Excess Flow Valve for Rupture Disk Installation
Excess Flow Valve for Rupture Disk Installation
(OP)
Excess flow valve is regarded as a accessory for Rupture Disk installation. Not quite sure the purpose of it. Please advise.
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
Excess Flow Valve for Rupture Disk Installation
|
Excess Flow Valve for Rupture Disk InstallationExcess Flow Valve for Rupture Disk Installation(OP)
Excess flow valve is regarded as a accessory for Rupture Disk installation. Not quite sure the purpose of it. Please advise.
Red Flag SubmittedThank you for helping keep Eng-Tips Forums free from inappropriate posts. Reply To This ThreadPosting in the Eng-Tips forums is a member-only feature.Click Here to join Eng-Tips and talk with other members! |
ResourcesWhat is rapid injection molding? For engineers working with tight product design timelines, rapid injection molding can be a critical tool for prototyping and testing functional models. Download Now
The world has changed considerably since the 1980s, when CAD first started displacing drafting tables. Download Now
Prototyping has always been a critical part of product development. Download Now
As the cloud is increasingly adopted for product development, questions remain as to just how cloud software tools compare to on-premise solutions. Download Now
|
RE: Excess Flow Valve for Rupture Disk Installation
Most excess flow valves I've seen are used on railcars and tank trucks to limit the spill rate if the outlet valve gets sheared off in a wreck.
Good luck,
Latexman
RE: Excess Flow Valve for Rupture Disk Installation
1) Starting at the vessel being protected,
2) Fluid flows to rupture disk, then
3) Through a tee fitting.
4) In the branch of the tee, locate the excess flow valve.
5) One side of the excess flow valve is connected to the tee.
6) The other side of the excess flow valve is open to atmosphere or other suitable destination.
7) Install the excess flow valve so that high flowrates from the tee to atmosphere will cause the valve to close.
8) Install a pressure gauge upstream or downstream of the tee.
9) Install the PSV downstream of the pressure gauge connection.
The idea is that the rupture disk could develop a leak. You want to know about the leak so you can replace the rupture disk. Presumably, it is undesirable to have the PSV pop, else why even bother with the rupture disk. Thus if the rupture disk actually pops due to overpressure, the excess flow valve will close and the full pressure will be experienced at the PSV inlet. The pressure gauge will indicate this high pressure, so it will be apparent that the rupture disk has burst.
Instead, if the rupture disk just develops a small leak, it will escape through the excess flow valve.
That's what I've seen. As I think about it, I believe the situations where you would want this type of performance are quite limited.
Doug
RE: Excess Flow Valve for Rupture Disk Installation
A rupture disc ahead of a PSV is common in situations such as corrosive service.
It is expensive to have a PSV with the metallurgy to match the process fluid corrosion. It is much cheaper to use a rupture disc, with the correct metallurgy.
In relieving case, on over pressure, the rupture disc ruptures, the pressure reaches the PSV, and the PSV relieves.
In normal case, the process fluid only contacts the rupture disc. Hence, the PSV can be non-exotic metallurgy.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: Excess Flow Valve for Rupture Disk Installation
My own experience of the simplest installation of excess flow valves as a small tubing size device (1/4" or so diameter), mounted into a 3/8" or 1/2" threaded well on the rupture disk holder (i.e. the two steel rings that clamp onto the disk and hold it). Typically a small gage is also mounted at that point via branch on a tubing tee.
If the rupture disk leaks, or more likely if the disk has burst during an upset which was not reported, the pressure on the gage can be used to determine this. If the disk is good the gage is reading atmospheric, if bad it is reading process.
These excess flow valves often leak just a little, and any condensible fluid will slowly drip out forming a small oil spot below- another sure sign the disk is bad.
On the otherhand you can get as complicated as you want- many times I have seen pressure transmitters broadcasting the rupture disk status to the panel. This can be nice as gages eventually go bad, but it is obviously some extra cost. As an added note, the gage needs to be able to read process pressure. I have seen a few times improperly specified low pressure gages on failed rupture disks completely "wrapped" back to near zero giving a false reading that everything is ok.
best wishes,
sshep