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Michael O'Sullivan
09-20-2008, 7:42 PM
When you read the regulator to find out what pressure (psi) you are at, which is the correct value: the value when the trigger is not depressed, or when it is?
Tom Veatch
09-20-2008, 8:23 PM
When you read the regulator to find out what pressure (psi) you are at, which is the correct value: the value when the trigger is not depressed, or when it is?

The static pressure reading with no flow (trigger not depressed) is pretty useless, IMO. With the trigger depressed, and air is flowing, the gauge is showing the pressure at (or near) the outlet of the regulator/inlet of the hose and is a more accurate indication of the actual air pressure in the hose.

Assuming the gauge is upstream of the hose, the pressure at the hose outlet/tool inlet will be somewhat less than the regulator gauge reading because of pressure losses in the hose (pressure loss through the hose is directly related to flow rate and hose length and inversely related to hose diameter)
Michael O'Sullivan
09-20-2008, 8:40 PM
Tom-

Thanks -- that is what I thought. I actually have two regulators -- one that is attached to the compressor, and one that I have at the end of the hose, to which I attach whatever I am using. I use the latter to judge the pressure.
Anthony Whitesell
09-20-2008, 9:31 PM
That would depend on if the regulator is designed to read static or dynamic pressure. Most are designed to read static pressure (the dynamic pressure gauges are much more expensive).

The regulator should be set based on the static reading, without the trigger pressed. If the regulator is set dynamically, when the flow is stopped there may be an unacceptable, possibly dangerous, pressure in the line.

The better setup is what you already have; two regulators. With one on the supply to ensure that the lines are not over pressurized and a second at the attachment to control the actual feed pressure to the equipment.

If you set the pressure dynamically you risk damaging the equipment due to the higher static pressure. Pneumatic equipment is designed to handle static pressures, not dynamic.