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ADJUSTING FOR AIR LINE PRESSURE DROP AT THE GUN

We have mentioned air line pressure drop, as well as dynamic air pressure readings when previously discussing spray gun air atomizing settings. Air line pressure loss occurs throughout the shop, and insufficient hose size and quick disconnects are the main culprits.

Ideally we want the incoming air pressure to our spray gun or air tool at the recommended operating pressure so we have to factor in an allowance for pressure loss due to the length of airline travel. Air line pressure drop is effected by; length of travel, CFM, and air pressure at the source. The chart below illustrates the pressure drop in a 35 ft. hose at various CFM’s and output air pressure.

Pressure Drop in 35' rubber hose
(not including pressure drop from fittings & Q. D.)

6 cfm @

10 cfm @

15 cfm @

Hose I.D.

125 psi

30 psi

125 psi

30 psi

125 psi

30 psi

1/4"

5

15.7

12

N/A

26.8

N/A

5/16"

1.6

4.9

3.7

11.5

8.9

N/A


We would recommend the more flexible 5/16” air hose up to 25’ when the spray gun requirements are about 10 CFM, and the 3/8” hose for spray gun requirements over 10 CFM and up to 35’.

To set the desired gun incoming pressure without having to pre determine your actual pressure drop use this technique. Just pull back the gun trigger ¼” so as not to omit fluid, however air is exhausting. Than adjust the air regulator at the other end of the hose to the desired air pressure which we have labeled as dynamic air pressure.

Handle: news/adjusting-for-air-line-pressure-drop-at-the-gun