Reactor Pressure Relief
Reactor Pressure Relief
(OP)
Anyone have any thoughts on the appropriate relief of a reactor that has two phases of operation. Phase 1 (Mixing) , small rupture disk at a high pressure (below rating of vessel). Phase 2 (Reaction) is where I need to relieve the reactor at a lower pressure to keep the size of the rupture disc small. Does anyone have experience with switching out rupture discs on a reactor based on the phase of a batch.





RE: Reactor Pressure Relief
What if the wrong disc is put in at the wrong stage?
What if someone forgets to change a disc over?
What about hazards due to exposure when changing the disc over?
Size your relief vent for the worst case scenario, and set the set pressure to that required (Usually design pressure of vessel) and leave it at that. If your vent is too small for the worst case, make it bigger. Anything else is unsafe.
RE: Reactor Pressure Relief
A point not mentioned is that rupture disks don't like to be handled. One small scratch or dent can seriously affect the bursting pressure, that's why they come in nice boxes.
We run a highly reactive continuous process where we have "dump/vent valves" that are triggered by different process anomalies that will vent/dump the units contents to hopefully quench the process way before the PSV's come into play.
If there is an process excursion that would require the PSV's to operate the dump valves will come into play as the pressure increases to relief pressure.
RE: Reactor Pressure Relief
RE: Reactor Pressure Relief
Explain to us why you need to dump the reaction phase at a lower pressure? Does it have to do with the design temperature of the vessel?
StoneCold
RE: Reactor Pressure Relief
RE: Reactor Pressure Relief
The primary sysytem (PAHH) could fail. Remember to put a PAHH on a seperate instrumten (not you nomal pressure indicatior) since the reason for the process getting out of hand could be a false reading from this instrument!
Best regards
Morten
RE: Reactor Pressure Relief
I am not following you about a higher reactor pressure requiring a larger dump valve. Increasing the reactor pressure should decrease the dump valve size. Unless you are worried about the rate of reaction being faster so you think you should dump the reactor faster.
We don't have dump valves but we do have batch reactors with rupture disks and we do everything we can to avert a relieving event. Having a higher rupture disk pressure increases our time to react, and in most instances allows enough time for the limiting reagent to run out or cooling to bring the reactor back under control. If it was my unit I would set the rupture disk as high as possible (less than or equal to MAWP) and leave it there. I would set the dump valve at a lower pressure but still comforably above the highest normal operating pressure. Then you are always covered and you are not relying on changing the rupture disk to save you. Because unless you have very stringent documentation, and signoffs by people who are willing to take responsibility you are going to have an accident.
RE: Reactor Pressure Relief
RE: Reactor Pressure Relief
just my two cents,
chris
RE: Reactor Pressure Relief
DO NOT design a safety system that requires human intervention for it to operate properly, i.e. switching rupture discs depending on mode of operation. Design the pressure relief system for the worst case scenario. Then use pressure controls or dump valves to limit maximum pressure for each operating mode. If the controls fail, the pressure relief will save you no matter what operation mode you are in. Trying to save pennies on a safety system, can cost you big bucks in court.
Just my humble opinion!
ProcessDr
RE: Reactor Pressure Relief
This is the same concept (SIS) that is used at our site. The original system was controlled by Provox but more of the control is being offloaded to local DSP’s with over site by Provox.
SIS (Safety Instrumented Systems).
Check out the FieldView pdf
http://ww
http://www.emersonprocess.com/sis/index.html