repair of pipe line

[Mabrouki]

during repair of pipeline the welding of new part to the old one failed and many defects observed ( specially the root undercut and lack of fusion), how avoid such things?

 

[BigInch]

Find someone that can really do welding. First qualify the welder and welding procedrues on test pieces. Let him/her weld only after successfully passing the test.

 

[Mabrouki]

BIgInch thanks for reply : the welder and welding procedure are qualified and tested.
We observe during welding that the fusion of base metal (old material side) is going faster than the new material, it seem that the characteristic (weld-ability ) of old material changed
- pipe line 6"
- material A106 Grb
- Service : crude oil with height level of water cut and pipeline in service since 10 years.

 

[LittleInch]

Have a look at the material certificates of the "old" pipeline. If it's only 10 years old you should be able to find them.

If in doubt try to find a section you can test - you might have got some pipe which is not supplied to specification - either new pipe or old pipe. Forging of certificates happens.

If the pipe is empty why didn't you radiograph the weld?

If it's a tie in weld then UT or RT should spot some of these issues before you pressurize the pipe.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BigInch]

Hard to believe you're having a material quality issue with GrB pipe. It's Grade B! If procedure is qualified, then more likely it is a welder's quality issue, at least until proven otherwise. Change welders and see if it doesn't get better.

 

[LittleInch]

Only if it really is grade b.....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[brimmer]

You might try a spark test on site and see what you get there for material, check carbon equivalent, seems a bit odd.

 

[LittleInch]

If you're getting arc movement have you got a magnetic issue. You might need to de Gauss the existing pipe.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Mabrouki]

thanks guys we get better result by Gauss application to existing pipe