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Relief Valve Capacity


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#1 alokjaiswal

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Posted 26 August 2019 - 01:32 AM

There are three liquid ammonia vessel operating at pressure of 5 kg/cm2g, 2.5 kg/cm2g and 20 mmHg respectively. From the top of ammonia vessels, vapor ammonia lines are going into the Ammonia compressor at different stages. In the vapor ammonia line, relief valves are provided. The capacity of Relief valves are as below.

 

1st vessel (Operating pressure - 5 kg/cm2g)                            - 6000 SCFM Air

2nd vessel (Operating pressure - 2.5 kg/cm2g)                        - 12900 SCFM Air

3rd vessel (Operating pressure - 20 mmHg)                             - 900 GPM Water

 

My queries are.

 

1. Why the Relieving capacity mentioned in terms of SCFM of Air or GPM of Water and why not in terms of Ammonia?

2. Why the Relieving capacity of two vessels in SCFM of Air and Relieving capacity of one vessel in GPM of water? 

 

Regards

Alok



#2 breizh

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Posted 26 August 2019 - 02:09 AM

Hi Alok ,

Can you share the safety valves data sheets ?

Thanks

Breizh

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#3 AlertO

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Posted 26 August 2019 - 05:00 AM

Hi Alok

 

I wonder if they are pop test report of those PSVs. Normally we use air for vapor relief and water for liquid relief.



#4 alokjaiswal

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Posted 26 August 2019 - 05:49 AM

Thanks Breizh for sharing the information.

 

Our Plant is very old commissioned in 1974. Hence, data sheet of Safety Valves are not available.

 

I got the reply that air is for Vapor relief and water for liquid relief. But why the capacity in GPM of water when the relief valve is in vapor line.

 

Thanks

Alok



#5 breizh

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Posted 26 August 2019 - 06:07 AM

Hi ,

Even your plant is old , you should have periodic calibration /check of the PSVs based on local regulation . Check for reports within your organization .

Note : Probably relevant to do Hazop and review the scenari .

 

Good luck.

Breizh



#6 alokjaiswal

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Posted 27 August 2019 - 12:06 AM

Thanks Breizh. 

 

Periodic check of Relief valves are done and I have stated the capacity based on those reports. However, I shall still look into the datasheet if available.

 

Regards

Alok






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