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Hysys Depressuring Utility Pressure Question
#1
Posted 15 August 2025 - 04:20 AM
#2
Posted 16 August 2025 - 09:43 AM
I question whether API 521 guidelines apply to underground hydrogen storage. If you are convinced you must depressurize within 15 minutes, then you should justify your initial pressure assumptions by calculation and documentation. Why not estimate the different sections individually with different initial pressures?
#3
Posted 19 August 2025 - 07:17 AM
In general, initial pressure for the emergency case (fire/confirmed leak) will be design pressure for the non-compressor system. And for the compressor system settle-out condition will be considered as initial condition for the depressurization.
#4
Posted 19 August 2025 - 06:10 PM
#5
Posted Yesterday, 03:35 AM
I question whether API 521 guidelines apply to underground hydrogen storage.
I concur.
cammycheme, give API STD 521 a second read.
At 4.6.6 Depressuring Rate (7th Ed.) the discussion revolves around the risk of vessel rupture engulfed in a pool fire, where it's important to lower the system pressure before a fire weakens the vessel wall. At a cursory level, that consideration is not relevant to cavern storage.
Hydrogen fires tend to lead more to jet fire risks and you'd do well to refer to Appendix A Analytical Methodology for Fire Evaluations of API STD 521 and refine your focus to the key equipment at risk - I'm thinking surface process equipment. At the very least, I'd expect that you'll reduce the scope of the depressuring system and optimise flare size.
Edited by astro, Yesterday, 03:35 AM.
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