BENDIX TCH-003-043 User's Manual
Contents
1. that require a certain flow rate to provide quick exhausting of air pressure Because of the nature of its operation line sizes and delivery volume are critical to rapid exhausting of the delivery pressure Bendix recommends 3 8 tubing outside diameter minimum for Supply Balance and Delivery lines for these Quick Release Valves If smaller line sizes are to be used or if the venting of supply pressure is restricted by other components BCVS recommends that the zero hysteresis type quick release valves not be used to ensure proper quick release function Bendix has released the following quick release valve part numbers with a 1 PSI maximum differential for use with smaller line sizes and unique application These are not zero hysteresis quick release valves Port Size NPT Part Number Model Supply Delivery Balance Exhaust 5009069 QR 1C 3 8 3 8 4 5008064 QR 1C 4 3 8 1 4 5009070 QR 1C YA 4 4 5009071 QR 1 3 8 4 5009009 QR 1 3 8 3 8 3 8 5009073 QRN 2 3 8 3 8 gt 72. Technical Bulletin Bulletin No TCH 003 043 A Effective Date 11 28 00 Cancels NA Page 1 of 1 subject ZERO HYSTERESIS QUICK RELEASE VALVE Bendix Commercial Vehicle Systems changed all QR 1 QR N2 and QR 1C quick release valves having a maximum differential of 1 PSI TMC I D QRV 010 to be zero hysteresis TMC I D QRV 000 All valves having a differential greater than the 1 PSI maximum were not impacted by this change This change was implemented on 10 15 97 as a product improvement for both service and park brake systems Bendix and other industry groups recommend that the pressure at all axles of a combination be within 2 PSI for control line pressures of 10 40 PSI Ref BW 1555 This pressure balance promotes brake balance provided other factors such a brake type friction formulation tires etc are sized properly per the gross axle weight regulations GAWR SAE J1859 defines hysteresis as the difference in the increasing and decreasing input pressure for a given output delivery pressure Conventional quick release valves with hysteresis can have a differential difference between inlet and outlet pressure as high as 20 PSI on release The zero hysteresis enables the output pressure to be equal for both increasing and decreasing pressures This improves the pneumatic brake balance on release and enables the recommendations for pneumatic brake balance to be met The quick release valves manufactured by Bendix are flow sensitive devices
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