Pressure Relief for High Pressure Separator
Pressure Relief for High Pressure Separator
(OP)
I just started with a rupture disc company and we were approached to come up with a pressure relief solution for a High Pressure Separator. This is a relatively new application for my company, so I was hoping to get input on what solutions others have used for this application and their experiences with those solutions (good or bad).





RE: Pressure Relief for High Pressure Separator
Dejan IVANOVIC
Process Engineer, MSChE
RE: Pressure Relief for High Pressure Separator
Nothing personal - Good luck in your new job.
RE: Pressure Relief for High Pressure Separator
RE: Pressure Relief for High Pressure Separator
RE: Pressure Relief for High Pressure Separator
Best regards, Morten
RE: Pressure Relief for High Pressure Separator
Don1980, with the rupture disc solution you used, did it work well for your application? Any features/attributes you would have changed?
Thank you again for your help.
RE: Pressure Relief for High Pressure Separator
Presume you are aware of the risks associated with installing an RD in series with PSV.
RE: Pressure Relief for High Pressure Separator
Did the RD work well in the application I described? The answer is that it's tolerable. Given a choice, we'd prefer to not have the RD for the reason I mentioned, but it's necessary due to the explosive rate of pressure rise in this application.
RE: Pressure Relief for High Pressure Separator
280 barg and 250 deg C is a bit out of the ordinary but not "first time". I guess that a #2500 would be able to handle this.
The most common reasn for using a RD in series with a PSV is to save money for the materials of the PSV. If you have an agressive medium you can make the RD relatively inexpensive in the right material and use cheap CS for the PSV.
Best regards, Morten
RE: Pressure Relief for High Pressure Separator
RE: Pressure Relief for High Pressure Separator
As I think you've probably gathered, the issue with rupture discs / bursting discs is concern over premature / incorrect operation and the lack of re-sealing and time taken to replace a disc after bursting.
RDs are inherently susceptible to this and the issue of production is not a key issue or concern.
RDs are indicated in some applications as noted either high or low pressure, but the key point will always be about risk, consequence and probability.
If there is a very low probability of an event with a high consequence (rupture / over pressure) then you can accept the limitations of a RD. These include the inability to absorb any over pressure, the perception that these discs weaken over time / fatigue or become corroded and also weaken and the time taken to re-seal after operation. That event would normally need to be something that resulted in a very high pressure compared to the MAWP and / or much higher relief flow rate than would otherwise be required. Some examples are listed above but also low pressure shell side of higher pressure tube heat exchangers often utilise RDs for the unlikely event of a tube failure / rupture.
The more "normal" over pressurisation is dealt with by re-sealing devices.
The addition of a RD usually implies greater margins required between Normal OP, PRV relief set points, RD set point and MAWP / design pressure.
I would think it highly unlikely that a RD would be your only form of pressure relief due to the one time action and consequential down time of the system.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pressure Relief for High Pressure Separator
Thank you very much for the detailed information. I would like to ask a few more questions.
1. Are there a good amount of applications where an overpressurization is expected on a semi-regular basis? I know that a reasonable amount of RD's are used to protect valves from the process media. Can I assume that those applications are not expected to overpressure regularly?
2. Many modern RD's actually perform quite well over many years with no real fatigue issues. Also, as stated above, many are used to protect valves from the process media because they can relatively inexpensively be made from corrosion resistant material. Assuming those two concerns are satisfied, would a resealable rupture disc have any advantages over a traditional PSV for most "normal" over pressurization applications? In other words, are there issues with using PSV's, even for "normal" applications, where the attributes of RD's would help?
3. Your last statement regarding the addition of a RD implies a lower operating ratio for RD's than PSV's. What is the normal operating ratio assumed for a PSV? What is the operating ratio you assume when using a RD?
Thank you again for your time.
RE: Pressure Relief for High Pressure Separator
RE: Pressure Relief for High Pressure Separator
what I meant was that the probability of such an event needed to be borne in mind when deciding what type of relief device to use. Very rare, but high consequence / high flow events could indicate use of a RD, but otherwise some sort of re-sealable device is usually indicated. Any design where a RD was to break on anything less than a 5- 10 year basis would not be thought of as a good thing by operators due to the down time to replace it and re-start the system.
I've heard of but not come across the use of an RD in front of a relief valve or other valve, I suspect their use is relatively rare.
By operating ratio I assume you mean set point accuracy.
A "normal" spring relief is something like - 8 to -10% below set point, with overpressure possible up to 5%
A pilot operated one more like 3%
RD something like 3-5%
All vendor dependant and how much you want to pay.
There is no such thing as a re sealable rupture disc - that's a conflict of terms.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.