API526 (Rating clarification) 1

[Hari PRV]

Hi,
Can anyone clarify my below doubt,

Example: The orifice "3K6" has a minimal starting rating from 900x150,if it is suitable for pressure rating of 900x150 why it is not available with 150x150,300x150...etc, ratings?

Thanks in advance.

 

[mk3223]

IMO, the relief capacity of the PSV with different orifice sizes of the same pressure rating may be overlapped with each other. For example, the capacity of valves 3"K"6 CL.600x150 or 300x150 may be covered by other orifice size of valves, such as either "J" or "L" orifice valves of the same pressure rating class.

 

[Hari PRV]

Ok Noted,

1. But here 3K6 is a unique size, i.e. No other orifice has this same inlet/outlet size (3x6) per API 526.Hence for this case we cannot overlap it with other orifices unless/untill I change my inlet/outlet size.
2. Can you also clarify what are the deciding factors that links valve size with its rating in API 526.Is it purely due to pressure?

Thanks in advance.

 

[mk3223]

IMO, the valve sizes listed in API 526 could be decided together by the API Committee and the Manufacturer. In my opinion, the Code is reviewed periodically, and can be updated if necessary.

 

[Hari PRV]

Noted,
Thanks for spending your time.