RE: [MW:10992] RE: 10941] SS316L PWHT

Hi Morkani,

 

The formula for calculating strains as per UHA -44 are as follows. Generally the strains level in a dished head (especially in the knuckle area) are more than in the shell, that's why many clients call for post forming HT in the dished heads.

 

In absence of NACE MR -0175 requirements , UHA -44 would apply   to determine the requirements of post forming HT requirements .In your case MR-0175 applies , in addition there may be some client's requirements also.

 

If you see the requirements of MR-0175, Table A-2  specifies austenitic S.S(S.S 316) shall be solution annealed, free from cold work and  has hardness less than 22 HRC.The second clause has a catch, as any dished head will be strain hardened if cold formed ( which may be applicable in  this case). Once strain hardened, then hardness could increase depending on original hardness level and degree of forming.This could be minimized only through solution anneal. However for a dished heard of thickness of 12 mm , unless properly supported there may be distortion on solution anneal.

 

As mentioned by you below and my understanding of the problem the following shall be done.

• Solution Anneal  the dished head ,as proposed below.
• Check hardness (especially in knuckle radius) following solution anneal to conform to 22 HRC max requirements.
• Check hardness on the shell (preferably on the L.S and adjacent BM, HAZ) to ensure that recorded hardness is less than 22 HRC.

I would think doing all the above would ensure complete diligence.

 

Thanks.

 

Pradip Goswami,P.Eng.IWE

Welding & Metallurgical Specialist & Consultant

Ontario,Canada.

Email-pgoswami@sympatico.ca,

 

 

 

---

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of lassaad mokrani
Sent: Thursday, May 05, 2011 5:25 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:10959] RE: 10941] SS316L PWHT

Thanks Mr. Pradip

Yes, our design code is ASME VIII Div 1. As i understood from your answer and since the two conditions indicated under UHA-44 are not rreached:

1-Design temperature (-15°C-65°C) less than 676°C as per table UHA-44

2-Strain limit is less than 10% when calculated as per cylinders fromed from plate formula

Therefore we don't need PWHT only for dish ends. Am i right???

Please confirm urgently

MOKRANI Lassaad

Project Manager

EPPM-Tunisia

lassaad.mokrani@eppm.com.tn 

00216 20 649 755

2011/5/5 pgoswami <pgoswami@quickclic.net>

Hello Mok,

MR-0175,Table A.2  specifies Environmental and materials limits for austenitic stainless steels(including S.S 316) used for any equipment or components. The requirements are:-

• be in the solution-annealed and quenched, or annealed and thermally stabilized heat-treatment condition;
• be free of cold work intended to enhance their mechanical properties; and
• have a maximum hardness of 22 HRC

NACE does not have anything mentioned on post forming strain and teat treatment.

If the design code is Sec-VIII, DIV-1, then look under table UHA-44 for "POST FABRICATION STRAIN LIMITS AND REQUIRED HEAT TREATMENT" as a function of design temperature.

I hope this would help to clear the doubts.

Thanks.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist & Consultant
Ontario,Canada.
Email-pgoswami@sympatico.ca,
pgoswami@quickclic.net

-----Original Message-----
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Mok
Sent: Wednesday, May 04, 2011 11:31 AM
To: Materials & Welding
Subject: [MW:10941] SS316L PWHT

Dear All,
We are fabricating two  vessels in SS316L (thickness 12mm) diameter 794mm each to be used as fuel gas separators. We have tried to convince our client that we don't need any PWHT for the shell, since the strain doesn't exceed 5% and that NACE MR0175 doesn' oblige that.
We decided to make the PWHT only for the dish ends.
But our client insisted to do it anyway for the whole vessels.
I need your input urgently

Best Regards,

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Meilleures salutations

Mokrani Lassaad
00216 20 649 755
http://www.linkedin.com/pub/lassaad-mokrani/16/364/907


















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