Compressed Air Best Practices - October 2008 - (Page 59) Compressed Air Industry AUTOMOTIVE TRANSIT | 10/08 | Comparing Pressure Loss: Referring to the 80-psig inlet pressure curve, pressure loss versus flow FLOWS CFM GRINDER / SANDER HP CHIPPER / BREAKER WEIGHT PRESSURE LOSS 1⁄2" QD LOCK RING TYPE PRESSURE LOSS 1⁄2" QD EXHAUST TYPE PRESSURE LOSS 3⁄4" QD LOCK RING TYPE PRESSURE LOSS 3⁄4" QD EXHAUST TYPE 30 1 HP 30 lbs. 4.4 psid x2 8.8 psid 12 psid x2 24 psid 30(+) psid x2 60 psid 2.8 psid x2 5.6 psid 6.5 psid x2 13 psid 16 psid x2 32 psid 1.5 psid x2 3 psid 3.2 psid x2 6.4 psid 5.5 psid x2 11 psid .5 psid x2 1 psid 2 psid x2 4 psid 4 psid x2 8 psid 60 2 HP 60 lbs. 90 3 HP 90 lbs. Comments to the preceding chart (performance curves) p There is a significant difference in the pressure loss between the Ωî class quick disconnects. The exhaust coupler could work in an acceptable manner from less than 30 cfm to as much as 60 cfm (for example, on a whip hose) and still maintain 100 psig inlet above 80 psig to the tool or 90 psig inlet air 70 psig to the tool. The current lock ring/ball check nipple 1⁄2" quick disconnect appears acceptable at 30 cfm but at 60 cfm will probably not be acceptable. The 3⁄4" quick disconnects are closer in performance but the lock ring/ball check type has 30–40% more pressure loss. The 3⁄8" lock ring/ball check nipple quick disconnect supplied for test did not have the ball check valve in the nipple which accounts for its lower pressure drop compared to the 1⁄2" lock ring coupler which did. This of course means that the safety feature to control potential “hose whip” is not incorporated into the 3⁄8" lock ring set. We do not consider the 3 ⁄8" hose or quick disconnect a viable option in this application. p p Summary Air hoses and quick disconnects both have the same best practice guidelines — do not select or apply them without all the data. Too often, because they are a low initial cost system component, they are purchased and applied without a great deal of thought and effort. Misapplied they will “steal” great amounts of profit! For more information, contact Hank Van Ormer, tel: 740-862-4112, email: hankvanormer@aol.com, www.airpowerusainc.com www.airbestpractices.com 59 http://www.airpowerusainc.com http://www.airbestpractices.com
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