Testing Setup of Emergency Vent PSV on 5000bbl Oil Tank

Mechanical / Civil engineering, Design of Pressure Vessels, Heat-exchangers, Piping, Steel / Civil Structure etc.

Testing Setup of Emergency Vent PSV on 5000bbl Oil Tank

Postby sahumayun » 06 Apr 2014, 10:16

My query is regarding 24” Emergency Vent PSV to be installed on new 5000 bbls cylindrical fixed-roof type Oil Storage Tank. As per our company practice, we counter-test the new PSV at our workshop before installation. Hence, we fabricated a special test bench for testing of received emergency vent.

Specification of Emergency Vent:
Set pressure Pressure: 2.0 oz / square inches
Maximum capacities: 742,000 scfh (air) @ 2 oz / square inches **
Make: Shand & Jurs
Size: 24” x 150#

Findings of the test conducted at our site workshop are as follows,
1. The PSV was not functional much above the given setting range (02 oz/in Sq)
2. After removing all the protection weights; it was operative on 01 PSI (16 oz/in sq), which is much higher than the required set-pressure.

We urgently need to commission the tank and this emergency vent has failed in testing. I have following queries regarding the situation here,

1. Is the fabricated test-bench fit for testing of 24” emergency vent (see attached snaps of test-bench)? Since volume is one of the key factors in designing of these emergency vents. We cannot create that volume during testing. So does this test bench can actually verify, if the set pressure is ok or not?
Vendor has provided the assurance certificate of its testing and has recommended installing it without counter-verification.

2. Can we commission the tank without emergency vent PSV? What are the risks involved? We also have a VPSV fully functional installed on the tank. [Set Pressure 1.5 oz/sq in Gauge & 0.5 Oz/ sq.in Vaccum]

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Regards, Ammar
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Re: Testing Setup of Emergency Vent PSV on 5000bbl Oil Tank

Postby tosif » 02 Jun 2014, 13:25

You can commission the tank without emergency vent PSV in presence of VPSV fully functional installed on the tank, if both have the same capacity. Also ensure that VPSV alone can handle the worst case design scenario of Pressure protection, which I believe in your case would be external fire.

Also note that mostly emergency PSV is installed as additional protection level, possibilly due to higher SIL requirement.
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