gpl20
Chemical
- Aug 23, 2004
- 4
Hi all,
apologies if this process is described elsewhere but I have tried a search and can't seem to find the precise answer that I want.
Background:
A vessel has existing PSVs installed, these were designed for fire relief. As part of a modification there is a new relief case greater than the existing sizing case (vapour).
The steps I need to do are:
1) Calculate new relief case - done
2) Calculate what size orifice is required from relief valve sizing calc - done.
I used GPSA (5-7) for vapour relief.
The answer from 2) above meant that for the new relief case I would need to increase the orifice size from D to E. This is possible in the 1"x2" valve body, so no limitation physically there.
3) I need to determine if the existing installed tailpipes are adequately sized for the new rated relief case (max flow E orifice at relief conditions).
What are the steps I need to do to do this? I have API 520 (I/II) and 521 but to be honest I can't seem to get my head round it.
I have calculated the overall K factor (fl/d) for the downstream pipework using Crane "Flow of Fluids - Through valves, fittings and pipes". Though not sure if that will be useful or where the Mach number equations come into play that are provided in API 521 pages 106-108.
Any help in spelling out exactly what steps I now need to follow to 'size/rate' the existing tailpipes will be gratefully received!
Thanks.
I can happily provide specifics if it helps with clarification.
apologies if this process is described elsewhere but I have tried a search and can't seem to find the precise answer that I want.
Background:
A vessel has existing PSVs installed, these were designed for fire relief. As part of a modification there is a new relief case greater than the existing sizing case (vapour).
The steps I need to do are:
1) Calculate new relief case - done
2) Calculate what size orifice is required from relief valve sizing calc - done.
I used GPSA (5-7) for vapour relief.
The answer from 2) above meant that for the new relief case I would need to increase the orifice size from D to E. This is possible in the 1"x2" valve body, so no limitation physically there.
3) I need to determine if the existing installed tailpipes are adequately sized for the new rated relief case (max flow E orifice at relief conditions).
What are the steps I need to do to do this? I have API 520 (I/II) and 521 but to be honest I can't seem to get my head round it.
I have calculated the overall K factor (fl/d) for the downstream pipework using Crane "Flow of Fluids - Through valves, fittings and pipes". Though not sure if that will be useful or where the Mach number equations come into play that are provided in API 521 pages 106-108.
Any help in spelling out exactly what steps I now need to follow to 'size/rate' the existing tailpipes will be gratefully received!
Thanks.
I can happily provide specifics if it helps with clarification.