Sunday, May 23, 2010
Anyone can tell me what will be the set pressure for the spare PSV in the multiple PSV (3 X 50%) arrangement. ? Set pressure for 1st PSV is preset at 100% whilst set pressure for 2nd PSV is 105% of 1st PSV set pressure. Should we set 3rd PSV (spare) at 100% or 105% of 1st PSV set pressure ???
Considering a PSV systems with
- PSV-1 set at 100% set pressure
- PSV-2 set at 105% set pressure
- PSV-3 is spare for PSV-1 or PSV-2.
IF PSV-3 set at 100% set pressure
i) whenever PSV-1 is removed for inspection / maintenance, PSV-3 will be put in service. Then the situation will be - PSV-1 out of service
- PSV-2 set at 105% set pressure
- PSV-3 set at 100% set pressure
ii) whenever PSV-2 is removed for inspection / maintenance, PSV-3 will be put in service. Then the situation will be
- PSV-1 set at 100% set pressure
- PSV-2 out of service
- PSV-3 set at 100% set pressure
IF PSV-3 set at 105% set pressure
i) whenever PSV-1 is removed for inspection / maintenance, PSV-3 will be put in service. Then the situation will be- PSV-1 out of service
- PSV-2 set at 105% set pressure
- PSV-3 set at 105% set pressure
ii) whenever PSV-2 is removed for inspection / maintenance, PSV-3 will be put in service. Then the situation will be
- PSV-1 set at 100% set pressure
- PSV-2 out of service
- PSV-3 set at 105% set pressure
Recommended :
Subscribes to FREE Hydrocarbon Processing
RECOMMENDATION
Therefore setting spare PSV other than 100% of set pressure will possibly lead to situation where the initial relieving pressure higher than 100% of set pressure. This is against code requirement and therefore the spare PSV is recommended set at 100% of set pressure.
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Labels: Overpressure Protection, Pressure Relief Device
3 Comments:
General practice is to have a rupture disc backing up a PSV, particularly when viscious non Newtonian fluids are involved..........gary prager
Dear Joe Hello/Good Morning,
Although bit delayed (almost a week over) response.
Just a wild thought If PSV#1 is set 100% and PSV#2is 103% and PSV#3 at 105%.
Does that leads to an acceptable scenario;Probably trial worthy.
Regards
SMWA
@Gary,
Thanks.
@SMWA,
Thanks for your participation...
PSV-1 set at 100% set pressure
PSV-2 set at 103% set pressure
PSV-3 is spare for PSV-1 or PSV-2 set at 105% set pressure.
If PSV-1 out for service, remains
PSV-2 at 103% set pressure
PSV-3 at 105% set pressure
This is not acceptable as relieving pressure is exceeded 100% of set pressure.
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