good engg practise

8/13/2019 Good Engg Practise

1/14

1

1

Manufacturing Technology- II

GOOD ENGINEERING PRACTICES

S.C.Ghosh

Date: 13/01/2006

2


2/14

2

3

2. Check the seam number on the job.

( A ) BEFORE S TARTING WE LDING

1. For specific seam :Refer shop weld plan, WP S and test plan.

IMPORTANT CODE REQUIREMENT AND

PRACTICES RELATED TO WELDING

4

5. Check calibrations of weldingmachine and carry out trialwhere required.

CALIBRATIONDUE ON:

31.10.99

E7018

Supercito E 7018

3. Check identification marks of welding consumables.

4. Process Quantity (max. )SMAW 15 Electrodes

SAW/FCAW 1 Wire SpoolSAW Flux 10 KgE S SC Flux 25 Kg




3/14

3

5

( A ) BEFORE STAR TING WE LDING

6. Check cable connections and earthing.

8. Provide run - in, run - out plates for L - seams.

25 mm 25 mm

25 mm25 mm

7. Clean WEP+25 mm on either side. Remove rust , paint, oil etc.



6

11. Use SS wire brush /wire wheel for SS, Inconels , Monels and

Cupro-nickels. Do not use grinding wheels used on CS.

9. Get temperature sticks for preheat & interpass.Temperature > Preheat

< Interpass

25 mm 25 mm

BURNER

10. Check preheat at least 25 mmaway from WEP on both sides.




4/14

4

7

2. Weaving < 3 x Electrode diameter.Ensure specified bead length

( B ) WHILE WE LDING

1. Tacks and temporary cleats- Use specified electrodes and preheats- Qualified Welder- No hammering

4. SMAW Electrode left over after 4 hrs - return to stores.

3. No st ray arcing on job.



8

2. Return unused consumable to shop stores.

( C ) AFT ER WE LDING

1. Welder stamp to be stamped on seams - max. 3 feet apart.

Max. 3 feet




5/14

5

9

( A ) GENE RAL

1. Use correct shade of welding glass.

WRONG RIGHT

2. Keep your head out of welding fumes.

GOOD PRACTICES FOR WELDING

10

3. Do not direct fan air on welding arc .



6/14

6

11

4. When working in confined space ensure adequateventilation / exhaust.

CONFINED SPACE

BLOWER

WELDING


12

1. El iminate mix-up of electrode / fil ler wire / flux.

6

6

140 Gms / mt

8

8

250 Gms / mt

2. Never over weld fillets ---

- 6 CFW to 8 CFW - 78 % extra weld .

- Loss of man hours + consumable

- Distortion.



7/14

7

13

3. Give minimum root gaps for fi llet joints - 3mm gap on

6 CFW increases weld metal by 125 %.

6

6

6

6

125% WELD META L


14

5. Weld bead restart - end : return arc on crater to f ill up the craterand to avoid crater cracks - porosi ty

- restart ahead of end crater so that end crater gets melted andfilled - up.

ENDCRATE R CRACK

4. Do not give excessive reinforcements.



8/14

8

15

7. For NG - SAW and ESSC follow instructions from welding Engg.

6. Burn complete electrode - max. stub and should be 50 mm.

E7018

< 50mm

E7018

> 50mm


16

( B ) SAW

1. Use only hot flux.

2. Flux is costly - always use flux recovery units-return unused flux.

3. Re - use flux only after screening cleaning and rebaking.

4. Keep flux height 25 to 35 mm during welding.



9/14

9

17

6. Adjust travel speed before starting welding .

7. Ensure that current versus wire feed rate chart is available.

8. Use constant voltage mode for DC - SAW.

35-50 mm

5. While welding circ - seams the fil ler wire should be lagging by35-50 mm.

9. If f lux is not peeling off easily, there is a problem - solve it before

continuing.


18

NG SAW

Additional requirement

1. Ensure proper alignment of the seam and welding head.

2. Ensure that long neck grinder is available.

3. Follow proper bead sequence .

4. Ensure proper wire posit ion from side-wall.



10/14

10

19

ESSC

1. Ensure cable connections and followingWelding head wrt jobCleanliness of surfaceSmooth flow of str ip thro jawsMounting arrangement of spoolLevel of jobFlux feeding arrangement

2. Adjust the Stick- out using template..

3. Ensure all welding parameters before start of overlay .

4. Ensure the correct polarity of magnetic stir ring device.

5. Ensure correct flux height

6. Ensure proper bead overlap


20

3. End craters of S S, Inconel, Nickel, Monel overlay show crack if

current is high, arc length is longer and cleanliness i s notmaintained. Crater must be filled up.

( C ) WELD OVERLAY

1. Use only specified voltage / current / travel speed to avoid higherdilution.

4. Bead overlap must be minimum 50 %.

2. Higher dilution may result in cracking : weld with correctparameters .



11/14

11

21

5. Minimum bead length per electrode must be achieved.

SS

CS

6. Clad stripping must remove complete SS material, check with

CuSo4 solution.


22

( D ) TUB E TO TUB ES HE E T WELDS

1. Remove rust - grease from tube O.D. before insert ions.

2. Take care while tacking tube - tacks may result in poros ity.

3. Give minimum two passes. Both passes must be weldedwith fil ler wire addition.

4. Do not have common end craters for both passes - stagger

them.

5. Avoid tube edge burning or tube I.D. burn through.



12/14

12

23

( E ) PIPE # PIPE BU T T JOINT S

1. Set up should be done after cleaning I.D.weld as soon as poss ible after set up

2. Thin pipes ( up to 4mm thk ) - weld using two passes ( GTAW )-do not end both passes on same location stagger the ends.

3. Root set up must be accurate - or problem of lack of penetration( less root gap, thick root face ) - will occur.

( F ) NOZZL E # SHE L L / DJOINTS ON THICK VES S E L S

1. These are highly restrained joints - and tacks may cracks.Weld thick tacks 4 - 6 passes.

2. Ensure higher preheat ( +25 C ) on nozzle forging.

3. Do not cool from preheat temperature till half the groove

thickness is welded.


24

GOOD ENGINEERING PRACTICES FOR SS

Clean WEP + 15 mm on either side of WEP with acetone

Do not walk over the SS surface

CS/LAS consumable must not come in contact with SS

During rolling of clad plated,clean rollers to avoid dents and direct

contact of CS roller

Use only SS wire wheel/wire brush for cleaning


13/14

13

25


Do not use grinding wheel previously used used on CS/LAS

Maintain interpass temperature to avoid overheating

Do not leave welding slag after welding

All temporary attachments/run in run out plates shall be SS

During removal of temporary attachment from clad surface,ensure no

ripping of clad material

Carry out CuSO4 test after clad stripping

26


Clad stripping shall not be done by arc air gouging

Spatter on stainless steel damage protective surface oxides

Weaving


14/14

14

27


During welding of thin jobs(-15mm),take care of followings

More distortion in SS

Thermal conductivity of CS

Expansion of thermal coefficient 1.5 times of CS

WEP angle,Root gap,root face to be optimized

Pickling to remove all impurities

good engg practise

Documents