"HEATING WELDS AFTER TEST" GOOD OR BAD PRACTICE AT CONSTRUCTION INDUSTRY ?

All your answers can be

Heating after welding is as you guess a bad practce - If I understand what you are saying. You are trying to align the pipes by heating the pipes/ welds and bending - you are keeping a lot of un relieved stresses in a pipe. I don;t think codes (Mr Galala is the expert on these) can tell. But at our works what ever little welding we do on hydraulic lines or in Gas turbines, , it is a strict no - after all the processing is done.

All the alignments and other aspects are taken care of during fit-up and necessary fixtures and precautions are taken to avoid distortion during welding. I don't remember having to resort to this.

And the amount of repair you are doing is called a major repair by any standard - removing 50% of weld thickness and re-depositing.

The pipe line must be re-subjected to all the treatments and NDTs after repair.

Assume a pipeline has failed in X-Ray - what is the procedure ? As you know, these are done (usually) before PWHT- that means the PWHT is carried out in the ASME vessels after all the major repairs are carried out.

The repair is repair - it is not that who has supplied material or labour or other infrastructure. And in case of repair, all the activities have to be duplicated.

(In fact in certain pipings we carry out the NDT twics - the MPI/LPI is repeated after PWHT to ensure no SR cracks have crept in- and we have seen in a few rare cases the joint failing in second MPI)

Depending on the depth then we either remove the defect and leave as it is or repair and depending on the depth/ code etc carry out the PWHT again and re-subject to the NDT.

After the long monologue- my opinion is and as per our internal standards are: all the (mal) practices mentioned by you are not acceptable practices.

One point you must keep in mind is from the B31.3 code:

300 GENERAL STATEMENTS

(2) This Code is not intended to apply to the operation,
examination, inspection, testing, maintenance, or
repair of piping that has been placed in service. The
provisions of this Code may optionally be applied for
those purposes, although other considerations may also

be necessary.

Now this is where things get confusing - repairs to already accredited B31.3 piping fall under you local jurisdictional rules and your company's QA/QC program for pressure piping (which usually refer back to B31.3 for repairs with some qualifications)

You may also look to API 570 (which may also be referred to by your jurisdiction) which, ironically states:

8.1 REPAIRS AND ALTERATIONS

The principles of ASME B31.3 or the code to which the piping system was built shall be followed.

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In the end - you should repair the pipe with B31.3 in mind - with additional considerations (and always follow your company Pressure Program):

• Must follow original welding procedure
• Should NDE all repairs (regardless of lot size specified by B31.3) including RT and MPI/LPI
• Must follow original heat treatment procedures
• Please confirm that you have indeed performed postweld heat treatment on the original A53 material, according to B31.3, Section 331 & Table 331.1.1
• Regarding 304l & 316l SS - B31.3 states that no heat treatment is required, regardless of thickness (which is appropriate for metallurgical issues) NOTE: heat treating austenitic stainless is usually avoided to ensure you don't sensitize the material and reduce the corrosion resistance.
• It would be prudent to perform a hydrotest again - using hydro pigs/plugs would be appropriate if necessary.

To specifically answer your questions:

1. Yes - consider it a repair
2. No - must perform NDE
3. Yes - generally bad practice because it shouldn't be necessary in the first place and opens up the "Piping Repair" QA/QC, heat treatment issues
4. YES - Weld defects (particularly cracks)
5. API 570 (ASME PCC-2 which covers other issues, not necessarily your situation)