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Fire Case For Sizing Of The Psv Installed On The Vessel

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#1 vaibhav


    Junior Member

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  • 26 posts

Posted 24 April 2019 - 12:06 AM

Dear Members I am working on the project of jet fuel transfer pipeline project to airport .For doing jet fuel filter, micronic filter and filter water separator vessels are installed in the system with safety valve installed at the top of the vessel. This valve is designed for thermal relief case only. vessel capacity is 400 m3 / hr and size is 1 meter ID & HEIGHT is 1.8 Meter. vessel operating and design pressure is 45 bar g & 65 bar g respectively. vessel operating and design temperature is 50 Deg C & 90 Deg C respectively. consultant had given the following comments - The credible fire scenario as per API 521 , For the liquid filled vessels is external fire case . Fire exposure on equipment can result in overpressure due to vapor generation and fluid expansion. Fire exposure can also cause overheating of the vessel walls resulting in a reduction in material strength. Therefore currently filter vessels are not protected against the external fire case. pl. clarify. I need forum members advice in order to close this comment. do we really need to consider external fire case scenario for sizing of the PSV on the vessel at all the time ? vessel is use for the filtering jet fuel product having density range from 800 - 840 kg / m3. how the overpressure in the vessels is expected to be handle in the external fire event ? please advise. regards vaibhav

#2 Chemitofreak


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Posted 24 April 2019 - 01:54 AM

Hi Vaibhav,


Part A:


In our company the criteria for excluding fire case is as follows


1) If the volume of liquid handled in the vessel is less than 500 Liters


2) The fluid in the system should be non-toxic


3) Only fire is the applicable scenario


The only case when the filter is not provided with a PSV is when the volume is less. If the volume is more and the filter is located in a fire zone, definitely PSV is required. 


Part B:


Refer Clause of API 521, which states that the liquid filled vessel will be subjected to thermal expansion for limited time after which vapour generation becomes determining case.


Revert in case of any query.

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