Use of rupture pin shutdown valves

[Diborane]

It is easier to explain my question with an example.

The MAWP of pressure component (vessel/heat exchanger, excetera) is 90 psig. Pumping into the component is a pump capable of putting out 120 psig at a zero-flow condition. This condition could happen if a valve downstream of the vessel was shut. The vessel would need to be protected against this case using an SRV, rupture disk, or rupture pin.

My question involes whether the use of a rupture pin shutdown valve upstream of the pressure component is sufficient protection (and code acceptable) from overpressure do to a pump at a low flow/zero-flow condition. Of course a SRV would still be required for other possible overpressure events such as thermal expansion.

http://www.rupturepin.com/rpbucklinga3.html

The device is a automatic, doesn't require operator intervention, and works on the same principle as a rupture pin valve. The biggest weakness I can see is something getting caught in the valve and preventing it from closing (I have heard of wrenches being found in the bottom of tanks so I can imagine this happening).

Diborane

 

[Montemayor]

Diborane:

I don't believe your concept and proposal meets with ASME's intent on furnishing positive pressure relief to a pressure vessel - and, as such, would not be sanctioned by ASME.

But why go that route? All you have to do is install a pressure relief device (PSV, Rupture Pin, or a Rupture Disk) directly on the vessel in question and you will comply with ASME's demand.

 

[Diborane]

Montemayor

Thank you for you reply. As I’ve read through the previous posts in the engineering forums that interest me I have always found your responses quite enlightening. If you were my supervisor I could keep you occupied with many engineering questions that I have for a long time.

In the past all of our vessels have been protected as you said. My thought process was that the pressure vessel needs to be protected against possible overpressure scenarios. The use of a shutoff valve since it can’t be bypassed and is not operator controlled would make that scenario not likely (it would entail the failure of both the shutoff valve [which operates on the same principle as a rupture pin] and the cause of an overpressure event).

The reasoning for why a shut-off valve in this case would be preferable is two-fold. First I can see it decreasing capital costs. A rupture pin must be sized to relieve the determined necessary flow, say this requires a 14” rupture pin on the vessel, additional piping, and a safe receiver. A much smaller shutoff valve could be used at the expense of friction loss in the line feeding the vessel.

My second thought was that a shut-off valve is much easier to spec than a rupture pin device. The shutoff valve would only require a shut-off DP and a shut-off set point. A rupture-pin requires calculating a relieving flow and sizing the orifice area based on the resistance of flow. This can be extremely difficult for two phase systems and non-Newtonian fluids.

In any case thank you for you advice I will take the idea and throw it in the circular file.

 

[djack77494]

Diborane,
I'm inclined to agree with Art Montemayor. Locate the rupture pin valve, SRV, rupture disk, etc. in or on the vessel and you're done. If you stay with your plan, you will need to consider the upstream (shutoff) valve leaking, and size a vessel mounted relief device for that contingency. Then, what will your flowrate be for leakage through your valve? It's certainly a credible scenario (i.e. not double jeopardy) to believe your shutdown valve will not be leaktight. So you'll be faced with trying to develop a reasonable estimate for leakage. If your source of overpressure is a pump, you have a known volume of fluid to relieve, and though I know there are some very large pumps out there, needing a 14" valve would be amazing. (Unless you're talking about a flashing liquid.) Also, don't forget to consider that you've shutdown, blocked in your vessel, and then have a pool fire beneath it.
Doug