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Kd Values For Psv Sizing


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#1 aniljani

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Posted 21 April 2017 - 10:04 PM

Hi ,

I am currently working in FEED project for Hydrocarbon Gas processing Plant and doing PSV sizing calc.
In Sizing calculations, we are using Kd values with 90% derating factor as prescribed in ASME (Certified Kd is 90% of avg from tests done)for required area estimation and the rated capacity is based on API effective orifice areas as in API-526 in the absence of Manufacturer valve selection.

As an example,in one case, we got required relief area as 6.48 inch2 with Kd value 0.88 and we selected API Q orifice. Had we used Kd = 0.975, P orifice size would have been sufficient, and in some other cases, no. of PSV required are varying for required relief.

Can we follow this practice for FEED level project...Please clarify...

#2 breizh

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Posted 22 April 2017 - 06:35 AM

hi ,

Take a look at the document attached , you should find your answer .

 

Hope this is helping you.

Breizh


Edited by breizh, 22 April 2017 - 07:10 AM.


#3 breizh

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Posted 22 April 2017 - 07:13 AM

hi ,

Take a look at the document attached , you should find your answer .

 

Hope this is helping you.

Breizh

 



#4 Bobby Strain

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Posted 22 April 2017 - 07:54 PM

You should size based on ASME basis if this is required. If this is the case,use the "Red Book" to get manufacturers area values.

 

Bobby



#5 aniljani

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Posted 22 April 2017 - 08:25 PM

Thanks Breizh and Bobby for you response..

#6 gegio1960

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Posted 23 April 2017 - 01:25 AM

aniljani,

if you are a process engineer your method, enriched by Breizh and Bobby Strain comments, is enough.

But, obviously, the final choices are in the hands of the manufacturer of each PSV.

Good luck!



#7 ChemEng01

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Posted 30 April 2017 - 01:37 AM

If you are doing FEED, it is preliminary sizing, you are using API effective areas use kd =  0.975 for vapour.

 

If you are are using actual area of a selected valve then use K factor supplied in red book for vapour.

 

Either use API effective area & API Kd for sizing OR;

 

use ASME area & ASME K for sizing

 

 

Your result for selected valve size should be similar. Just don't mix the API / ASME. 


Edited by ChemEng01, 30 April 2017 - 01:47 AM.





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