Are pressure drop calculations required for a PSV if there are no credible overpressure scenarios? If so, how should the properties of the fluid be determined for the pressure drop as there is no relieving pressure, temperature, or state?
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No Overpressure Scenario P Drop Calcs
#1
Posted 04 May 2017 - 08:03 AM
#2
Posted 04 May 2017 - 08:29 AM
ASME Code Case 2211 (October 1999) lists conditions where, if applicable, a PSV would not be required. A lot of engineers, myself included, consider these Code Case 2211 requirements so onerous that it is more economical and expedient to just put a small PSV on the pressure vessel.
A PRD Record without inlet and outlet pressure drop calculations is incomplete.
I recommend you get creative. Use air, nitrogen, or steam; something convenient. Make the faux scenario fit in the smallest Code PSV you can buy.
#3
Posted 04 May 2017 - 08:51 AM
It seems you can dispense with the calculations along with the PSV. But you give no information.
Bobby
Edited by Bobby Strain, 04 May 2017 - 08:51 AM.
#4
Posted 04 May 2017 - 09:30 AM
ASME code (latest edition) tries very hard to make is so that a PSV is required regardless of the situation. Some of the documentation required is almost impossible to obtain (for example, "The user shall request that the manufacturer's data report state that overpressure protection is provided by system design"). Not many manufacturers will actually agree to this.
It is a tank ~50% full of liquid Cl2 with an existing PSV to a scrubber header.
#5
Posted 04 May 2017 - 09:44 AM
For the existing PSV, inlet pipe and fittings, and outlet pipe and fittings, use sat'd Cl2 vapor at 10% overpressure or accumulation (process upset scenario) and calculate the inlet and outlet pressure drop. Done.
#6
Posted 04 May 2017 - 01:11 PM
You don't mention how you fill the vessel. Maybe you can overpressure from the filling source. Then you will relieve liquid. So, look around. Are there flammable materials nearby?
Bobby
#7
Posted 04 May 2017 - 02:28 PM
A P&ID would help us help you.
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