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Your ways to measure lockup pressure of the pressure regulator in wide open upstream monitor system.

Dear community,

could you please share your methods to measure lockup pressure of the regulator in wide open upstream monitor system.

Please notice that after closing block valve on downstream, what you actually see on downstream manometer is locking pressure of the monitor (monitor's pilot).

It is caused by monitor's pilot exhaust connected to the downstream. If you are not able to measure right lockup pressure of the regulator, how to diagnose regulator valve seat without dissasembling.

Let's discuss about it on MFL example pressure regulator.

Best regards

MSc Artur Imiołczyk

Natural Gas Engineer

6 Replies

  • Artur,

    You are correct in that the simplest way to verify and measure the lockup pressure of the regulator in the wide open monitor system is to close the block valve downstream. If both regulators are properly working the downstream manometer will record the lockup pressure of the pilot on the monitor. If there is continued pressure rise downstream higher than the lockup pressure of the monitors pilot, then it is an indication that something is not operating correctly in the monitor system. This could be any of three leak paths, the main valve, the monitor pilot, or the main valves pilot.

    The easiest way to determine if the continued pressure rise downstream is caused by either of the regulators having a damaged seat or if it is damage in the pilots is to isolate the inlet pressure line of the pilots. Once this is isolated, the pilots will gradually bleed the trapped pressure downstream and allow both the monitor and the main valve to close.

    Once both pilots are isolated and the downstream block valve is closed the pressure downstream and the intermediate pressure between the monitor and main regulator can be observed. If the intermediate pressure continues to rise the issue is likely to be with the monitor regulators seat. If the higher intermediate pressure leaks into the downstream area the issue is most likely with the main regulators seat.

    If the intermediate pressure and downstream pressure remain constant with the pilots isolated the damage is most likely located within one of the pilots. The inlet pressure line for the monitors pilot can be opened first. If the downstream pressure continues to climb after the downstream pressure has met the monitor pilot set point then the damage is likely within the monitor pilot. If the pressure stabilizes and does not continue to rise once the pressure has met the monitor pilot set point your damage is likely within the regulator pilot.

    Best regards,

    Morgan Cummings | Application Engineer | Pressure Management

    Emerson Automation Solutions

  • In reply to Morgan Cummings:

    Morgan,

    Thank you for response.

    Note, that by closing block valve on downstream there is no possibility to determine if main regulator valve is sealed. After lockup pressure of the monitor's pilot being reached the monitor is close. If monitor's valve is sealed there is no pressure rise on downstream even if main regulator valve is not sealed.

    This test method also will fail in determining if monitor's valve is seal.  In case if  two valves (monitor's & main regulator's) are untight we can observe pressure raise on downstream.

    Standard gas pressure line is equiped with single pressure gauge on downstream and with most cases there is no intermediate measuring point between monitor and main regulator in wide open monitor system.  

    Theoretically we can test separately monitor's and main regulator's valve in below cases :

    - main regulator's valve test, by opening monitor valve and closing monitor's pilot exhaust line,

    - monitor's valve test, by opening main regulator valve and closing main regulator's pilot exhaust line.

    Best regards

    MSc Artur Imiołczyk

    Natural Gas Engineer

  • In reply to Artur Imiolczyk:

    Artur,

    You are correct that theoretically on most pilot operated monitoring systems closing the pilot sense/bleed line will close the regulator and allow you to easily test the lockup of the main valves independently. The design of the MFL limits the effectiveness of this procedure as the downstream pressure above the diaphragm isn’t directly connected to the sense/bleed line of the pilot as is traditionally done with other pilot operated regulators. As these pressure chambers are not connected via the sense/bleed line closing the pilot sense/bleed line does not guaranty the equalization of pressure above and below the diaphragm that other pilot operated regulators use in conjunction with the spring closed mechanism of the main valve to close.

    I believe a modification of the testing procedure I provided before will offer you a simple field test for the main valves utilizing only your downstream gauge.

    Testing station lockup

    Close the downstream block valve. As the pressure rises the main valve and pilot will shut first followed by the upstream wide open monitor and its pilot. If the pressure downstream of the monitor assembly continues to rise past the lockup of the monitors pilot either the pilots or main valve are allowing leakage.

    Testing the pilots

    If the pressure continues to rise after the main block valve is closed the pilots can be determined if they are the leak path by isolating the sense/bleed lines. Best practice is to isolate the pilots one at a time and observe if the pressure continues to climb. If the pressure rise is stopped by isolating one of the pilots the leak path is within that pilot and troubleshooting efforts should be focused on that unit.

    Testing the upstream monitor

    With the downstream block valve open if you isolate the inlet to the pilot of the upstream wide open monitor and allow the valve to cycle closed as the remaining pressure bleeds downstream the main regulator will remain fully open. Once this pressure has dropped below the worker setpoint you can isolate the downstream block valve and the sense/bleed line on the main valve. This will leave the only leak path as the monitors main valve. If the pressure continues to rise the seat of the monitor valve should be examined.

    Testing the main regulator

    With the downstream block valve open if you isolate the inlet to the pilot of the main valves pilot and allow the valve to cycle closed as the remaining pressure bleeds downstream the upstream monitor will remain fully open. Once the downstream pressure has dropped measurably you can isolate the downstream block valve and the sense/bleed line on the upstream monitor pilot. This will leave the only leak path as the main valve. If the pressure continues to rise downstream the seat of the main valve should be examined.

    Best regards,

    Morgan Cummings | Application Engineer | Pressure Management

    Emerson Automation Solutions

  • In reply to Morgan Cummings:

    Morgan,

    you have written :

    "Testing the upstream monitor

    With the downstream block valve open if you isolate the inlet to the pilot of the upstream wide open monitor and allow the valve to cycle closed as the remaining pressure bleeds downstream the main regulator will remain fully open. Once this pressure has dropped below the worker setpoint you can isolate the downstream block valve and the sense/bleed line on the main valve. This will leave the only leak path as the monitors main valve. If the pressure continues to rise the seat of the monitor valve should be examined."

    Could you confirm that with open valve on feed line to the pilot, closing the valve on pilot control/exhaust line will not cause closing the main valve.

    Best regards

    MSc Artur Imiołczyk

    Natural Gas Engineer

  • In reply to Morgan Cummings:

    Update 02.09.2019 : I would like to consult solution similar you have introduced but with no valve on feed line to the pilots. Could you please answer the question posted 26.08 ?
  • In reply to Artur Imiolczyk:

    Artur,

    In the scenario described for testing the monitors main valve.

    The inlet to the monitors pilot is closed which will close the monitors main valve and prevent any downstream leakage from the monitors pilot.

    Once this is done the inlet to the workers pilot is left open and the bleed/sense line for the workers pilot is closed. Once the bleed/sense line for the worker is closed the downstream block valve can be closed.

    The loading pressure shown in blue on the main valve will begin to bleed into the sense line but due to the small volume it will not fully exhaust keeping the workers main valve slightly open thus not completely shutting off.

    Once these steps are completed any downstream increase in pressure before the main block valve observed will be due to leakage past the monitors main valve seat. We recommend this test procedure for this specific regulator monitor train, to test the Monitor’s Main Valve’s seals for tight shutoff.

    Due to the complexity of this inquiry I believe we can better provide value taking this offline. It’s getting a bit complicated for the purpose of this EE365 discussion.

    Let discuss in more detail. You can reach me by emailing TechSupport.Regulators@Emerson.com