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Pressure Relief catch tank

Pressure Relief catch tank

(OP)
thread1203-250431: Pressure Relief catch tank

I'm bumping this thread up asking if there is a code requirement for sizing of a relief catch tank. Client (Pharma) has several reactors (toluene, solvents). Each has a rupture disc with vent line. All vent lines are connected to one relief catch tank, to capture the "moisture" out of the fumes in case of a runaway reaction triggering the rupture disk. Catch tank is atmospheric and vented to atmosphere.

I'm looking for sizing guidance for this tank. Code requirement if there is one. 1.5 - 2 x volume of largest reactor, yes?
In ideal conditions, the catch tank is empty. Would there be an occupancy classification applicable?

On a side note: client has installed his catch tank on the parking lot. That seems odd to me...

Thank you!

I design aqueducts in a parallel universe.

RE: Pressure Relief catch tank

Relief system KOD in a parking lot - that sounds as bad as BP having contractors with their portacabins parked in the flare drum sterile zone in the Texas City refinery disaster.

Though API 520 is mainly for hydrocarbon plants, there is a great deal of guidance you'd find here for this application. Also ask process safety engineers to run a thorough review of the hazardous area classification of this KOD location, and run the mandatory vent dispersion and radiation calcs also. A HAZOP study, lead by a qualified HAZOP leader would then be most likely required by legislation for your location.

RE: Pressure Relief catch tank

(OP)
Thanks. Review and Hazop is actually what my firm has been asked to do. I was asked to look into the catch tank, sizing requirements, etc. I'll see if I can find API 520.

I design aqueducts in a parallel universe.

RE: Pressure Relief catch tank

When you visit the plant, park away from that tank. Far, far away!

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

RE: Pressure Relief catch tank

(OP)
API 521 is where I found some good info.

As for visiting the plant, my manager will go. 2thumbsup

I design aqueducts in a parallel universe.

RE: Pressure Relief catch tank

The API recommended 30minutes retention time for liquid reliefs in the vent KOD between NLL and LAHH may be relaxed to 5-10minutes, in my experience, if all of the following are valid:
a) Redundant level transmitters at vent KOD for level detection and trip
b) KOD levels are monitored at CCR and the CCR is continously manned
c) Plant operators at CCR are trained to respond quickly to activate required shutdown measures in the event the plant safety system doesnt activate auto shutdown sequence on LAHH for some reason or other.

It also requires the plant owners written approval to go for this reduced retention time.

RE: Pressure Relief catch tank

A second on using methodology in API 521. Also, if you have it, refer to the program that comes with CCPS "Guidelines for Pressure Relief". There is a program included which allows for very fast calculation of a V/L separation system.

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