9 replies to this topic

[fmalik]

Hello,
When adding multiple psvs to a vessel (fire case) is the total relief rate just divided by 2 in case the two psvs (same type) are added. API doesn't explicitly mention this therefore I wanted to confirm.
Regards,

[latexman]

Each does not have to be exactly half. But yes, the sum of the 2 PSV’s capacities must be >= the total relief rate. Both are required to relieve the vessel.

Some companies put a second PSV as an inline spare. In this case, each PSV’s capacity must be >= the total relief rate.

[fallah]

When adding multiple psvs to a vessel (fire case) is the total relief rate just divided by 2 in case the two psvs (same type) are added. API doesn't explicitly mention this therefore I wanted to confirm.
 

Hi,

 

When sizing for multiple valve applications, the total required area is calculated based on an overpressure of 16% or 4 psi, whichever is greater (for fire case 21%). Then two PSVs with the same size would be selected to cover the calculated total required area. Hence the relief loads of such two PSVs might or might not be equal.

Edited by fallah, 03 December 2023 - 07:37 AM.

[latexman]

Under fire emergency conditions, pressure relief devices (1 or more) must be capable of preventing the vessel pressure from rising more than 21 percent above the MAWP.

[shvet1]

When adding multiple psvs to a vessel (fire case) is the total relief rate just divided by 2 in case the two psvs (same type) are added. 

 

API allows 1st PSV 80 cfps capacity, 2nd PSV 20 cfps capacity while firecase relief is 90 cfps.

[latexman]

API allows 1st PSV 80 cfps capacity, 2nd PSV 20 cfps capacity while firecase relief is 90 cfps.

 

cfps?  API # and section, please?

[latexman]

 

When adding multiple psvs to a vessel (fire case) is the total relief rate just divided by 2 in case the two psvs (same type) are added. API doesn't explicitly mention this therefore I wanted to confirm.

 

API 520 Part 1 says:

 Capture 1.JPG   29.35KB   4 downloads

 Capture 2.JPG   64.04KB   2 downloads

[breizh]

Hi,

To add to the discussion, consider the documents from Lesser and from Crosby (with examples)

Breizh

Attached Files

•  safety valves calculation CROSBY.pdf   1.45MB   42 downloads
•  EHB_en_7-Sizing.pdf   4.77MB   47 downloads

[shvet1]

Sorry for delay, I have been away from computer for a week.

 

 

API allows 1st PSV 80 cfps capacity, 2nd PSV 20 cfps capacity while firecase relief is 90 cfps.

 

cfps?  

 

 

cfps = cubic feet per second

 

 

API allows 1st PSV 80 cfps capacity, 2nd PSV 20 cfps capacity while firecase relief is 90 cfps.

 

API # and section, please?

This is a reference to the statement you provided before

Each does not have to be exactly half. But yes, the sum of the 2 PSV’s capacities must be >= the total relief rate. 

[latexman]

Thx!