Friday, November 20, 2009

RE: [MW:3701] damage of packing material of SW valve after PWHT at site

Dear Vinayak,

 

The normal practice is to remove all packing material from valve, before pre heating, welding and PWHT operations. Once NDT of valves completed the same will be re fitted to the valves. The valve manufacturers additionally supply the packing material with valves. In case of critical lines, even the valve manufacturers are called for re packing, assembly operations. The leak tightness will be checked along with the line hydro.

 

 

Regards,

 

JIGNESH R RANA


From: Nivendkar Vinayak (Mumbai - Piping) [mailto:V.Nivendkar@ticb.com]
Sent: 20 November 2009 12:04
To: piping_valves@yahoogroups.com; materials-welding@googlegroups.com
Subject: [MW:3694] damage of packing material of SW valve after PWHT at site

 

Dear all,

 

In the piping class of alloy steel, we have SW end small bore gate, globe valves. And as per the client requirements all Alloy steel piping joints shall be PWHT after welding.

 

Now , if we performed the PWHT at site at temp. 704-760 Deg C (As per ASME B 31.3 Table 331.1.1 Requirements for heat treatments), then is there any possibility of damage to packing material which is normally graphite due to heat dissipate during PWHT.

 

What type special consideration to be taken in this case. Members are requested to give suggustions.

 

Thanks in advance..

 

Regards,

Vinayak


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