAL TIME

NORMAL TIME + ALLOWANCES = STANDARD TIME

FATIGE ALLOWANCE, PERSONAL NEEDS AND

DELAYS.

STANDARD TIME WILL BE CALCULATED BY BREAK

DOWN OF VARIOUS ELEMENTS IN WELDING.



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ELEMENTS OF WELDING OPERATION

ARCING Note down ampere, dia and length of

electrodes used.

CLEANING - Chisel / Wire Brush / Pneumatic

chipper, No. of layers used

MANIPULATION DURING WELDING Change

electrode, adjust current, getting electrodes, moveaccessories, Remove and put on helmet, gloves, apron

etc.

MANIPULATION OF THE JOB - Turning, lifting,

clamping, declamping etc of the job.



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Example Calculation of Standard Time

Sl.No.

Description of theelement

Preparation-on Time

WeldingTime

Manipul-ation

Time

01. Collect documents

2.002. Study the Drawing 1.5

03. Connect the plug and

disconnect later

0.2

04. Switch on and Stop

later0.3

05. Adjust Current 0.2



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06. Clean Work Place 1.507. Fill up the Job Card 2.0

08. Handover completed Job Card 2.0

09. Call Crane 3.0

10. Tie and loosen the piece 1.25

11. Bring the job from a distance of20 Metres

0.9

12. Clamp the earthing cable 0.15

13. Weld 2Metres with basic coatedelectrode

14.00

14. Complete Weld Ends 0.10

15. Move to side 0.60




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16. Call Crane 3.0

17. Rig and Untie 1.25

18. Change through 180 degrees

1.0019. Weld Next side 2Metre 14.0

20. Complete the weld 0.10

21. Stamp welders Number 0.10

22. Call Crane 3.00

23. Rig and Untie 1.25

24. Take the piece away for 20

Metre distance

0.90

Total time in mins. 9.70 28.20 16.40




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ANALITICAL CALCULATION

In this method, arcing time, welding time,

requirement of welding consumables etc. or to

be estimated based on the data from

Direct Time Studies and

Welding information like are time, rate ofdeposition, current etc. normally available in

electrode manufacturers literatures and

catalogure.



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Analytically calculated times do not completelyreplace direct time studies. However, they have anumber of advantages like :-

They reduce the number of studies that must bemade.

They can be used for predicting costs, schedulesand delivery periods while estimating and quoting thefirms offer.

Analytical calculations are economical to apply for

obtaining Time Standards for a wider coverage ofoperation in the plant.

Whenever new sizes or new edge preparation etc. isbeing introduced, estimates could be made withaccuracy and consistency without waiting for the jobto be taken-up for production.

ANALITICAL CALCULATION Welding Time standards


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Analytical calculation of welding data, essentiallyinvolves first finding out general expression for the

weight of weld metal deposited for a given edge

preparation, configuration and other welding data,

using previous time study results and secondarysubstituting the numerical values (size of the joint) in

the expression to get the require data.

From the weld metal weight other welding details like

arcing time, welding time, consumables required can

be arrived at using the data obtained from time

studies and welding data hand book

ANALITICAL CALCULATION



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ARCING TIME

The arcing time per joint is the duration of time forwhich the are is struck and sustained during the

welding of the joint.

Arcing

Time

Weight of weld metal deposited per electrode

Deposition rate of electrode gms/min


The deposition rate depends on the type of electrode, size ofelectrode and the current used. It can be got from Time Studyresults or it is supplied by the electrode manufacturerthemselves (e.g.. Advani Oerlikon Welding Hand Book).

Since the size of electrodes used changes for each layer, thearcing time has to be found for each layer and added to gettotal arcing time per joint.


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WELDING TIME

The welding time can be found by multiplying thearcing time by a factor.

This factor will depend on the type of joint and natureof work can be obtained from the previous time studies

on the similar work.

Also some welding data Hand Books provides theseinformation.


Pressure Vessel fabrication 2.0-2.4

Heavy machinery fabrication 1.8-3.3Railway coach under-frame fabrication 2.5-3.3

Ship hull fabrication 1.8-2.6

Erection welding work 3.0-4.0

Type of Fabrication Factor


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CONSUMABLES REQUIRED

The weight of metal deposited by burning an electrodes is notequal to the weight of core material of the electrode.

No. of

electrodes


Wt of weld metal yield per electrode

Deposition

Efficiency or

Metal

Recovery


Weight of core wire melted

The actual weight of metal deposited per electrode (I.e.) Metal

yield depends on the deposition efficiency for the electrode andthe length of the stub thrown away after welding.



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The deposition Efficiency will be more than 100 for ironpowder electrode and less than 100 for others. If n is

deposition efficiency of the electrode, L is the length

of electrode and l is the length of throw away stub,

then metal yield per electrode.= (Core Material Wt. Per Electrode * n/100 * (L- l) / L)

CONSUMABLES REQUIRED

This analytical calculation, at the best, can onlysupplement and at any rate cannot substitute Time

Studies.

