Dear Subhendu Mukherjee,I have worked on LPG discharge line 3" to 10" header line to Tank and Tanker filling.In the dicharge line gate valve comes before the Check Valve(NRV).Steve is correct flap of the check valve must be capable of resisting maximum pump head .The designer some times do mistake in P& Id.I face the same prolem in which the TSV shown on P&ID and Isometrics were contradictory in locating it.However the designer confirmed that P&ID only shows the accessory not the exact location.Regards,Md Danish
Steve McKenzie <Mechproj@xtra.co.nz> wrote: Hi Subhendu Mukherjee
your P & ID is unusual. Normally the isolating valve is downstream of the check valve if there is a duty and standby pump. However the flap of the check valve must be capable of resisting maximum pump head or there is not much point in having it. Also it is increasingly unusual to see gate valves on water nowadays.
Cheers
Steve McKenzie
-----Original Message-----
From: Subhendu Mukherjee [mailto:subhendu_mukherjee2001@yahoo.com]
Sent: Friday, May 02, 2003 10:19 PM
To: piping design
Subject: [PipingDesign] Does Gate Valve comes before check valve in
discharge line
Hi friends, I faced a problem while doing layout for a pump suction (8") / discharge (6") line. P & ID showing the gate valve is placed after discharge nozzle before the check valve. This line is connected to a tank nozzle with an isolation valve. It seems to me very confusing considering at the time of back flow ( after the pump is stopped) the thrust exerts by the liquid on the check valve may cause damage to its flap. My question is does gate valve comes before check valve in discharge line at all? Or the P & Id is not correct? Your cooperation is solicitated. Regards, Subhendu
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[Non-text portions of this message have been removed] Received on Sat May 03 04:00:00 2003
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