TiCl4
Chemical
- May 1, 2019
- 632
I have a vessel with MAWP of 50 psig, with relief case required of 920 lb/hr of steam. I've selected a Kunkle 910-series, with rated capacity of 1,062 lb/hr steam. The PSV will be directly mounted on the tank nozzle, and will discharge through a tailpipe. The tailpipe exact routing is TBD, as we are still in design phase, but total equivalent length will be <50'. Steam quality after expansion through the PSV will be approximately 0.92. I know this isn't a huge amount of water, but I wanted to evaluate the tailpipe pressure drop through a two-phase model to ensure we stayed under the 10% built-up backpressure limit of the conventional PSV. I've built a spreadsheet to evaluate pressure losses using Friedel's model, and had a few questions:
First, based on two-phase flow evaluations from research papers, "good" two-phase flow models seem to have a standard variance of 30-40% from reality. Have you found this to be the general case for 2-phase flow models? In my case, if I discharge through 100' equivalent of 2" schedule 10S pipe, I'll have a calculated BBP of ~2.2 psig. My allowable BBP is 5 psig, so even with a 40% factor added to the 2.2 psig, I am still under the 10% limit. Is this approach sound?
If the calculated BBP were instead 4 psig, what would you do, given the inherent uncertainty with two-phase flow calcs? Would you limit the BBP to 5psig/1.4 = 3.6 psig, or would you take another approach?
Secondly, using API 521 approach to estimate sound energy, I get 120 decibels at a distance of 2 meters. Given this PSV is discharging through a tailpipe instead of straight to atmosphere, is this noise calcuation an estimation at the actual relief point at the end of the tailpipe, which is away from operators, or at the PSV itself, which is near operators? I assume the PSV discharging into a pipe would attentuate the noise for nearby operators, but don't have any experience to suggest what an actual attenuation value would be.
First, based on two-phase flow evaluations from research papers, "good" two-phase flow models seem to have a standard variance of 30-40% from reality. Have you found this to be the general case for 2-phase flow models? In my case, if I discharge through 100' equivalent of 2" schedule 10S pipe, I'll have a calculated BBP of ~2.2 psig. My allowable BBP is 5 psig, so even with a 40% factor added to the 2.2 psig, I am still under the 10% limit. Is this approach sound?
If the calculated BBP were instead 4 psig, what would you do, given the inherent uncertainty with two-phase flow calcs? Would you limit the BBP to 5psig/1.4 = 3.6 psig, or would you take another approach?
Secondly, using API 521 approach to estimate sound energy, I get 120 decibels at a distance of 2 meters. Given this PSV is discharging through a tailpipe instead of straight to atmosphere, is this noise calcuation an estimation at the actual relief point at the end of the tailpipe, which is away from operators, or at the PSV itself, which is near operators? I assume the PSV discharging into a pipe would attentuate the noise for nearby operators, but don't have any experience to suggest what an actual attenuation value would be.
