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Gas Filled Relief Load Calculation (Fire And Cold)


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#1 Ghasem.Bashiri

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Posted 06 February 2021 - 04:50 PM

For wetted area (with liquid content), API 521 has some procedure for pool fire radiation.

However for gas filled system (without expected pool fire) , it is not clear procedure to calculate or estimate to determine relief load during fire case.

For such condition there is not rule similar to wetted equipment.

Please guide me. 



#2 Bobby Strain

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Posted 06 February 2021 - 05:09 PM

Look a bit further. You should find the procedure for gas expansion. However, the vessel will rupture before relief. A relief valve does not offer protection in such circumstances.

 

Bobby


Edited by Bobby Strain, 06 February 2021 - 05:10 PM.


#3 fallah

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Posted 07 February 2021 - 12:41 AM

For wetted area (with liquid content), API 521 has some procedure for pool fire radiation.

However for gas filled system (without expected pool fire) , it is not clear procedure to calculate or estimate to determine relief load during fire case.

For such condition there is not rule similar to wetted equipment.

Please guide me. 

 

Please refer to section 4.4.13.2.4.3 of API 521 SEVENTH EDITION



#4 breizh

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Posted 07 February 2021 - 01:56 AM

Hi ,

Consider to read the doc attached , pages 7-4-14 and followings from LESER handbook . It should support your work.

Good luck

Breizh 



#5 amit9330

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Posted 13 February 2021 - 01:14 AM

Fluid: Natural Gas

Set Pressure: 49 barg

Operating Pressure : 35 barg

Operating Temperature : 45 Deg. C

Allowable Over Pressure : 20%

Vessel Exposed Area 0.4 M2

Wall Temperature : 593 Deg. C

Relieving Temperature: ???

 

I saw a lot of comment of this problem and they say T1=Tn*(P1/Pn) but I don't understand this formula and another opinion is relieving temperature will be determined by the relieving pressure cause of the saturated temperature of that pressure.

 

Please Help ME.

 

 

For wetted area (with liquid content), API 521 has some procedure for pool fire radiation.

However for gas filled system (without expected pool fire) , it is not clear procedure to calculate or estimate to determine relief load during fire case.

For such condition there is not rule similar to wetted equipment.

Please guide me. 

 

Please refer to section 4.4.13.2.4.3 of API 521 SEVENTH EDITION

 



#6 PaoloPemi

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Posted 13 February 2021 - 02:07 AM

see msg #2 (Bobby Strain)

"However, the vessel will rupture before relief. A relief valve does not offer protection in such circumstances",

 

depending from application you may consider rupture disks or depressurization systems

 

said that, you can estimate the *initial* relieving temperature (for a vessel filled with gas) in different ways, for example assuming ideal gas law

P*V = Z*R*T with constant  V (V1=V2) and  Z

P1 / T1 = P2 / T2

T2 = P2 * T1 / P1

 

for a more accurate estimate you can adopt a EOS to evaluate the fluid properties, solving for example a flash operation at specified volume...



#7 breizh

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Posted 13 February 2021 - 02:09 AM

Hi,

Take a look at the Leser's handbook page 7-4-20 .

Agree with Paolo , pay attention to express the pressure in Absolute .

Good luck 

Breizh 


Edited by breizh, 13 February 2021 - 03:05 AM.





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