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Reducer To Inlet Of Rupture Disk


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#1 hrfmny

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Posted 01 August 2010 - 07:38 PM

I know as a rule piping size downstream of rupture disk should not be decreased to reduce back pressure. But for upstream of a rupture disk, can a reducer (6" x 4") be installed between the vessel outlet (6") and the rupture disk (with a 4" inlet)?

Many thanks

#2 Art Montemayor

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Posted 01 August 2010 - 09:32 PM


We don't have enough basic data on your application to make a judgment on this question. For example, what is the calculated, worse case scenario size of rupture disk required for this vessel?


#3 Lowflo

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Posted 03 August 2010 - 10:48 AM

Be aware that there are no backpressure limitation, or inlet/outlet pressure drop limits for rupture disk installations. The only process detail that matters is the capacity of the installation. As long as the installation provides the necessary capacity to prevent the system from exceeding its maximum accumulation, then it's OK from a process perspective. The only potential issue with reducers, or any other fitting, is that of mechanical strength. If it's mechanically supported, you could have a 1" inlet to a 6" disk, or any other combination.

#4 djack77494

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Posted 04 August 2010 - 01:24 PM

Lowflo makes an excellent point that may be somewhat obscure to many people. The limitations on the inlets and outlets to many pressure relief devices were instituted because of the characteristics of the devices. For example, with a high pressure loss entering a PSV, the pressure right at the device will be high enough to pop the valve, but will then drop due to hydraulic losses. This may cause the valve to rapidly cycle, known as chattering. High outlet pressures due to relief flows cause their own set of problems and therefore must be avoided. However, if you use alternate devices without these limitations, then the restrictions no longer apply. The limitations you apply for a conventional safety valve are more stringent that what would be applied to a balanced bellows PSV or a pilot operated PSV or a rupture disk. What many people think of as "rules of thumb" must be applied with the knowledge of when they are and are not applicable. Rarely in engineering does "one size fits all".

#5 fallah

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Posted 05 August 2010 - 02:50 AM

Be aware that there are no backpressure limitation, or inlet/outlet pressure drop limits for rupture disk installations.


Certainly you don't mean Superimposed Back pressure that its variation would significantly affect Bursting Pressure of the Rupture Disc.




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