Hawkeye122 Posted December 22, 2010 Share Posted December 22, 2010 Can someone please explain how a compressor regulator should be working for my airbrush? My compressor has a pressure gauge indicating tank pressure, I have a regulator and filter connected to the compressor output, and the line out from the regulator goes to my airbrush. The regulator, though, is just a knob that varies the size of an opening in a valve from fully open to fully closed. I can see that this operates as a "flow restrictor" when the airbrush is in use, but the second I release the trigger on the airbrush, doesn't the line pressure equalize with the tank pressure? In other words, if the tank is holding air at 100 psi, and my finger is off the airbrush button, isn't the pressure in the airbrush hose 100 psi, regardless of the regulator setting? It seems this might be stressful to the airbrush and hose, and it seems the first burst of paint must come out of my airbrush at the full 100 psi. This, in fact, seems to be exactly what is happening. What am I missing? Quote Link to post Share on other sites
Don Wheeler Posted December 22, 2010 Share Posted December 22, 2010 If it is just a flow restrictor, you are correct, the airbrush will see full tank pressure when the trigger is up. And, 100psi is probably not good for the airbrush or its hose. With a real regulator, there should be a gauge on the output side showing the pressure it is set to, and it should vary only a pound or two when you press the airbrush trigger. Quote Link to post Share on other sites
dmk0210 Posted December 23, 2010 Share Posted December 23, 2010 (edited) It sounds like you may have a problem with your regulator, or at least don't have it set properly. You should have two gauges, one on just either side of the regulator. The one on the tank side of the regulator shows tank pressure and the other on the airbrush side of the regulator shows the line pressure after the regulator. Tank pressure should always be higher, sometimes much higher (You always set your regulator after your tank has been fully charged.). You should be able to close the regulator completely and have zero pressure in your line even though your tank may have 100psi in it. Disconnect your airbrush from the line and adjust your regulator. Feel the pressure change at the end of the hose as you open and close the regulator. It's just like a water faucet. You have all this pressure in your house plumbing, but you regulate the pressure to your sink or garden hose with the faucet valve(regulator). For example, my compressor will turn on somewhere below 50psi and charge the tank up to about 130 psi then turn off until tank pressure drops below 50psi again. However, I may adjust my regulator to give me a line pressure of 20psi (read on the second gauge). As long as my tank pressure is above 20psi, then my line pressure will be pretty much the same the whole time, even though my tank pressure will vary as it discharges and recharges. ** Now, I say it will stay at 20psi, but I find that I need to press my airbrush button while I set my regulator pressure and it will rise up a few PSI when I let off the airbrush button, so it would be somewhere between 20 and 25psi actually. Lower when I paint and higher when I let off, but always between what I set it and and a few psi higher. I assume this is because I have a cheap regulator. Edited December 23, 2010 by dmk0210 Quote Link to post Share on other sites
Hawkeye122 Posted December 23, 2010 Author Share Posted December 23, 2010 Thank you Don and dmk. I expected it to work as you describe, but it isn't at the moment. I'm using the Paasche R75 regulator, which I think is supposed to be of reasonably good quality, so I must have done something wrong in my setup. I'll check it this weekend. I appreciate your excellent description of how it's supposed to work. Quote Link to post Share on other sites
Spectre711 Posted December 23, 2010 Share Posted December 23, 2010 It should work as you think and not how it is. I have a question about the gauge. I'm looking to pick up a new regulator and have seen some conflicting information about the gauge in this setup. Does it have a 60 or 100 psi max on the gauge and what kind of increments are on it? Quote Link to post Share on other sites
Nick Miller Posted December 23, 2010 Share Posted December 23, 2010 I also have a question about the regulator's pressure gauge. My gauge has a maximum pressure reading of 60 psi. I never go much above 20 psi. I'd like to swap out the gauge with a 0-30 or 0-40 psi gauge. Is there any reason I couldn't just make the swap? Anything to watch out for? Quote Link to post Share on other sites
Don Wheeler Posted December 23, 2010 Share Posted December 23, 2010 Thank you Don and dmk. I expected it to work as you describe, but it isn't at the moment. I'm using the Paasche R75 regulator, which I think is supposed to be of reasonably good quality, so I must have done something wrong in my setup. I'll check it this weekend. I appreciate your excellent description of how it's supposed to work. I wonder if you have it hooked up backwards. You can see the instruction sheet here. Notice that there is a coupler that must be ordered separately. Don Quote Link to post Share on other sites
Spectre711 Posted December 23, 2010 Share Posted December 23, 2010 I also have a question about the regulator's pressure gauge. My gauge has a maximum pressure reading of 60 psi. I never go much above 20 psi. I'd like to swap out the gauge with a 0-30 or 0-40 psi gauge. Is there any reason I couldn't just make the swap? Anything to watch out for? Should be able to just replace the gauge since if do exceed the capacity it would just peg at zero. Quote Link to post Share on other sites
Kei Lau Posted December 23, 2010 Share Posted December 23, 2010 Thank you Don and dmk. I expected it to work as you describe, but it isn't at the moment. I'm using the Paasche R75 regulator, which I think is supposed to be of reasonably good quality, so I must have done something wrong in my setup. I'll check it this weekend. I appreciate your excellent description of how it's supposed to work. The Paasche R75 is a true regulator with a diaphram unit in it. When connect correctly, the gauge measures the output pressure according to the setting of the regulator knob, anywhere from 0 psi and up. The compressor/tank pressure is at the input side of the regulator and you have no way to tell what it is except the gauge at the compressor. If the regulator gauge does not respond to the changing of the knob position, it is not hooked up correctly. The regulator knob has fairly fine resolution and you can easily set the airbrush pressure better than 1 psi accuracy. Some cheapie regulator is just a flow restrictor orfice. They do not work well and the knob is sensitive. You should not have that kind of problem. Quote Link to post Share on other sites
Kei Lau Posted December 23, 2010 Share Posted December 23, 2010 I also have a question about the regulator's pressure gauge. My gauge has a maximum pressure reading of 60 psi. I never go much above 20 psi. I'd like to swap out the gauge with a 0-30 or 0-40 psi gauge. Is there any reason I couldn't just make the swap? Anything to watch out for? Typically, the 60 psi gauge has a "2-psi" grading. It should allow you to set it to within 0.5 psi. In most setup, the gauge reading will fluctuate 1-2 psi between closed and full blast airbrush trigger. It is good enough for any airbrushes. In my setup, I swapped out the gauge to a 2-inches one, but kept the 60-psi full scale. It is easier to read when modeling Quote Link to post Share on other sites
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