POST WELD HEAT TREATMENT

[chitessy]

Hi All,

Am writing a propose welding procedure specification for a 18" X 12.7 MM pipeline of about 1 kilometer in length using API 1104.

I will need advice if post-weld heat treatment is necessary.

Thanks All

Chitessy

 

[LittleInch]

Consult a welding engineer.

I doubt it based on the minimal data you've given us (no material info etc.), but any WPS would need proper checking and signing before use so you need to ask the welding inspector who is going to approve it.

would seem to be a pretty basic question and doesn't sound like you've read API 1104. Far better to ask questions like "section x.y.z. of API 1104 says "...." Does this apply to my case?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[weldstan]

One assumes that either B31.4 or B31.8 applies to pipeline construction; in which case, PWHT is not required. If service dictates PWHT to mitigate stress corrosion cracking, the Owner must provide the requirement.

 

[LittleInch]

Err, why / where does the use of 31.4 or 31.8 mean PWHT does not apply? I agree it's fairly rare, but this is a material / thickness /welding thing as far as I know.

E.g. 434.8.3 c) of 31.4 includes PWHT where this is called for in the WPS. I can't see anywhere it says PWHT is not required as this is under the scope of 1104.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[weldstan]

API 1104 addresses WPS, its qualification requirements, Welder qualification requirements and acceptance citeria of production welds. The design/construction Code dictates whether PWHT is required. Piping Codes ASME B31.4 and B31.8 do not require PWHT of carbon steel pipe welds for the 12.7 mm (1/2") wall pipe.

If PWHT is required by the Owner, API 1104 requires the WPS to be qualified with PWHT.

 

[LittleInch]

Ok, 434.8.9 of 31.4 does state that PWHT is required above 32mm weld throat thickness for stress relieving purposes. It is very unlikely that PWHT would be required, but the WPS is the place to decide if it is required for any other reason.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[weldstan]

Disagree. The service or potential for delayed cracking dictates the need for PWHT. Procedure qalification testing may well verify the need for PWHT.

 

[BigInch]

You're both right up to a point. I think the root of the confusion may be that the pipeline codes B31.4 and 8 are not precisely the same in this regard.

In the B31.8 gas pipeline code PWHT is required per 825.1, based on carbon equivalent (CE), which as you all know is a measure of the potential for cracking based on the material's hardness. However, per ss 825.2 this code also requires stress relief when the material thickness is greater than 1-1/4" (32mm), regardless of the material's CE value.

In the B31.4 liquid pipeline code ss 434.8.9 states a thickness for which PWHT is required for material thicknesses above 1-1/4" (32mm), but this code goes on to say "unless it can be demonstrated by WP qualification testing" that it is not necessary.

In any case, and IMO, not stress relieving any weld involving material thicknesses above 1-1/4" is definitely pushing the risk frontier for immediate cracking on cooling, or if not that, for high possibilities of longer term cracking as the result of some other mechanism. so I would stress relieve such thicknesses, code required or not.

that said, chitessy (Mechanical), what is it? Liquid or Gas Code?




I hate Windowz 8!!!!

 

[chitessy]

Is a Gas line and the material is API 5L Grade B 18" X 12.7MM

 

[BigInch]

What's the gas composition? If there is H2S, PWHT may be required.

Learn from the mistakes of others. You don't have time to make them all yourself.

 

[DekDee]

Guys,
Am I missing something here ? - it is 12.7 mm wall thickness (1/2") - why all the discussions about if the WT is over 1 1/4" (32 mm)?

IMHO weldstan has given the appropriate answer to the OP

"API 1104 addresses WPS, its qualification requirements, Welder qualification requirements and acceptance citeria of production welds. The design/construction Code dictates whether PWHT is required. Piping Codes ASME B31.4 and B31.8 do not require PWHT of carbon steel pipe welds for the 12.7 mm (1/2") wall pipe.

If PWHT is required by the Owner, API 1104 requires the WPS to be qualified with PWHT."

Regards,
DD

 

[BigInch]

Agreed that it is not usually required for wall thickness and cracking upon cooling concerns, however there are other reasons regardless of wall thickness or what says API 1104. The OP didn't say if he was using X100 pipe for example, nor did he mention the qas composition.

Learn from the mistakes of others. You don't have time to make them all yourself.

 

[racookpe1978]

I am not convinced the original poster has the knowledge, office and company support and resources, nor the background himself to set the job up or write teh contract for this pipe safely.

He/she may learn it with time and money invested, but not with what has been shown here so far. It's good he's asking questions. But, where is his boss and his engineering manager?

 

[Duwe6]

"But, where is his boss and his engineering manager?"

Maybe I'm wrong, but I've seen this happen *many* times:
​

These days, his boss is probably more attached to the $$ spreadsheet than the eng. calc's and fluid corrosion/cracking potential. His Eng. Mgr retired and has not been replaced, because youngblood hasn't made any expensive mistakes [yet], so "let the new guy run with it." He is much more Cost Effective [until there is a pricy mistake].

 

[chitessy]

Thanks All,

I have qualified a welding procedure with ISO 13847 and another procedure with ASME B31.3 together with ASME SECTION IX. I qualified the procedure, supervise all the test coupon welding, NDT and mechanical test, PQR and finally produce the final WPS which are being use for the production welding. This I did for my present place of work

So is not like I don't have knowledge in this business like racookpe1978(Nuclear) pointed out.

What Weldstan(material) said is exactly my thought after going through API 1104. But I had to post this question so as to learn from people that are more experience and professional than myself and also hear their view.

Also, is a different smaller firm that approach me to help them out with welding procedure using API 1104 and PWHT is not required by the Owner.

Once again, thanks all for the contribution, I love you all

Best Regards to you All

Chitessy

 

[racookpe1978]

Thank you for your comments.