PWHT requirment for SS 316L sour service 2

[fakhfakh]

Is it required to PWHT 316L plates as per MR 175 for sour service ?

 

[Okaman]

according to my study, it is very difficult to detect, avoid, or characterize the failure caused by sour environment, especially with the H2S contain. Even by using special steel that can withstand the hydrogen cracking, we still found the hydrogen cracking. So my suggest is to do the PWHT to eliminate the hydrogen.
correct me if i am wrong =D

 

[metengr]

According to MR0175-2003 for CRA's, if the plates are provided in a solution-annealed condition, and no cold work was performed, only welding, they can be used in service following the necessary restrictions for service conditions.

If the plates were cold formed, they should be re-solution annealed prior to service.

 

[fakhfakh]

Thank you

Rolling, is it considered cold forming ?

In addition, i've seen that the fluid inside is classified Lethal. Has this also an incidense on PWHT requirement ?

 

[metengr]

If the rolling is done below 1900 deg F as part of forming, yes, it would be considered as cold forming.

PWHT is NOT required nor prohibited for this material.

 

[Okaman]

thank you metengr

 

[fakhfakh]

Thank you

Is it the same case for cladded carbon steel with SS 316L ?

 

[fakhfakh]

It seams to be that SS316L plates are not so convenient for pressure vessels manufacturing under sour service requirments!

The solution annealing of a shell after rolling requires special facilities. Am I right ?

 

[fakhfakh]

After check in MR 175 I don't agree with you Metenger that rolling is considered as cold forming since it is not designated to enhance mechanical properties.

(see § 3.5.1)

 

[metengr]

fakhfakh;
The problem is the introduction of strain into this material from forming. It is not a matter of enhancing mechanical properties, it has to do with precipitation of carbides in-service at locations of strain from forming. This is why solution annealing is critical for these materials after forming.

 

[fakhfakh]

metengr

I still don't agree. Since SS316 accepts a very high strain and again as specified in the MR175 annealing is required only if cold forming is to enhanse mechanical proprety (to harden the steel). My be the case is applicable for dish head manufacturing

 

[metengr]

fakhfakh;
Ok, we can disagree. My final comment is look at ASME B&PV Code, Section I, PG-19. Look at what is required when % strain is introduced into the material - not for enhancement of mechanical properties but simply from forming strains. You can then decide what is right -

PG-19 COLD FORMING OF AUSTENITIC
MATERIALS8
The cold-formed areas of pressure-retaining components
manufactured of austenitic alloys shall be heat treated for
20 min per inch of thickness or for 10 min, whichever is
greater, at the temperatures given in Table PG-19 under
the following conditions:
(a) the finishing-forming temperature is below the minimum
heat-treating temperature given in Table PG-19....