Pressure control resolution 4

[rollingcloud]

This is for pressure testing on a pressure relief valve. The aim is to adjust the inlet pressure from 0.00 to 150.00 psig. However, we are experiencing jumps in the pressure readings, typically in increments of 5-10 psig—for example, jumping directly from 110 to 120 psig. Ideally, the pressure should increase in finer increments, like 111, 112, 113, etc. Our testing setup, as designed by a previous engineer, utilizes the TESCOM 44-1800 series. This regulator is capable of handling a maximum inlet pressure of 6000 psig and an outlet pressure range of 0-2500 psig. Since we are only operating within a 0–150 psig range, the 0-2500 psig capability appears to be excessive to me. Perhaps a regulator of the same type but designed for a lower pressure range would provide better resolution/control?

The current setup from our supplier includes a pressure regulator on top of the tank and a needle valve before the inlet. However, this arrangement is resulting in pressure jumps of 5-10 psig during testing when the operator adjusts the pressure regulator's knob.

 

[rollingcloud]

Yea, it looks like I don't need the venting option for testing closing & opening pressures, but when testing leakages, for example, internal leakage, port B is connected to a flow meter and port C is blanked, when closing pressure is reached, port A is also blocked, flow leaks to port B and the flow meter measures the leakage. I believe in this case the outlet pressure of the regulator would experience high built-up pressure since most of the gas has nowhere to go, venting might help in this case?

 

[Prometheus21]

If I'm understanding the setup correctly then yes, a vent would indeed help for that last testing part (and, thinking about it, the cost of adding it in the Swagelok regulator is most likely smaller compared to other solutions)

It's an interesting setup, feel free to update this thread in the future with your results.

 

[rollingcloud]

Just to clarify, the sketches describe how the valve function after the actual installation in the field, where the port B connects to a regulator during its entire service life.
During testing, port A is connected to the pressure regulator (the one that I am trying to buy). Just want to make sure I am not misleading.

There was a phenomenon that's confusing me. During the internal leakage test, when port C is blanked and then P1 is supplied, the duct to the flow meter experienced an abnormal amount of built-up pressure to the point that it disconnected itself at the port with a loud 'poof' sound, which scared the heck out of me. However, if we supply the pressure above the closing pressure first and then blank port C, everything is fine, and the flow meter measured a normal amount of leakage too. It would make sense to me if both cases caused the duct to disconnect with a loud 'poof' sound, because in either scenario, the gas has nowhere to go.

It might have something to do with the valve being initially open, which allows the gas to flow into the flowmeter freely, quickly building up pressure in the duct. In the second scenario, where port C is blanked after the valve is closed (and port A is blocked), only a small amount of gas leaks through port B to the flow meter, which is why it does not experience a high build-up of pressure. This is the only reason I can think of.