PWHT near to Tempering temperature for SA350 LF2 CL 1 Flanges

[asad azmi]

Dear All,

 

Greetings.

 

As per  UOP # 3-12-5 para 4.1.i.
The tempering temperature for tempered material shall be at least 50 ºF (28 ºC)
greater than the maximum intermediate or postweld heat treatment temperature.

 

Consttuction code - ASME SEC VIII DIV 1, Flanges are SS 316L overlaid in ID and Gasket face. 

 

During review of MTC for SA 350 LF2 CL 1, Flanges Tempering Temperature observed  greater by  10  deg celcius from PWHT Temperature.

 

Details are as bleow --

 

Flanges are supplied in Quenched and Tempered condition. Tempering temperature is 630 deg celcius.

 

PWHT temperature for the vessel is  620 deg celcius( minimum).

 

Please suggest whtether this can be accepted.

 

Thanks & Regards

 

Asad Azmi

[Raghuram Bathula]

as long as PWHT temperature is lower than tempering temperature. there
will be no effect on mech properties.
since you are deviating from the contractual requirement, you need to
approach UOP with a specific deviation request. i have seen in the
past UOP approved such requests. you can even demonstrate by a
simulated test coupon. FYI, API recommends 15 °C difference (refer
Table 5 note a of API RP 582)

[vaibhav Joshi]

Dear,

Some of the reputed specification like Foster wheeler recommends the tempering temprature atleast 10 greater than PWHT temprature. In your case i there should not be any technical problem if you accept the same.As far as contract point of view you should be ready with a proof that it is satisfaying the requirement of job(Mechanical properties).

Regards,
VJ

SA 350 LF2 is prob. a ASME P1 material which calls min PWHT temprature

On Wed, Aug 3, 2011 at 2:57 PM, asad azmi <azmias...@gmail.com> wrote:

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[Ramin Kondori]

Dear Asad:

Stress relieving may be done between 590 to 620 c
tempering temp=630c
630-28=602c
So you can proceed with any temp between 590-600c
No need to prolong the soaking time...
 
The only matter of concern should be the 316 cladding
As I know 316 is susceptible to temperatures around 600c
Of course low carbon grade is less susceptible but still carbide precipitation may occur...

You have to proceed with samples following same WPS and PWHT.
Then HAZ of welds (after PWHT) shall be tested against 316L requirements.

A microscopic metallography of HAZ after PWHT is a must...!!!
(that's the sensitive spot)

In that examination, you should look for carbide precipitations that will appear as black spots... Maybe client asks for Corrosion tests...

Whatever you do, Just get your client's written approval...!!!

Regards

Ramin  Kondori

   QC/Welding Engineer 

         IWE AT 0070