Without looking at the specific system, I can only offer general advice. There are two primary fire cases typically evaluated: vapor generation, gas expansion.
Fire - Vapor Generation
In this case you're typcially protecting vessels with a constant liquid level. Most vessels have an upper...
If you truly have been looking at more than just basic PSV sizing calcs themselves, I would use the phrasing "relief systems" rather than just "relief valves".
Sizing "relief valves" reads to me like someone completing plug-and-chug equations pulled from API-520/521. Designing and evaluating...
Are you saying you add the volume of the combined liquid volume of the trays (subracting the bubble caps) to the liquid volume of the sump and take THAT wetted area? That's not what whammett's equation above implies.
Either way, I would never advise someone to take the bubble caps into...
Again, the equation for sizing a relief valve for a fire vapor case is based on wetted AREA. We're not talking VOLUME. The API equation is not based off volume but area.
Yes you add the wetted area of the sump to the wetted area of the trays. But this area is the outside area of the fluid...
@Casimo5
What you're saying is correct- you do want a PSV set pressure to take into account inlet line losses if they're significant (> 3% to 5%).
However I would still be very hesitant to place a new relief valve at the end of a chain of equipment like that. Pressure drop is not always a...
I do not believe accounting for bubble caps is more accurate.
The formula in my original post is based off the surface area for a cylinder and should only be the wetted *sides* of the column. The trays themselves are not exposed to the fire, but the walls of the vessel are exposed. We're not...
I assume you're refering to a fire-vapor case?
If so, I generally assume the normal liquid level at the bottom of the column added to the with the total liquid holdup in all the trays. Multiply that combined level by the circumference of the column.
Wetted Area = 2*pi*r*(N*l + L) + [surface...
In the afternoon test, they will give you a booklet with all the questions for all the afternoon tests and you bubble in on the answer sheet which exam you took (chem, mech, civil, etc). This is nice because you can spend a couple minutes looking at each section to assess which is easier.
That...
@TDAA:
You're a little hung up on semantics. By "resigning", I mean leaving a company without something else lined up. Which is the case with westheimer1234. Giving notice in order to work somewhere else is a totally different situation.
@BenThayer: That's a very good point.
Let's say you size the above PSV example for an upstream operational pressure of 150 psig.
Picture yourself walking into this plant and you see a pressure gauge on the equipment reading 155 psig. How comfortable are you standing there? Maybe the gauge...
@RoyTyrel:
People do and should care about employee reliability and consistency. It's not a "loyal pet" employers want so much as someone who can be expected to take a reasonable degree of stress and not leave mid-project. Egos sometimes clash on a project and emotions can run high but most...
@Latexman: I was speaking for a completely hypothetical but let's say the control valve is an FCV taking plant air from an accumulator to a downstream user. That's a case where operations may be tempted to increase the pressure to increase the holding capacity of the vessel.
Manually relieving...
Resigning is an impulse and is not very attractive to future employers. Without being a fly on the wall in an interview to know more, the most likely cause of failing your interviews is perhaps your explanation for leaving the previous company.
Resigning for anything other than serious ethical...
Another situation where you would deviate from the equipment MAWP as a PSV set is when a client is cobbling together a plant with used equipment from all over the place.
Say you have Vessel A with a 450 psig MAWP and Vessel B downstream with a 600 psig MAWP. Assume no rotating equipment in...
