thePetroStreet

the prv of the column is passing slightly,we identifyed the passing through thermography and process upset, is there any solution to arrest the passing, service is hydrocarbon,pressure is less than one kg/cm2,prv is poilet operated, and there is no isolation valve on the upstream and downstream.prv is directly connected to flare line. please give some suggestions.

thanks and regards,
karthik,

The one way of stopping PRV is to increase the set pressure within the safe margin of equipment design pressure. I would like to know which thermography(Model and make) you have used to monitor the PRV.

Field adjustment is the right option. But before doing that you must consult the manufacturer, they always have a set procedure of performing field adjustment. We did the same at our site some three four times but after seeking manufacturer's recommendations.

Do take appropriate safety measures while performing online field adjustment activity.
And one more thing, even with field adjustment it is not sure that the passing of PRV will stop once for all. During any shutdown window bring the PRV to shops and fix the actual problem on test bench.
Anyway, take your chance with field adjustment and let's see.

Many of the manufacturers for Pilot operated PRVs specifically mention that no field adjustment (in service adjustment) shall be made on PRV until or unless it is isolated from the pressure source. It is highly likely that PRV may open up inadvertently resulting in any serious injury or system malfunctioning.
We have many PRVs operating manuals with this warning clearly written.
The best way to go is to consult the manufacturer before you decide anything about it. Normally, if they allow you they also mention the step by step procedure for the same.

We did same kind of job at our Urea Plant some 2 years back when a PSV downstream of scrubber was leaking.
1. Field adjustment was done by bringing the inlet pressure to 75% of PSV set pressure.
2. Set pressure was increased by 5% after taking approval from Process guys.
3. Manufacturer suggested not to undertake this safety critical job as it may or may not stop the leakage but they did mention the amount of adjustment to be made to increase the set pressure by 5%.
4. Adjustment screw was moved to a quarter turn and the leakage was rectified.
5. Soon after less than 02 months, it started leaking again.
6. Complete rectification was done by bringing in the PSV to workshops and lapping job was done on the seating area.