Overpressure protection of HC liquid cartiridge filters and HC-wtaer liquid coalescers

[adt10]

Would appreciate very much any feedback on overpressure protection design for hydrocarbon liquid cartridge filters and hydrocarbon-water liquid coalescers. I am working on a system which has a cartridge filter located upstream of the coalescer to filter out any solids to prevent plugging of the coalescing element. To prevent over pressuring during external fire how many PSVs (pressure safety valves) should be installed on each vessel - one (1) on each side of the filter cartridge and coalescing element or just one (1) upstream of the elements? It seems the safer design would be to install two (2) PSVs on each vessel. If only one (1) PSV located upstream of the filter or coalescing element is used the downstream section without the relief valve may be over pressured because of possibly high pressure drop thru the element. Also, there is a possibility of filter cartridge being plugged. Would like to know about some actual design and what is the industry practice. Thanks.

 

[e43u8]

adt10,

Please upload a simple sketch of the system you described included the valves. It can help to submit better response to your query...

 

[sshep]

Adt10,
A psv on each is best. A common psv is a cheaper design which puts administrative burden on operations.
Best wishes,
Sshep

 

[adt10]

Thanks e43u8 and sshep for responding. Attached is the sketch requested by e43u8.

sshep: Did you mean a PSV on each vessel or each side of the vessel which would mean 2 PSVs on each vessel? Also, I did not understand the "administrative burden on operations" if one (1) PSV is used. Will one(1) PSV require more frequent inspections? Could you please clarify that comment. Thanks.

 

[adt10]

Last time the attachment operation was not completed.

 

[GHartmann]

It appears to me that you have located the PSV's correctly.

One on each vessel, upstream the internal elements.

There is no need for the second PSV on each vessel.

However, the 1.5 x 2 relief valve does seem small for the fire case

 

[e43u8]

adt10,

What is your problem with current configuration? Because there are manual isolation valves between filter and coalescer, both equipment can't be protected with one PSV. Indeed, provision of the spare for PSV isn't mandatory per API and ASME Sec. VIII, then appears current configuration to be acceptable. With the limited info you are provided seems credible scenarios are blocked outlet and fire case, and if only fire case is credible scenario it's not unusual to install one PSV on the equipment is to be protected and the spare PSV to be kept in warehouse in saving standpoint...

 

[sshep]

You only need one PSV per coalescer. It looks fine.

 

[adt10]

Thanks to every one for your comments. For the filter our concern was that the part of the vessel downstream of the filter cartridges would not be protected by the PSV located on the part upstream of the cartridges because the cartridges may be plugged or pressure drop thru the cartridges would be too high. To alleviate this concern we plan to connect the PSV to both sides of the vessel - upstream and downstream of the cartridges. After finding out the details of the coalescer we have realized that the internal configuration is different from the filter and there is no concern like the filter.

 

[e43u8]

adt10,

No need to connect the PSV to downstream side of the cartridge at all, because the source of over pressure is at upstream side of the cartridge...