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Depressurizing Calculation In Gas Filled System

gas api 521

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#1 Ghasem.Bashiri


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Posted 12 March 2021 - 10:18 AM

For fire case scenario within gas plant where we have not any liquid holdup within the system, which fire heat flux is more realistic. Some people advise jet fire with 80-100 kW/m2 as per API 521 recommendation. However, it should be checked which area is subject to jet fire which is not a simple decision.

When I consider all isolated area, using Aspen HYSYS, I reach to 1000-1200 C as fluid temperature which is not reasonable (based on my understanding). 


Next issue is cold depressurizing condition which should be decided. It is possible to consider minimum operating temperature. However, when we have some minimum average and minimum recorded temperature lower that such operating temperature decision is not simple. 


Also, within Aspen HYSYS we have several Valve equation and PV work term which can change calculation results. Some people has deviation of manual recommendation for PV work term and also I could not find a good recommendation for type of valve.


Finally, I need to know for downstream of BDV with its orifice up to where low temperature condition should be used as minimum design temperature. 

#2 Ghasem.Bashiri


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Posted 16 April 2021 - 12:52 PM

If there is some guideline please assist me.

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