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Remote Sensor Pilot Safety Valve

Remote Sensor Pilot Safety Valve

Remote Sensor Pilot Safety Valve

I am evaluating a Revamp project.It requires a 4"x P x 6" safety valve.
The inlet line loss is between 12% to 16% of set at actual valve capacity.
The Client says the next opportunity to increase inlet pipe size will be in the year 2030.
The outlet pipe friction slightly exceeds 50$ of set.
The current view is to install a remote sensor Pilot safety valve.
This would in theory be an adequate design both high friction loss on both inlet & outlet pipe.
Calculations show the orifice size is adequate despite the high losses.

One concern is "good engineering practice".
Just because something "can be done" does not mean "it shall be done"
This is a Safety System and one should hesitate before pushing the limits.
In my conventional view - any inlet loss above 10% of set should have the piping redesigned.

Is there a "percent of set" limit for remote sensor pilot design??

Any comments are appreciated

RE: Remote Sensor Pilot Safety Valve

Selecting a non-modulating pilot-operated safety valve with a remote pressure tap AND the PSV can able handle the required capacity with the lower static pressure at the safety valve inlet nozzle is RAGAGEP.

Total discharge piping pressure drop up to fifty-five percent of the set pressure will not affect compressible flow capacity of pilot-operated pressure relief valves. Why? Because the PSV flow nozzle is choked anyway, so backpressures up to the critical flow pressure in the outlet has no effect.

You have a workable solution that is RAGAGEP and is probably lower cost than piping modifications. Have your calcs peer reviewed. That'll generate some good engineering discussion. Then, go from there.

Good luck,

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

RE: Remote Sensor Pilot Safety Valve


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

RE: Remote Sensor Pilot Safety Valve

In essence though your relief valve is acting now simply as a high pressure on/off valve as it's pressure monitoring function is now somewhere else not impacted by the flow.

I can't see too much wrong with this approach even if it is a little unconventional.

That is a very high back pressure on the outflow pipe though. Can't this be duplicated or made bigger?

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

RE: Remote Sensor Pilot Safety Valve

"Recognized and Generally Accepted Good Engineering Practice" as defined in OSHA's PSM regs.

Good luck,

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

RE: Remote Sensor Pilot Safety Valve

Inlet pressure loss limits are entirely aimed at minimizing the risk of PSV instability (i.e. chatter), by ensuring that the force balance on the PSV is positive (net opening force is greater than the net closing force). [Side Note: We now know that the 3% rule is insufficient for preventing chatter. Other physical phenomena are involved. Ref: API 520 Pt II. But that's another topic.]

Remote sensing pilot valves operate in an entirely different way. Their opening, closing, and mechanical stability is completely unrelated to the inlet pressure loss, because the pilot is only seeing the pressure in the protected vessel (via the remote sensing tube connection to that vessel). For a remote sensing pilot valve, the inlet pressure loss is only affecting the capacity of the valve (by reducing the dP across the orifice). It's important to determine the inlet and outlet pressure losses for these valves, so that the orifice sizing is done based on the dP available to that orifice. Otherwise, the magnitude of the inlet pressure loss is irrelevant - it can be any value.

RE: Remote Sensor Pilot Safety Valve

[b]Message to Latexman, LittleInch, and Don1980
As Gomer Pyle says "Thank You - Thank You - Thank You"

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