I'm a little stuck. I have been looking into this and find all the issues associated with a small approach temperature on an exchanger.
Conditions: I have a BEU heat exchanger acting as an overhead condenser. I have an organic vapor entering the shell at 430°F and distillate leaving the...
Does your pump manufacturer not offer an internal relief option? Are you sure that your pump currently does not have an internal relief device?
In either case a RD is not a good option for reasons already discussed.
The PSV could be sized for the relief of the tube rupture scenario or a fire case scenario.
It is really difficult to make these types of decisions on a forum. You should consider having this system evaluated by a experienced relief design person at your plant, if there is real cause for concern.
You should consider getting the following paper.
'Vent sizing for fire considerations: external fire duration, jacketed
vessels and heat flux variations owing to fuel composition'
mbt22 and met11 are correct case B is invalid.
When you boil and relieve your hot oil your tank will experience tempering and stay at a equilibrium temperature. Any nitrogen relieved will be equivalent to a volume of oil as the oil is pushing out the N2, basically.
So just size for hot oil...
Set Pressure is not calculated. You need to determine what is appropriate for your project.
After you find your flow rate. You perform a hydraulic calculation to find your built up back pressure.
Superimposed back pressure is static and you will need to determine this by downstream conditions...
Yes, you would have greater pressure drop through the sch160 line.
But what is important is not that there is less area to flow fluid. But whether if you have 3% or less pressure drop through that line if you are required to satisfy ASME VIII & API.
I'm only going to recommend a path forward.
1. Take the PSV out of service and send it to a valve repair shop so they can maintain it and see what it is internally.
2. Make sure that you understand the correct size and just replace the thing.
At my plant we would probably just go with...
You really do want some sort of bend in the discharge pipe. The tail pipe should also preferentially have a weather cover on it. Putting some discharge pipe on the PSV helps to reduce debris which could enter the device. It can also help to keep anyone from sticking a screw driver or something...
At the plant I'm at the people who came up with a plan of attack prioritized on the most hazardous applications, safety critical and then 'everything else'. Essentially what you did.
Once you have those buckets filled I would go with.
1. Incorrect orifice (I'm assuming this takes care of...
I know from personal experience how difficult it can be to pipe up these highly viscous fluids.
One thing I didn't notice anyone else commenting on. If the gate valve is on a line you are designating as your 'relief path' you should only have a full bore valve.
API 520 part 2 includes...
You should look to API 520 Part 2.
API 520 Part 2 breaks down the guidelines for the design of proper discharge line design.
There is far too much information there for me to adequately break it down in a forum post. However, after you review the document you can feel free to come back and...
Is there a tank upstream of the pump?
Typically in a situation like this I would want to send my relieved material back to the tank. But I am not sure if that is an option for you.
If all of these TRVs are in close proximity you might need to install a small catch tank.
This type of issue is always a grey area. As others have said before you need to determine the risk associated with that pump relief valve failing. I agree with those who pointed out they may be failed for a prolonged period of time. Unless they fail open you can be sure that they are forgotten...
