2 replies to this topic

[jakjak]

Hi,
I have went over some parts of the API RP-520 and ASME XIII on PRV, hoping to figure out some design guideline for a pressure vessel I am working on. I wonder if anyone can give me pointers on this?
Here goes:
We have a pressure vessel that has a port added on top to relieve pressure build-up. Over the port, we have a spring-loaded disc that sit over the port for pressure relief. To ensure better sealing, we have made a groove over the port and added an o-ring. Here are some dimensions for the port, groove and disc:
port diam : 0.5"
groove diam: 0.9"
disc diam : 1.1"
What i am trying to find out is, how do we size the spring so that the spring force is sufficient to hold the pressure at its MAWP and open when overpressure occurs ? Based on the diameters, we will have different areas when lifting start to occur, we think that the force exerted by the pressure will vary with area.
Can anyone shed some lights on this? Any help is appreciated.

[pleckner]

RED FLAG TIME!!!

Is this a new nozzle being added to an existing pressure vessel?? If so, then it needs to be recertified by a contractor who is allowed by Code to perform this task. You can't just use anybody to do it.

Whether this is a recertification issue or not, you cannot design any type of relief device for a Coded vessel unless you are a Code shop that performs this type of work...PERIOD! If this is not a Coded vessel but will see a pressure greater than 15 psig, then it needs to be a Coded vessel and you still can't design any type of relief device...PERIOD!

You need to determine the relieving rates for all credible scenarios that can cause over pressure and give that information to one or more of the many vendors of relief protection devices that are out there. If you need help with this exercise, just post any specific quesitons you may have and perhaps we will be able to help you out.

And one more thing, I don't really care what part of the world you are in (USA or other), over pressure can kill and this vessel must be designed to ASME Section VIII, Division 1 standards (or equivalent) and a properly designed and certified pressure relief device be installed....PERIOD!!

I hope I'm not sounding too harsh but this is truly a very dangerous path you are embarking on!!

[Nirav]

Hi,
I have went over some parts of the API RP-520 and ASME XIII on PRV, hoping to figure out some design guideline for a pressure vessel I am working on. I wonder if anyone can give me pointers on this?
Here goes:
We have a pressure vessel that has a port added on top to relieve pressure build-up. Over the port, we have a spring-loaded disc that sit over the port for pressure relief. To ensure better sealing, we have made a groove over the port and added an o-ring. Here are some dimensions for the port, groove and disc:
port diam : 0.5"
groove diam: 0.9"
disc diam : 1.1"
What i am trying to find out is, how do we size the spring so that the spring force is sufficient to hold the pressure at its MAWP and open when overpressure occurs ? Based on the diameters, we will have different areas when lifting start to occur, we think that the force exerted by the pressure will vary with area.
Can anyone shed some lights on this? Any help is appreciated.

I am guessing that you are trying to manufacture a kind of alternative to PSV or PSV by yourself.
I hope my guess is wrong. If it is true, you are making BIG MISTAKE. The reasons already explained by Phil.