Why is my pressure regulator drifting down?

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Discussion Overview

The discussion revolves around the issue of a pressure regulator drifting down in a system using gaseous nitrogen (GN2). Participants explore potential causes for the observed decline in downstream pressure, despite the expectation of stability in a non-flowing system.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes experiencing a steady decline in downstream pressure at a rate of ~50 psi/hour after a period of stability, raising questions about the regulator's performance.
  • Another participant suggests that condensate accumulation could be causing a clog in the vent port, although they express uncertainty about how this would relate to the observed pressure behavior.
  • A participant confirms that the gas in question is GN2 (gaseous nitrogen), clarifying the type of gas involved in the system.
  • One suggestion is to check if the gas is warm before reaching the regulator, as thermal contraction might be affecting the regulator's performance due to cooling gas.
  • A participant raises the possibility of a fault with the downstream gauge or transducer, noting that gauge leaks can lead to misleading pressure readings.

Areas of Agreement / Disagreement

Participants express differing views on the potential causes of the pressure drift, with no consensus reached on the underlying issue. Multiple competing hypotheses are presented, including thermal effects, gauge faults, and condensate accumulation.

Contextual Notes

Some assumptions about the system's conditions, such as the temperature of the gas and the integrity of the gauge, remain unresolved. The discussion does not clarify the specific nature of the environment affecting the regulator.

Who May Find This Useful

This discussion may be of interest to individuals working with pressure regulators, particularly in systems involving gaseous nitrogen or similar applications, as well as those troubleshooting pressure measurement issues.

steves1080
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I have a self-venting single-stage pressure-reducing regulator that takes ~2500 psig and steps it down to ~1500 psig (here is a link with the specific details of the hardware if interested: http://www.items.se/Dokument/44-1300_10061107.PDF). I experienced some odd behavior recently where the pressure transducer in the downstream process piping began a steady decline at ~50 psi/hour after remaining stable for ~3 hours. This pressure should be stable since the GN2 sitting in this line should be static (nothing is actually flowing during this time). I cannot seem to explain why this is occurring. Upstream of the regulator, pressure is being supplied to multiple other locations where it does continuously flow. Any insight as to what is occurring would be greatly appreciated.

Thanks
 
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A fellow coworker seems to think that condensate is accumulating and causing the vent port to become clogged, but that would only sort of make sense to me if the outlet pressure was rising. This reg is located in an enclosed panel in an outdoor environment. It is not uncommon for there to be condensation on the pipes in this panel.
 
It's air or steam or what?
 
It's GN2
 
steves1080 said:
It's GN2
Gaseous Nitrogen I presume.
 
Correct
 
I would check your gas is warm before getting to the regulator. It might be thermal contraction as the gas cools the regulator - or cold gas upstream is cooling the regulator via the pipes.

Wouldn't worry about water (ice) inside as nitrogen gas contains very little of it.
 
How do you know that it is not a fault with the downstream gauge or transducer ?
I have seen that sort of thing happen when a gauge leaks and builds up pressure on the back of the gauge.
Can you exchange test the gauge ?
 

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