Paint Spray Guns

Non-Electrostatic

SPRAY GUNS: AIR VOLUME AND HOSE SIZE

Q: If you have the same constant pressure on the spray booth regulator, why does the hose size matter when using an HVLP gun?

A: The pressure at the regulator on the wall of the spray booth might remain constant, especially if the regulator does its job.  However, the pressure at the handle of the spray gun will depend on the length of the hose, its diameter, the number of fittings between the regulator and the handle, the flow rate of the air (measured in cubic feet per minute (cfm)), and the resistance of the HVLP gun itself.  If you can get sufficient compressed air to the gun when you use a small diameter 1/4" hose, such that the air can properly atomize the coating, then you don’t need a larger diameter hose.  However, in many cases the pressure at the handle is not adequate to provide acceptable finishes.  In such cases you need to take steps to bring more air to the gun.  The easiest method is to use a 3/8" hose.  Other steps are to remove unnecessary quick disconnects, regulators, small diameter fittings, etc.

Most HVLP spray gun vendors suggest that if you require a hose 25 ft or longer, you should insure that is is 3/8" diameter.

Q:  What if the hose length is NOT long (less than 25 ft.) can you still use a 1/4" hose?

A: Yes, if you are satisfied that you are getting sufficient air to the gun you can keep your 1/4"hose.  Remember, the criterion is not the size of the hose, or the air pressure, but rather the volume of air that passes through the HVLP spray gun to atomize the coating.  Since we don’t have an inexpensive instrument for measuring the volume, we reply on the pressure reading.  The ultimate decision therefore depends on your being able to produce a finish free of “orange peel”. 

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