Rupture disc versus PSV for HEX Tube Rupture case

[DoraeS]

Hi all,
If I have a HEX tube rupture case, and 10/13 rule is not applied in this case for the LP side. The question is, can I install a PSV which sized for tube rupture flow? Or it is always prudent to have rupture disc installed? Does anyone know if PSV can be used for tube rupture case?
Thanks.

 

[psafety]

Sure a PSV can be used. Did it in the past on a S/T heat exchanger in 400-lb steam/frying oil application.

 

[lizking]

Depends largely on fluids. Gas on tubeside (high pressure side)and liquid on shellside with more than a 1000 psi differential warrants a transient analysis.

 

[MJCronin]

Ummm....

Depends also on maintenance department and how often you expect the event to happen.

PSVs usually, (but not always) will reseat.

You have to weigh the operations and maintenance consequences of disk replacement versus possible valve "stuck-open"

Additionally, the PSV, if made from exotic materials can cost a whole lot more..

Your call...

-MJC

 

[DoraeS]

Thanks to everyone here. My concern is, if there is any code or standard specifies that for tube rupture, PSV is not suitable (as not acting fast enough) and hence rupture disc is the solution.
Does anyone has any opinion on this?

 

[lizking]

That's what the transient analysis would tell you. Frequently, as you state, a PRV will not act fast enough. Also, the analysis will determine a required location of the relief device. Sometimes it must be right on the vessel (as opposed to the in/out piping).

 

[DoraeS]

Thanks lizking. Does anyone know what kind of software can be used for this transient analysis?

 

[JimCasey]

A safety-relief valve disc has a particular shape so that it begins to lift, it causes a reaction force in the fluid so that the disc "pops" open to the extent of its travel. This happens quite rapidly.

Your application would be governed by ASME section VIII in the US, and a PSV is acceptable to the ASME. That code is recognized as LAW in most states. It also allows for a Rupture disc. The hot setup is to use both. Put a nonfragmenting disc under a PSV. Same set pressure. If the disc bursts, the PSV pops. Then the valve reseats when the event has concluded. But during the valve's entire service life before that time it has never been exposed to the process fluid, so it should be in new condition. The code requires that you have a device between the disc and the valve to allow for (1) indication of a burst disc(2) testing of the valve. Your PSV vendor can supply this.