Problem With Pilot Operated Pressure Reducing Valve

What is the specification of the valve?

The pressure regulators were new? previously used?

brand name? Model number? all the same brand and model

Failure mode ?

manufacturer's assessment?

If this valve is similar to what I am used to in the fuel industry it works by applying pressure to the top of a valve pinching it closed when excessive pressure is sensed downstream. This pressure is applied through a pressure relief valve downstream set at your fixed pressure (19 bar). If the pressure relief valve opens it sends it's excessive pressure to the top of the control valve reducing flow or pressure.

This is balanced by another relief valve that applies pressure to the bottom of the control valve if there is a pressure drop downstream of the control valve.

Common problems in this system is leaky valve seats allowing pressure to bypass any of the pressure relief valves or the main control valve itself. Also, if the pressure relief valve that pinches down the control valve does not operate quickly enough or is set for the wrong pressure you will have problems.

Hope this helps.

Drew

You may have dirt or compressor oil in your lines. Do you have a drop leg and strainer ahead of this valve?

Hi All, Thanks for your comments so far. I regret I am unable to answer some of your queries due to the fact that I've been unable to access the technical documentation. What I can confirm is that in all cases, the regulators used were new. Also, installation was done by a third party and so the manufacturer's assessment is unavailable. Furthermore, there is no, strainer or drop leg installed. Upon opening the pilot filter, a high level of debris were observed. Even though this was cleaned, the result was the same. On the basis of some of the answers I have received, I would like to ask, are we justified in using a pilot valve(given that the gas stream has a lot of particulate material), or would we be better off using a pneumatic controlled valve.

For This type of pressure sensitive system it would be best to continue with the pilot operated regulator. A sugestion would be to install an inline strainer prior to the regulators.. The fuel gas is always dirty. Have the operators to blow down the filters on a regular basis. The existing regulators would need to be cleaned internally because the gunk in the fuel gas is sticky and therefore the pilot regulators get sticky.

You must understand the failure parameters. you cannot repair it when you don't know what to repair. There are a lot of possibilities: dirt, abrasion, damaged diaphragms and of course, the PCV may not be adequate for the job...

What would be the comparative advantage/disadvantage, if we decided to use a pressure control valve actuated by instrument air, rather that the current arrangement with the pilot valve where the actuation is by means of the fuel gas stream itself. (from an engineering and economic sense)

This is the only setup that I wopuld allow on my site.

As what I originally suggested appears to be the main cause of the problem, and as the problem you describe is a hazardous condition, I would further suggest that you have the recommended equipment installed as soon as possible, regardless of what type of pressure/flow control you choose.

If the fuel is gaseous (cng) then your best bet is to use a pressure reducing regulator set to 19 bar outlet. Contact Neil @ 519 496 9755 (BALCKSTONE POWER) HE IS AN EXPERT IN THIS AREA WITH OVER 30 YEARS EXPERIENCE.