Rupture Disc Application?
Rupture Disc Application?
(OP)
I am looking into using a rupture disc in a simple system (1/8" Stainless Steel tubing) to protect a very expensive pressure transducer. For expample, the guage is used upto 300psi, but it will break at 330, and so i need the rupture disc to go off if the pressure gets to about 320psi but not before 300psi.
Am I barking up the wrong tree, or is this a feasible application?
PS. It gets easier, because the 1000psi transducer breaks at 1100psi, and so the disc shoudl blow between 1030 and about 1090...
Any ideas?
Thanks,
rcontractor
Am I barking up the wrong tree, or is this a feasible application?
PS. It gets easier, because the 1000psi transducer breaks at 1100psi, and so the disc shoudl blow between 1030 and about 1090...
Any ideas?
Thanks,
rcontractor





RE: Rupture Disc Application?
If the disk is set to go at 320 psig and you are operating at 300 psig, that is nearly 94% of set point, close for a rupture disk I believe (fatigue due to pressure cycling is another question to raise with them).
If you want the disk in service, set at a nominal 320 psig, to not fail above 330 psig, you need an accuracy of 3%. Again, that is doeable but I believe tighter than the standard deviation they will quote.
There's a couple of people here who are much better in this area than I am, hopefully they will add their opinions.
You've lost me on the second part with the transducer, is this another rupture disk on an associated system?
RE: Rupture Disc Application?
Thats what I thought in terms of the fatigue life of the disc. I will be in contact with a vendor later today and see what they have to say as well.
The second part comes out of nowhere, I apologize. I need to size several rupture discs for several different transducers. Each transducer is used separately in the system and then replaced with a higher one to achieve more accurate calibration. I hope this makes sense.
RE: Rupture Disc Application?
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RE: Rupture Disc Application?
Remember, the accuracy of the guage or transducer is best at the midrange of its scale. Operating so close to its failure point is going to give inaccurate readings.
saxon
RE: Rupture Disc Application?
A very valid observation, and one that I had myself once they started me on this mini-project. However, this process has been running long before I got here and the people here are very qualified. I will ask this question to them, as it puzzles me too, but I think it's already been dealt with....
thank you
RE: Rupture Disc Application?
J. Alton Cox
www.delucatest.com
RE: Rupture Disc Application?
For an 1/8" Union Type safety Head you cannot get a burst pressure as low as 330 psig. You might get a 1000 psi disk; but then your problem will be the limitation that operating presssure not exceed 90% or 95% of the stamped (marked) burst pressure.
If you go to other type rupture disks even with a 0% Manufacturing Range, the 5% Burst Disk Tolerance the code allows will cause you to exceed desired range.
For you first example assuming a 315 psig stamped burst pressure:
MAWP = 330 Psig, with a stamped burst pressure of 315psig with a 0% manufacturing range = Stamped Burst Pressure of 315. Accounting for +/-5% TOLERANCE (DIFFERENT FROM MFG RANGE) = 315 +/- 15.75 psi or an allowable actual burst pressure range (versus being stamped at 315 psig) for the disk of 299.25 psig to 330.75 psig. This is unaccepatble and any other selected stamped burst pressure is even further outside your spec on either the l;ow or the high side!
Seek another way.
The more you learn, the less you are certain of.
RE: Rupture Disc Application?
By the way, your spec seem very ODD! I interpret your memo to say that the MAX NORMAL operating pressure is 300 psig and that the transducer actually fails at 330 psig.
Normally we design vessels and other equipment to have an allowable overpressure above its design pressure (or MAWP) for relieving purposes.
For example, if the MAX NORMAL operating pressure was to be 300 psig and you wanted to design a vessel for this you would proceed as follows:
300 / 0.9 = 333.3 psig = min design pressure (normally I would round this up but we'll not do this here). The 0.9 allows a min margin between relief device setpoint and desing pressure of vessel.
333.3 x 1.1 = 366.67 = allowable overpressure at required relieving rate (this can be as high as 1.21 normally except for occasional overpressures in piping. The relief device cannot be set higher than 333.3 psig in this example = Design Pressure or MAWP.
The Vessel is then hydro'd, older vessels were hydro'd at 1.5 the design pressure (it can now be reduced to I believe 1.3); plus the ASME Code has a built in safety factor of about 4, so the actual FAILURE pressure for the tank would approximate (lets use 1.5 ratio):
Hydro tested at 333.3 x 1.5 = 499.95 psig
Failure pressure = 333.3 x 4 = 1333.2 psig; we take no credit for this at all, it just gives you an idea where the actual catastrophic failure pressure may be without a finite elelment analysis.
The more you learn, the less you are certain of.
RE: Rupture Disc Application?
The system I am dealing with is a calibration system with MAWP way above what is being dealt with. The Quartz pressure transducers are most accurate at their maximum range and that is why they are used that high. The only concern I have is that there is only a 30-40psi window within which the rupture disc should burst.
My inclination at this point is to source out a system similar to that suggested by JAlton and get it as close to the operating pressure we require as possible.
I apologize for not being more descriptive in my first thread, and thank you for all your suggestions and advice...
RE: Rupture Disc Application?
Have you considered a solenoid-operated slam-valve that is driven off your quartz transducer? Two valves (one to block the process and one to vent the transducer) would be reasonably inexpensive in 1/8" service and can be set to be very accurate. Neither rupture-disks nor PSV's will give you the precision that it looks like this application requires. I'd put in a spec-break.
David
RE: Rupture Disc Application?
That sounds like a really good idea. However, I dont' quite know what you mean by "put in a spec-break." Also, if you have any vendors you would recommend, I would much appreciate that.
Thank you for your advice.
Ras
RE: Rupture Disc Application?
J. Alton Cox
www.delucatest.com
RE: Rupture Disc Application?
A "spec break" is simply a break between one specification (generally either temperature or pressure rating) and another. If you put a slam valve between a pressure source and a lower-rated device it is generally called a "spec break". Sorry about lapsing into short-speak.
I'm just a flangehead. When I need to pump something as small as an electron, I always call the I&E guys and they speak very slowly to me and we get what we need. Can't tell you what brand of solenoid valves they're using this month.
David
RE: Rupture Disc Application?
I was talking to a vendor on Friday about one of my projects and we got to talking about solenoid valves. Your problem came up and he suggested a 3-way solenoid valve (to be able to slam and vent with one valve). He said Peter-Paul or Ashcroft both have excellent 3-way valves for around $US90.
David
RE: Rupture Disc Application?
I won't write much because the website explains a lot itself
http://www.burnspressuresystems.com/Products/Rupturepin/rupturepin.htm
Your opinion shall be appreciated.
Regards,
FLUIDM
RE: Rupture Disc Application?
J. Alton Cox
www.delucatest.com
RE: Rupture Disc Application?
The more you learn, the less you are certain of.
RE: Rupture Disc Application?
Maybe you should change your transducer. Check what is the signal output and inquire from other pressure transducer vendor. You might find a specification that matches your requirement. Maybe a pressure transmitter can do the job.
rgds,
209larry