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Supplemental Valve In Api 520 Part 1


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#1 christopherchoa

christopherchoa

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Posted 11 October 2018 - 09:01 PM

Hi All,

 

The supplemental PSV as discussed in API 520 Part 1) set pressure can be at 110% of MAWP. Essentially this is for fire case in addition of devices (set pressure at 100% MAWP) sized for non-fire cases.

 

I'm working with a company where a single PSV set pressure is at 110% MAWP (there is no other PSV).

 

My question is: is it possible to have one supplemental PSV without the primary PSV? Any possibilities of this happening, guys?

 

e.g.

Design Pressure = MAWP = 10.2 MPag

PSV set pressure = 11.22 MPag

 

 

 



#2 fallah

fallah

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Posted 11 October 2018 - 11:10 PM

Hi All,

 

The supplemental PSV as discussed in API 520 Part 1) set pressure can be at 110% of MAWP. Essentially this is for fire case in addition of devices (set pressure at 100% MAWP) sized for non-fire cases.

 

I'm working with a company where a single PSV set pressure is at 110% MAWP (there is no other PSV).

 

My question is: is it possible to have one supplemental PSV without the primary PSV? Any possibilities of this happening, guys?

 

e.g.

Design Pressure = MAWP = 10.2 MPag

PSV set pressure = 11.22 MPag

 

cheristopherchoa,

 

The case you described isn't in compliance with the definition provided in API 521 Part I; but on the other hand haven't any contradiction with the concept of PSV setting for fire case, as the relieving pressure wouldn't pass the 1.21 times of MAWP.

 

It might the designer had a thinking in his/her mind using a smaller PSV for fire case; especially when he/she had seen the only case for overpressure of relevant vessel is fire case.






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