4 replies to this topic

[rbel038]

Hi All,

 

I have calculated capacity of our steam relieving system as per API 520 resistance to flow method. In parallel vendor has also done calculation based on our submitted datasheet to coefficient of discharge method.

 

Vendor has come up flow capacity that is slightly below my Kr method calculation (i have 155t/h and vendor has 146 t/h).

 

Is it typical that K method will give higher rated capacity than Kd? Or is it dependant on other system factors.

 

Thanks

[Bobby Strain]

I would use whatever ASME code requires. As an engineering contractor, I always made the vendor responsible for device sizing. And I checked the calculation. There should be no question as to the correct method to use for steam relief valves.

 

Bobby

[rbel038]

Thanks for your insight Bobby. I should also mention that these are actually Rupture Discs instead of a PSV. The conditions for calculating the capacity as per the Kd method are not applicable , hence why I have done the calculation per the Kr method.

 

My query was more that the vendors Kd sizing says that we would need to go up a size, however i am confident in our calculation as per the Kr method. Was looking for others experience in comparing the two methods

 

Thanks

Edited by rbel038, 22 October 2015 - 11:26 PM.

[breizh]

rbel038 ,

Consider this paper , it may help you .

Good luck.

 

Breizh

[Bobby Strain]

If you ignore the vendor sizing, then the responsibility is all yours. Your company may not appreciate this assumption of risk.

 

Bobby