The accuracy of the results obtained by this method

largely depends on the norms got from time studies.



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Design stage

Practical ways to minimize

Welding cost and time


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Selection of Edge Preparation

Thickness

Design stage


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Improper

selection

Of edge

preparation

Results in

over welding

WRI

Design stage


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During welding

Practical ways to minimize

Welding cost and time


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Electrode Terminology

Core Wire ( Dia )Flux Coating

Stub end

ThinCoated

ThicklyCoated


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Electrode data

Diameter 3.15 mm 4 mm 5 mm 6.3 mm

Time in min 1.45 1.65 1.85 2.0

Diameter 3.15 mm 4 mm 5 mm 6.3 mm

Gms/ elect. 26 38 58 90

The above data is for electrode length of 450 mm & stub length of 50

mm

Wt. Of Weld metal deposited gm/electrode

Melting time - min /electrode


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Diameter of Electrode( mm ) Rate of DepositionGms / Average Minute

2.00 11.4

2.50 12.2

3.25 19.2

4.00 25.3

5.00 35.5

6.30 51.5

RATE OF DEPOSITION OF ELECTRODES IN

DIFFERENT DIAMETERS


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Deposition

Efficiency orMetal Recovery

Weight of weld metal

deposited per electrode

Weight of core wire

melted

Deposition efficiency lies between 80 to 100 %for General Purpose electrodes

Deposition Efficiency can be higher than 100 %

in iron Powder coated electrodes

Deposition Efficiency of Electrodes


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Sl.No

ElectrodeType

DepositionEfficiency

%

Price for1000 Pieces

Wt of metal

For 1000

Pieces

kg

Cost of weldMetal

Rs./kg

01

General

PurposeRutile 90 1112 35.3 31.50

02

Low

Hydrogen

Iron

Powder

115 1774 45 39.42

03Rutile

Iron

Powder140 2033 54.9 37.03

04Rutile

Iron

Powder210 2909 82.3 35.35

Metal costs for different electrodes


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Sl.No

ElectrodeType

Melting

Time per

Electrode

in mins.

Material

Cost of

Weld metal

Rs/kg.

Labour costof weld metal

Rs/kg.

Total cost

Of weldMetal

Rs/kg

01

General

PurposeRutile 1.90 31.50 8.24 39.74

02

Low

Hydrogen

Iron

Powder

1.70 39.42 5.80 45.22

03Rutile

Iron

Powder1.85 37.03 5.16 42.19

04Rutile

Iron

Powder2.15 35.35 4.20 39.55

Weld metal costs for different electrodes


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Elec. length 60 mm 70 mm 80 mm 90 mm 100 mm

250 mm 1.05 1.11 1.18 1.25 1.34

350 mm 1.04 1.07 1.11 1.16 1.20

450 mm 1.03 1.05 1.08 1.11 1.14

Increase(Factor) in weldmetal with stub lengths

For stub length of 50 mm factor is

1.00

95% of the original value per Kg of electrode

is lost when it becomes a scrap


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50.3044.1938.80Electrode

0.440.440.44Power

4.033.983.91Labour

34.58

0.44

3.84

Length of the Stub thrown awayCostitem

200 mm150 mm100 mm50 mm

COST PER KG.OF DEPOSITED WELD METAL IN RUPEES

(For a 5 X 450 mm Long Electrode MR 115% Cost Rs.2437 for1000 electrodes


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Selection of electrode diameter

Elect. Dia 3.15 mm 4.0 mm 5.0 mm 6.3 mm

3.15 mm 1.0 1.425 1.966 2.395

4.0 mm 0.701 1.0 1.379 1.680

5.0 mm 0.508 0.725 1.0 1.204

6.3 mm 0.417 0.595 0.820 1.0


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Electrode diameterNo.of electrode

changes

3.15 mm 364.0 mm 24

5.0 mm 14

6.3 mm 11Electrode is rutile type 450 mm long with DE 0f

Electrode changes per Kg of weld metal deposit


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Welding cost

Weld metal is 3-4 times costlier

Wire loses 97% of its value when it becomes

stub

When a weldment is rejected it is more costly as

consumable & labor cost is added

Cost of welding increases to

165 % in Horizontal Position

294 % in Overhead position

Compared to 100% in Down hand position

Rework increases the cost further

Cost


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Cost of Welding

05

65

06

25

Labour cost

Electrode cost

Power cost

Equipment cost

No. represents Paise

D t ti l dR til T 60 V j i t B tt 12C i


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24.36------36.36------Total cost permeter of joint

---

---

---0.507 m

2---Cost of

Compressor

air

0.20------0.28------Power Cost

---------0.9018 mins.---Labour andoverhead costs

for Gaugine out

the root withpneumatic

chisel

21.76

2.40

4.4No4-4-m

18 mins

4.4Nos.3.15-4mm

18 mins.

28.00

4.40

4.2 Nos3.15-3Nos62 mins.

5.10 mm3.15-8mm

55 mins.

