Welding ht-treated to non-ht treated CS in wet H2S service

[rocketscientist]

A client is asking whether he can weld heat treated ASTM 106 Grade B to non-heat treated ASTM 106 Grade B. This is > 10,000 ppm wet H2S service.

I suggested a flange-joint to preserve the treatment but he insists on welding.

How will welding affect the heat treatment?

Is there any recourse to preventing damage of the heat-treated pipe?

 

[metengr]

Not enough information. What heat treatment are you referring to for the A 106 Grade B pipe? Post weld heat treatment of original fabrication welds?

Welding will locally alter the base metal properties resulting in potentially harmful residual tensile stresses and hardened material around the weld region. This is why post weld heat treatment is necessary for specific service conditions.

Welding can be done but may require post weld heat treatment, if PWHT was the original requirement for service.

 

[SJones]

Is this question referring to use of hot finished A106 Grade B in H2S service?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[TomEun]

As metengr mentioned, the input data are not enough for the best answer. Basically you may have to confirm the followings.

- Find API RP581-2008, Table 9.3 & 9.4
- Where is the spec break? Is the joint belonging to wet sour or non-wet sour?
- pH in the service?
- Hardness on base metal and new HAZs by welding?
- The client’s spec requirements.

The most critical requirement for seamless pipe weld in wet sour service is the hardness. So when the hardness on HAZ is below 200 BHN without PWHT, it may be acceptable unless there are some remarkable issues from the above confirmation.

Thomas Eun

 

[0707]

In H2S service the seam weld between heat treated ASTM 106 Grade B to non-heat treated ASTM 106 Grade B must be PWHT.

LM

 

[SJones]

Why must it?


Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[0707]

TO RELIVE STRESSES CAUSED BY THE WELD PROCESS TO AVOID SSC.

LM

 

[SJones]

And does ISO 15156 mandate this stress relieving?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[0707]

I supose NACE MR 0175 does recommend it.

 

[SJones]

Maybe try reading it!

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04