Is PWHT necessary for C/S pipe[Hydrocarbon with > 100 PSIA partial P] 3

[Zylinderkopf]

Greetings to all:

I am re-posting this question in your forum as the AWS Forum did not have any visitors that elected to respond to it - - my error.

Our refinery has a an ASME B31.3 Pipe Specification with the particulars included below.

I can not seem to verify the reasoning behind this Specification's existing requirement for PWHT (could it possibly be some sort of H2 bake-out?).

Otherwise, maybe there should not be a PWHT requirement in this case (all pipe and appurtenances covered by this spec are P1 material).

As such, if anyone could share with me an informed judgement as to whether PWHT is / is not a valid requirement in this case then I will remain grateful.

Thank you all (again) for your time and kind consideration of my enquiry.

- - Pipe Specification Particulars - -

Material: Carbon Steel (pipe utilizes ASTM A106 Grade B CS)
Pressure / Temperature Limitations: ASME Class 600
Service: Hydrocarbon with > 100 PSIA H2 Partial Pressure
Minimum Corrosion Allowance: 0.050"

 

[metengr]

What pipe schedule and thickness is installed? Did you review ASME B31.3? Look at PWHT requirements for P-No 1 base materialin B31.3, it is thickness based.

 

[stanweld]

If the thickness is < or = 3/4", B31.3 does not require PWHT. Assuming that the thickness such that PWHT is not required, PWHT may also be required to prevent stress corrosion cracking due to the partail pressure of hydrogen. It is noted that you did not indicate the temperature of the fluid.

 

[Duwe6]

This PWHT is not for Code, B31.3 or other. It is for 'process', to reduce the chance of HIC -- Hydrogen Induced Stress Corrosion Cracking. Other processes that require PWHT are liquid ammonia and strong amines, like MEA.

 

[Zylinderkopf]

Greetings to all and thank you all for your welcomed and valuable information.

metengr:
Thank you for your valuable information. The pipe schedule and thickness would be one-the-same, I'm thinking (maybe?). If this is correct then it is a range associated with either the pipe NPS or the appurtenances (O-lets, nipples, and the like). All of the pipe schedules, in my application, would measure less than 3/4-inch, as stanweld has advised me in this post thread.

I did not review B31.3 and apologize for that. I will remember to review it again before I submit any other similar posts.

stanweld:
Thank you for your valuable information. The pipe wall thicknesses in my application would all summarily be less than 3/4-inch.

The process temperature is (+)350 deg. F. My apologies for not including that information earlier.

Duwe6:
Thank you for your valuable information. I will make a note that the named material is predisposed to HIC when subjected to the subject process conditions.