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Requirement For Bleed At Psv Outlet


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#1 SawsanAli311

SawsanAli311

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Posted 04 December 2018 - 01:31 PM

Dear All, 

 

For all pressure safety valves provided with inlet isolation valves, it is conventionally required to have a bleed between the inlet isolation valve and the PSV to ensure adequate depressuring before removing the PSV for service. 

API 520 PII also specifies the requirement of a bleed between the PSV and the outlet isolation valve stating that it can be required to depressure the portion between the PSV and a closed valve outlet. 

 

However, considering that the outlet isolation vlave is always locked open during normal operation and that it will only be closed with the PSV is removed for inspection/maintenance following the careful administrative interlocking procedures, do you really think that a bleed vent valve is still required between the PSV and the OUTLET isolation valve?

 

Thanks 



#2 fallah

fallah

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Posted 04 December 2018 - 02:40 PM

 

However, considering that the outlet isolation vlave is always locked open during normal operation and that it will only be closed with the PSV is removed for inspection/maintenance following the careful administrative interlocking procedures, do you really think that a bleed vent valve is still required between the PSV and the OUTLET isolation valve?

 

 

Hi,

 

Although the outlet isolation valves in most PSV arrangements are in CSO position, bleed vent/drain valve is required in-between to vent/drain the trapped fluid before removing the PSV for maintenance, inspection,...






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