Ask the Expert Question-and-Answer Archive

by Ron Joseph

July, 2004

Setting Up HVLP Spray Gun for Compliance

Q. Each gun is different and seems to have its own apparatus to be used to measure the air pressure at the paint gun cap and determine if it meets the EPA's definition of an HVLP gun (i.e., air pressure of 10 psi or less at the cap).

Question #1: Is there a standard operating procedure on how to perform this test? There does not seem to be any manufacturer's data suggesting how exactly the test is to be performed to insure an accurate result. Most just state that you need to set up the spray system and then remove your usual cap and place test cap on the gun.

Question #2: Do you spray paint through the nozzle when performing this test or are you supposed to measure the pressure with no paint for atomization?

A. You are correct in stating that there is no standard procedure for measuring the atomizing air pressure at the cap of an HVLP spray gun. Perhaps the South Coast AQMD. has such a procedure, but I have not seen it.

This is the procedure that I follow: I ask a painter to set up a spray gun exactly as if he were to spray paint at that particular time. Once he has established his fluid pressure, atomizing air pressure and fan size I then asked him to remove his working cap and replace it with the test cap. When he pulls the trigger of the HVLP sprayer the pressure gauge must read less than 10 psig otherwise he is in violation of the regulation.

If you would like to set up a procedure for your shop you might have painters setup their spray guns for a typical painting operation at Gulfstream. After they have set up the guns and are ready to do the job that is the time to replace the working cap with the test can.

If an inspector were to visit your facility bear in mind that in all probability he/she has no idea how the procedure should be performed, but if you show him/her the method you use I expect that the inspector will be quite happy.

The most important thing is for your painters to know that an HVLP spray gun can easily be out of compliance and that the painters must take special care not to turn up the atomizing air pressure too high.

When you test the pressure reading you are not obligated to spray paint through the nozzle, but if I were an inspector I would want to be absolutely sure that you have set up the gun as if you were going to spray the paint.

I hope this answers your questions.

Best wishes,

Ron Joseph