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RELIEF VALVE FOR DIRTY SERVICE

thread408-48975

RELIEF VALVE FOR DIRTY SERVICE

RELIEF VALVE FOR DIRTY SERVICE

(OP)
We have an application that requires a relief valve to be installed on the desalter (17 API crude oil). This PSV will relieve back to the Crude tower which is 200 feet away. I am thinking about locating this PSV at the Crude tower for easy access. However, the inlet drop will be more than 3%. I am thinking about using a pilot PSV but am doubted that it would work for the service. Can I use a remote pilot (like the isodome) at the desalter to control the PSV at the tower? I would appreciate any help for this application.
I am sure some of you have dealt with this issue before. Please share with us your experience.
Thank you very much.

RE: RELIEF VALVE FOR DIRTY SERVICE

Yes, an isodome would work in this service and I've seen it used on a similar crude application.  Most refineries don't like to use pilots in crude service, even non-flowing types because of plugging problems, but the isodome version is a good way around that IF you need a pilot operated PSV.

If the inlet pressure drop is going to be more than 3%, make sure you include that drop in your PSV sizing.

RE: RELIEF VALVE FOR DIRTY SERVICE


As a relief application okay and "do-able" as TD2K suggests, but as a Desalter application, I'd have second thoughts. There is too much junk (salt/water/sand/tars)in  Desalter applications. Be sure to advise your supplier.

Your inlet loss calculation needs to include an allowance for partial blockage due to accumulated sediments, etc. It might be 3% when you first commision it, but not after a few months of service.

RE: RELIEF VALVE FOR DIRTY SERVICE

I'm assuming an isodome provides some type of isolation from the process but I've not heard of that one before.  I did a quick search on the web and it didn't return anything pertinent, does it go by some other name?

Anyway, 200 ft seems an awful long way to run a pilot sensing line.  Think I would be looking for another option.

RE: RELIEF VALVE FOR DIRTY SERVICE

IEA, You may want to look at the possibility of using a non-fragmenting rupture disk on the inlet side of a  relief valve. This keeps the junk out of the valve allowing it to operate when needed. The down side is, every time the valve relieves, it needs to be cleaned and the rupture disc replaced.

We use this setup on dirty services or where operating pressures are close to the valve set-point pressure.

Hope this helps.
saxon

RE: RELIEF VALVE FOR DIRTY SERVICE

FYI, Anderson Greenwood Series 400 Isodome Pilot
may be viewed at the following link:
http://www.crosbyvalves.com/docnet/library/poprvcat.pdf

valve inlet sizes 1-inch through 8-inch
set pressure between 15 and 1480 psig
and continuous service temperatures
from -65°F to +500°F.
• Suited for Dirty or Wet Service.
Non-flowing pilot minimizes entrance
of dirt and formation of hydrates in
pilot. Due to low velocities within the
pilot and supply tubing, most particles
will drop out upstream of pilot inlet
screen. Optional cartridge type pilot filter
is available for extremely dirty
services.

J. Alton Cox
President
DeLuca Test Equipment
www.delucatest,com

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