Electrode Cost

Filling-up andsealing run

Labour cost

---------2.28---3 Nos. 3.15 mmElectrode CostRoot Run

Cost Rs.II SideI SideCost

Rs.

II SideI Side

Deep penetration electrode squareButt joint Thickness 12 mm Root

Gap 2.5 mm

Rutile Ty pe 60 V joint Butt 12

mm Plate Root Gap 2 mmCost items


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Excess root Gap increases the weld metal deposit

Thickness

Design 12 16 20 12 16 20

SV

DV

790 1340 2050

424 704 1062

840 1410 2120

502 830 1222

Root Gap 1 mm Root Gap 2 mm

Included angle - 60 deg.


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Fillet sizing with excess root gaps

Results in deposition of weld metal

WRI

Fillet sizing

Effect of root gap


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Process Productivity

1.5 - 3 kg /hr. 3 - 6 kg /hr. 4 - 8 kg /hr.

Dia 3.15-6.3 Dia 1- 1.6 Dia 3.15- 6.3

SMAW GMAW SAW

D iti Effi i f ldi


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Filler metal form

And process

Deposition

Efficiency %

SMAW electrode

457 mm 60-70

Deposition Efficiency for welding processes

FCAW process with

Solid Wire 80-90

GMAW with solid wire 90-97

SAW with solid wire

95-99


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Loss associated with Major Arc welding Process

Evaporation loss

Spatter loss

Stub loss

Loss due to bad handling

Loss due to high currents

Cut wire loss

Loss due to improper

wire feeding

SMAW GMAW SAW

A A A

A A A

A NA NA

NA A A

NA A A

A A A

A A NA


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OPERATOR FACTOR

Represents the percentage of work day spent inactual welding (ARC Time) .

Percentage of ARC Time controls the economy of

deposition of weld metal .

ARC Time varies from 10% to 50% depending upon

the type of work and handling facilities.

The average figure of moderately heavy and largefabrication work is approximately 40% of welders

working hours.

High operator factors is an indication of efficiency.

OPERATOR FACTOR


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OPERATOR FACTOR Jigs, Fixtures, Setup, Fit up are directly related to

the operator factor.

Their efficiency will have a great effect upon weldingspeed and operator comfort and safety

Changing from Vertical or Overhead to the flat

position can increase the welding speed as much as400% and increase the operator factor and welderefficiency.

The use of a helper will increase the operator factor.

Welding Method Operator factor %

Manual 5-30

Semi-automatic 10-60

Mechanized 40-90

Automatic 50-100


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REDUCING THE INPUT

Proper design of weld Joint

Proper Edge Preparation

Reduce Stub End Losses (15% to 20%)

Reduction in over welding (Number of passes)

Use of Higher deposition Electrodes

Reducing the consumables like Gas, Electrodes

filer metal etc.

Reducing the Labour and Overhead Cost

Proper Estimation

Recycling of flux

Automation levels in welding


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Automation levels in welding

Set up /assembly

Tack welding

Positioning while tacking

Welding & Positioning

Finishing

Unloading

Loading of parts

LOW Medium High

Loading of assembly

Un-Loading of assembly

M M M/c

M M/c M/c

M M M/c

M M/c M/c

M M M/c

M M M/c

M M/c M/c

M M M/cM M M/c

A t ti


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Manual Assembly using Jigs and

fixtures

Manual Tack and full welding

Semi-automatic welding Mechanized welding

Special Purpose welding Machines

Mechanized up stream and down

stream processes

Automation

Positioneering


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Positioning for assembly

When the job size is big.

Positioning for assembly and welding

Eliminates handling time

Speeds production

Eliminates the need for crane operators &

other overheadsPositioning for People

To eliminate fatigue of the operator

To improve safety of operation

Positioneering

Types of Positioners & Manipulators


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Turn Table Positioners

Tilting-Rotating Positioners

Gear Driven Positioners (135 in the horizontal plane and360in the perpendicular plane)Cradle type Positioners

Turning rolls for rolling cylindrical jobs

Head Stock and Tail stock Positioners.

Special utility Positioners

Universal balance Positioners

Welding head manipulators Typical columns and

booms

Types of Positioners & Manipulators

Special Purpose welding machines


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Special Purpose welding machines


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Production of Long seam welded Line pipes

as per API 5L


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Edge milling of Plates


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Three rollerBending of Plates


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Cylindrical correction of the Rolled

Pipe edges

Pipe welding details


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Root Welding

Inside Welding

Outside Welding

Pipe welding details


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Tack Welding the outside of thePipe by Co 2 Welding


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Inside Welding by

SAW Process


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Outside Welding by Tandem SAWProcess


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Hydrotesting of Welded Pipes


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Ultrasonic Testing of weldedPi es


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as per API 5L


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API 5L


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as per API 5L


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Tack welding ( outside by GMAW )


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Inside welding system

Outside welding and UT


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g

Expansion system


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Expansion system


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Production of spiral welded pipes


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Production of spiral welded pipes


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Thank You

Documents

Productivity and Econony