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Requirement For Hydrogen (Pressurised) Gas Storage Blowdown

hydrogen blowdown storage

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#1 panagiotis_e


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Posted 30 November 2023 - 09:59 AM

Good afternoon everyone,


I would like your input on the following issue:


For a project I am working on, involving production of green hydrogen, we have also pressurised storage tanks in our scope, meant to ensure constant product output to the client, in case e.g. of electricity availability issues.


Said tanks are pressurised, NON-cryogenic. Hydrogen is stored as a gas, at 35 barg and 40 oC.


At the moment, I am designing the flare system of the plant, and I am trying to define all relevant relief and blowdown cases.


My question is the following: Apart from dedicated PRVs for relief cases, do we also need to provide depressurisation (blowdown) capabilities?


According to API 521, 7th edition, section 4.6.4, "depressurization is often considered for large process equipment operating at a gauge pressure of 1700kpa" (i.e. 17barg).



I believe that in my case, the storage tank is, technically speaking a process equipment, i.e. not a a spare, or NNF vessel, as it will frequently have to supply hydrogen to the main exporting line, to the client (and then subsequently re-filled).


As such, I would argue that depressurisation is applicable, in case of leakage (due to rupture) or a jet fire scenario (pool fire not being applicable for hydrogen system).


What is your opinon on the above? Are there any other standards or guidelines as to whether depressurisation capabilities are or are NOT required? Any other advice?


Thank you very much!


Kind regards,




#2 latexman


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Posted 30 November 2023 - 10:10 AM

What is your opinon on the above? 


Some time in the future the H2 pressure vessels will be required to be internally inspected.  They will need to be depressurized and cleared of H2.  So, yes, depressurization capabilities (or some other method) is a must.

#3 shvet1


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Posted 01 December 2023 - 04:28 AM

I am designing the flare system of the plant


Depressuring H2 to flare, correct? Why?!!

Edited by shvet1, 01 December 2023 - 04:29 AM.

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