Is my PSV over size now?

[Vivaldi M. Smith]

I have a PSV 4"x8" set for 705 PSIG, it is a blocked outlet PSV. The line is a B1 Carbon Steel pipe, with condensate flowing around 15MBPD and at averaqge of 150 PSIG. I am under the impression that the PSV is over sized as the Flow is decreasing exponentially every day. Can this PSV be resized under the actual flow conditions or we have to respect the normal pressure rating of the pipe which is around 740 PSIG.
Please help.

 

[LittleInch]

Only if the flow at blocked outlet is less than you 15,000 BPD figure.

If the max pressure (WHSIP?) is now below 705, then the valve won't lift in any event. So long as nothing else has lowered the MAOP, then I would be tempted to leave it as it is as it is then intrinsically safe, i.e. actual pressure in any event is less than design pressure / MAOP

All these sorts of things need careful review under a written Management of Change (MOC) procedure so that all relevant records and drawings are updated and there are no secondary effects or actions coming out of this. A;lso allows others to consider the impact.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Vivaldi M. Smith]

Replying to LittleInch, The issue is that We are constantly wasting maintenance time on doing ARP on these valves when they are currently serving no realistic purpose. What other options can be put in place if we were to remove the PSV? While is true it is protecting the pipe realistically speaking under current operating conditions they serve no real purpose to take maintenance time.

 

[LittleInch]

What you probably need to do is a comprehensive re-rating exercise to look at the flows and more importantly the max pressures the system can now see.

I'm assuming this is linked to a field so if the WHSIP is now less than your design, then you could easily decide to consider the pipework as intrinsically safe, i.e. you cannot exceed the design pressure ( maybe install a thermal relief), but your big pressure relief valves could be removed and also reset your pressure alarms set points etc.

In essence, you rewrite the design basis for what you know now and then examine the system to see if you can simplify it / remove maintenance heavy equipment which serves no purpose.

Write it all up, get it reviewed and approved and away you go....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Latexman]

I have a PSV 4"x8" set for 705 PSIG

.

Are you sure? 4" x 6" and 6" x 8" are common sizes, but in my experience, 4" x 8" is not common.

the Flow is decreasing exponentially every day.

Can you elaborate on this? I have no oil patch experience.

Good Luck,
Latexman

 

[Vivaldi M. Smith]

You are right Latexman it is actually 4"x6". The plant used to flow around 30MBPD flow is now half .

 

[LittleInch]

It's not uncommon for facilities to be designed for the initial well head pressures / flows and then amended later on as the field becomes depleted and where everything is less than it was at the start.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.