Bendix Commercial Vehicle Systems QRN-2 QUICK RELEASE VALVE 3/04 - Manual (Page 2)

2
OPERATION
0 psi Crack & Differential Pressure
Unlike standard quick release valves, the QR-L ™ valve
maintains the same pressure at the supply and delivery
ports (0 psi crack and differential) throughout the entire
pressure range during both apply and release modes. Three
radial channels in the cap, along with a specially shaped
diaphragm, provide the QR-L
™ valve with this feature.
Apply
When air pressure enters the supply port, it causes the
center portion of the diaphragm to seal the exhaust in the
body. Supply air pressure simultaneously forces the edges
of the diaphragm away from its seat on the cap, allowing air
to flow freely out the delivery port. Delivery pressure is the
same as supply pressure.
Balance
When delivery air pressure (pressure beneath diaphragm)
is equal to supply air pressure above the diaphragm, the
outer edges of the diaphragm seat against the cap. The
exhaust remains sealed because air pressure bears against
the center portion of the diaphragm from one side only.
Release
When air pressure is removed or reduced rapidly at the
QR-L
™ valve supply port, the air pressure on the delivery
side of the diaphragm holds the outer edge of the diaphragm
against its seat on the cap while simultaneously moving
the center portion away from the exhaust port in the body.
Air from the delivery port flows out the exhaust ports. If air
pressure is reduced slowly at supply port, air may not flow
out the exhaust ports.
When delivery air pressure is fully exhausted, the diaphragm
will return to its natural state, with its outer edges seated
on the cap and the center portion seated against the exhaust
in the body.
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO
AVOID
PERSONAL INJURY OR DEATH:
When working on or around a vehicle, the following
general precautions should be observed at all times.
1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.
FIGURE 3 TYPICAL QR-L ™ INLINE QUICK RELEASE VALVE
AIR SYSTEM APPLICATION
FIGURE 5 QR-L ™ INLINE QUICK RELEASE VALVE BALANCED
MODE
Diaphragm
Supply
Delivery
Exhaust
Exhaust
Diaphragm
Supply
Delivery
Exhaust
Exhaust
FIGURE 6 QR-L ™ INLINE QUICK RELEASE VALVE RELEASE
MODE
Diaphragm
Supply
Delivery
FIGURE 4 QR-L ™ INLINE QUICK RELEASE VALVE AIR APPLIED
TO SUPPLY PORT
Exhaust
Exhaust
Trailer
Supply Valve
Trailer
Control
Valve
Tractor
Protection
Valve
Service
Brake
Valve
Control
Line QR-L ™
Valve
Supply Line
QR-L ™
Valve