Distortion in SS pipe welding

[Saurabh Mishra]

We are doing pipe to pipe welding of A358 material ( Dia DN250 and thickness is 9.53)

In that we are facing distortion problem. To control the same we have tried various process and technique as below.

1. First Welding- We did welding with GTAW process and observed the diametrical distortion approx. 4 to 6 mm.

2. Second Mock up- We change the welding process from GTAW to GTAW+SMAW with restricted root gap 2mm follwed by cleat in four location of seam. And also we did welding opposite segment one by one. In which we observed distortion upto 2 mm except one local portion 3mm.

3.  Third mock up- We followed the same process except welding sequence. This time we completed welding using back step method and found same result as in second mock up.

For both second and third mock-up we strictly maintain inter pass temperature. 

Now can anyone guide weather 3 mm distortion is acceptable?

if yes then please reply with on what basis it can be accepted.

and if not then what method can we try further to control distortion to bring it in acceptable limit.

Thanks/Regards

Saurabh Mishra

[M.Nagoor Meeran]

Dear Mishra

 

Pl refers your contract documents for acceptance. However we can control the distortion by using following method,

—  Minimum welding current as per WPS.

—  Intermittent welding

—  Do not over weld

—  Design welds location near the neutral axis.

—  Balance the weld around the neutral axis

—  Sequence welding

—  Pre bending OR  Pre cambering

—  Back to back clamping

—  Double operator welding technique

—  Keep the angle of weld joint to the barest minimum.

—  Minimize No of passes using  larger size of electrodes  

 

TR

Meeran

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