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Relief Valve Adequacy Check


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#1 umairbhatti42

umairbhatti42

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Posted 11 May 2020 - 04:09 AM

Dear All,

 

I intend to check capacities of installed relief valves at ammonia plant. The objective is to limit operation of plant load higher than the design relieving capacities of RVs as we are operating plant at load higher than the design. Since API-520 is for sizing the RVs, however in my case, I just only need to perform a capacity check,

 

So kindly suggest which standard or method should i follow. Also, do i need to consider different scenarios in this evaluation such as fire case or non fire case, block valve case etc.

 

Looking forward for your valuable comments.

 

 



#2 breizh

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Posted 11 May 2020 - 05:04 AM

Hi,

Good to review the existing Hazop study to acknowledge the scenari prior to perform the check.

Good luck.

Breizh

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Edited by breizh, 11 May 2020 - 07:59 AM.


#3 Chemitofreak

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Posted 11 May 2020 - 05:48 AM

Hi,

 

If you are doing adequacy check then you need to do the following

 

1) Scenario review: As Breizh pointed out, you need to review the HAZOP. If that is not available, you need to study the P&IDs for all possible upset scenarios. There are some guidelines for scenario description available in API 521

 

2) Based on the scenario review you need to redo the calculations to prove the adequacy of the existing relief valve (API 520).

 

3) You also need to check the Relief valve inlet and outlet line hydraulics 


Edited by Chemitofreak, 11 May 2020 - 05:52 AM.


#4 fallah

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Posted 13 May 2020 - 03:16 AM

 

I intend to check capacities of installed relief valves at ammonia plant. The objective is to limit operation of plant load higher than the design relieving capacities of RVs as we are operating plant at load higher than the design. Since API-520 is for sizing the RVs, however in my case, I just only need to perform a capacity check,

 

So kindly suggest which standard or method should i follow. Also, do i need to consider different scenarios in this evaluation such as fire case or non fire case, block valve case etc.

 

 

Hi,

 

As you are going to operate the plant at a load higher than the design one, you need to increase the load step by step and recalculate the relief load of each RV for relevant governing scenario in each step based on the new load. Then repeat the load increment till the new relief load would lead to passed over the design capacity of one (or several) RV. The load corresponding to the step in which there is no passing over the design capacities of all RVs but the next step will lead to passing the design capacity of at least one RV over, could be considered as the limiting load for the plant load increment.

 

Of course, in the plant load increment other process parameters such as fluid velocity in the lines should also be checked with the limitations in the relevant plant design criteria.






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