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[MW:23300] Welding & pwht time difference in P-91 Material

By Materials & Welding
Pradip,
 
Delaying 14 days would be way too long. Surrounding environment, humidity, pollution level, salinity all needs to be considered. Original development and welding practices for this alloy called for immediate PWHT following welding. However over the years ,control of welding practices, e.g  using strictly H4 grade consumables for SMAW, H5 grade flux for SAW, have allowed  some flexibility to the fabricators through  deferment of PWHT  but not to the extent of 14 days.
 
If  fabrication and PWHT sequences makes it mandatory to defer  PWHT then dehydrogenation treatment is a must.Please see the extract from Alstom paper. 
 
Hardness levels of as welded Gr-91 steel would be easily 350HV or more. Leaving such components outdoor,without  performing PWHT for extended period  would aggravate the scenario, through cracking by SCC.
 
If at all the PWHT is deferred , it should not be more than 3-5 days at the most , subject to  environmental conditions as above  are deemed satisfactory.
 
Thanks.
Pradip Goswami, P.Eng,IWE
Welding & Metallurgical Engineer/Specialist
Ontario, Canada
pgoswami@quickclic.net
pradip.goswami@gmail.com
 

***************************************************************************************************************************************************************** 

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of pradip kumar Sil
Sent: Monday, May 18, 2015 6:52 AM
To: materials-welding
Subject: [MW:23297] Welding & pwht time difference in P-91 Material

 

Dear All,

Can anybody inform code reference in B-31.1 welding & pwht time diference. Client is asking for 14 days.

Is it mandatory in code

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