PWHT per B31.1 2

[iam42]

Welding a F91 6000# Weldolet to a 14" Sch 160 P91 pipe requires PWHT - True or False?

 

[metengr]

Absolutely true, no exceptions to the rule. Your answer is spelled out in B31.1, Table 132.

 

[iam42]

Metengr,

thanks for your support, I have a boss who keeps arguing with me that PWHT should be calculated on weld thickness not material thickness.........this argument is more to do with welding P4 materials.

Thanks

 

[weldtek]

iam42,
I don't have a current copy of B31.1 handy, but, your boss would be right by the '92 edition.

 

[metengr]

weldtek;
Using older editions of any Code to skirt the issue regarding PWHT is not wise because Grade 91 was not endorsed by B31.1 at that time.

New materials that are used in construction must be understood as to their use. Using an excuse like an older edition of the code to skirt the issue of PWHT, especially for Grade 91 material, might work as a loop hole for some but to me this is technically unacceptable and plain irresponsible.

 

[unclesyd]

P91/T91 is an excellant material but has to treated with due diligence. There is no wiggle room, one just has to follow the rules.

I think it would be beneficial for you and your boss to read the following pdf.

http://www.psimedia.info/Industry Alert.pdf

If your are to follow the/a code it has been my understanding that if it's new construction you have to use the latest incarnation.

 

[weldtek]

Metengr,
Your comment is duly noted, however, I was not suggesting that using an out of date Code book is an acceptable practice, nor was I taking issue with your comment regarding the necessity for PWHT on P91, I was merely pointing out that, at least in the '92 ed. of B31.1, weld thickness was the governing factor for determining PWHT soak times. This is the case in other Codes such as Sec VIII, but, I find many people fail to grasp this point. Of course, Code rules are minimum requirements, and other factors may need to be considered when determining approprite soak times for PWHT.

 

[stanweld]

The nominal material thickness governs for P-No. 4 and P-No 5A materials. There are some deviations allowed for P-4 materials where weld thickness governs regarding seal welding of threaded or other mechanical joints and attachment welds for non load carrying attachments (applicable for P-5A as well). All welds in or to P-5B materials require PWHT.