Pressure Regulators with Diaphragms

Feb 15, 2008

Problems with Pressure Regulators
by: Bill - Publisher

Larry, nice hearing from you.

Most general purpose regulators are diaphragm type, with a spring over the diaphragm. This spring gets compressed or relaxed in reaction to set point of the regulator and the fluctuating air pressure coming from upstream.

There's a lot of information about air regulators on this page.

The vast majority of compressed air regulators are "relieving" rather than "non-relieving". This means that if there's ever an increase in downstream pressure for any reason, and that pressure increase exceeds the pressure setting of the regulator, then that over-pressure will bleed back to atmosphere through the hole in the top of the "relieving" regulator body.

A "non-relieving" pressure regulator is used where the gas or liquid being regulated is noxious; hazardous to people or the environment, and that stuff you don't want to escape to atmosphere from the regulator.

If your regulator is bleeding air continuously from the bleed hole, and there's no reason why there would be any back pressure to the regulator from any downstream operation, then it's likely that the internal diaphragm has developed a hole, allowing air to reach the bleed hole inappropriately.

If it's intermittent, your diaphragm likely does not have a hole, and it's back pressure from downstream causing the bleed.

In terms of regulator overall operation, a general purpose regulator and gauge will hold a pressure to within plus or minus 3-5 PSI of the set point. When you set your regulator to your set point, does the gauge show the downstream pressure that you've selected? If it does, then that's one check that the regulator is working OK.

The other check is how quickly the regulator responds to change in downstream air pressure. If you have a sudden pressure drop downstream, for example, an air cylinder cycles or the trigger on an air-brush gun has been depressed, you should see a downward blip in the regulator gage, that corrects back to the pressure set point almost immediately when the downstream air use stops.

That's assuming that your compressor has enough capacity to recharge the tank, or that the tank has enough air to fill the line to the regulator quickly enough.

I hope this helps. Add a comment if you have any more questions or if I haven't been clear enough.

Cheers,

Bill

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Feb 15, 2008
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Submitted by: Bill - Publisher

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Larry, nice hearing from you. Most general purpose regulators are diaphragm type, with a spring over the diaphragm. This spring gets compressed or relaxed in reaction to set point of the regulator and the fluctuating air pressure coming from upstream. There's a lot of information about air regulators <a target=ÃƒÆ’Ã†â€™Ãƒâ€šÃ‚Â¢ÃƒÆ’Ã‚Â¢ÃƒÂ¢Ã¢â€šÂ¬Ã…Â¡Ãƒâ€šÃ‚Â¬ÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€šÃ‚ÂblankÃƒÆ’Ã†â€™Ãƒâ€šÃ‚Â¢ÃƒÆ’Ã‚Â¢ÃƒÂ¢Ã¢â€šÂ¬Ã…Â¡Ãƒâ€šÃ‚Â¬ÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€šÃ‚Â href="http://www.about-air-compressors.com/regulators.html"> on this page. </a> The vast majority of compressed air regulators are "relieving" rather than "non-relieving". This means that if there's ever an increase in downstream pressure for any reason, and that pressure increase exceeds the pressure setting of the regulator, then that over-pressure will bleed back to atmosphere through the hole in the top of the "relieving" regulator body. A "non-relieving" pressure regulator is used where the gas or liquid being regulated is noxious; hazardous to people or the environment, and that stuff you don't want to escape to atmosphere from the regulator. If your regulator is bleeding air continuously from the bleed hole, and there's no reason why there would be any back pressure to the regulator from any downstream operation, then it's likely that the internal diaphragm has developed a hole, allowing air to reach the bleed hole inappropriately. If it's intermittent, your diaphragm likely does not have a hole, and it's back pressure from downstream causing the bleed. In terms of regulator overall operation, a general purpose regulator and gauge will hold a pressure to within plus or minus 3-5 PSI of the set point. When you set your regulator to your set point, does the gauge show the downstream pressure that you've selected? If it does, then that's one check that the regulator is working OK. The other check is how quickly the regulator responds to change in downstream air pressure. If you have a sudden pressure drop downstream, for example, an air cylinder cycles or the trigger on an air-brush gun has been depressed, you should see a downward blip in the regulator gage, that corrects back to the pressure set point almost immediately when the downstream air use stops. That's assuming that your compressor has enough capacity to recharge the tank, or that the tank has enough air to fill the line to the regulator quickly enough. I hope this helps. Add a comment if you have any more questions or if I haven't been clear enough. Cheers, Bill

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