BENDIX SD-03-4508 User Manual
®
Bendix® SR-1™ Spring Brake Valve
1/4 P.T.
DELIVERY
SD-03-4508
PISTON SPRING
(14)
PISTON (15)
1/4 P.T.
CONTROL
1/4 P.T.
RES. #1
FIGURE 1 - BENDIX
1/4 P.T.
SUPPLY
®
SR-1™ VALVE EXTERIOR AND SECTIONAL VIEW
PISTON O-RINGS
(16)
VALVE (12)
VALVE SPRING (11)
VALVE STOP (10)
O-RING (9)
CAP NUT (8)
DESCRIPTION:
The Bendix® SR-1™ spring brake valve is used in dual
or “split” air brake systems equipped with spring brake
actuators. The function of the SR-1 valve is to supply a
specifi c, limited hold-off pressure to the spring brakes, and
in the event of the loss of No. 1 service air pressure, to
modulate the spring brakes through the use of the service
brake valve.
The valve has four identifi ed 1/4" N.P.T.F. ports and a
diaphragm protected exhaust port. Two 5/16" diameter
holes are provided in the integral mounting bracket of the
valve body. The SR-1 valve must be mounted with the
exhaust port down toward the road surface.
COVER (13)
INLET &
EXHAUST
VALVE (7)
PISTON SPRINGS
DIAPHRAGM
(6)
(14)
O-RING
(LARGE)
(18)
PISTON (17)
O-RING
(SMALL) (19)
BODY
CHECK
VALVE (4)
CHECK
VALVE SPRING (2)
PIPE PLUG
(1)
EXHAUST
COVER (5)
OPERATION - INITIAL AIR SYSTEM CHARGE
Air fl owing from the No. 1 reservoir only enters the reservoir
port of the SR-1 valve. This air remains under piston A as
system pressure builds. With No. 1 reservoir pressure
below approximately 55 P.S.I. the spring above piston A
forces it into contact with inlet and exhaust valve A causing
the exhaust to seal and the inlet to open. Refer to Figure 3.
With air system pressure above approximately 55 P.S.I. in
No. 1 & 2 service reservoirs, piston A has moved against
the force of the spring above it, allowing the inlet of valve A
to close and opening the hollow exhaust passage through
piston A. Refer to Figure 4.
1
BRAKE
CHAMBER
BRAKE
VALVE
PARK
CONTROL
VALVE
SLACK
ADJUSTER
SPRING
BRAKE
QUICK
RELEASE
VALVE
MODULATOR
FIGURE 2 - SYSTEM SCHEMATIC
PARK
CONTROL
VALVE
#2 SERVICE
RESERVOIR
DOUBLE
CHECK
VALVE
SUPPLY
DOUBLE
CHECK VALVE
#2 SERVICE
RESERVOIR
#1 SERVICE
RESERVOIR
PISTON A
INLET &
EXHAUST A
#1 SERVICE
RESERVOIR
™
R-8
VALVE
INLET
&
EXHAUST
B
EXHAUST
®
R-14
RELAY
VALVE
PISTON B
CHECK VALVE
®
R-14
RELAY
VALVE
BRAKE
VALVE
FIGURE 3 - RESERVOIRS CHARGING - BELOW 55 P.S.I.
2
SPRING
BRAKE
PARK
CONTROL
VALVE
PISTON A
INLET &
EXHAUST A
PISTON B
CHECK VALVE
R-14
RELAY
VALVE
®
#2 SERVICE
RESERVOIR
DOUBLE
CHECK
VALVE
FIGURE 4 - RESERVOIRS CHARGING - ABOVE 55 P.S.I.
PARK
CONTROL
VALVE
#2 SERVICE
RESERVOIR
DOUBLE
CHECK
VALVE
#1 SERVICE
RESERVOIR
EXHAUST A
#1 SERVICE
RESERVOIR
PISTON A
INLET &
INLET
&
EXHAUST
B
INLET
&
EXHAUST
B
EXHAUST
EXHAUST
PISTON B
CHECK VALVE
R-14
RELAY
VALVE
SPRING
BRAKE
®
BRAKE
VALVE
FIGURE 5 - PARKING BRAKE SUPPLY DELIVERY LESS THAN 95 P.S.I.
OPERATION - CHARGING SPRING BRAKE
ACTUATORS LESS THAN 95 PSI
With the air brake system charged and the dash valve
pushed in, air enters the Bendix
Air entering the supply port fl ows past inlet and exhaust
valve B to the underside of piston B and out the delivery
port of the SR-1 valve to the Bendix® R-14® parking relay
valve then to the emergency air connection at the spring
brake actuator. Note that the springs above piston B force
it into contact with inlet and exhaust valve B. In the position
®
SR-1™ valve supply port.
OPERATION - CHARGING SPRING BRAKE
ACTUATORS ABOVE 95 PSI
When air pressure beneath piston B is approximately
95* P.S.I., piston B rises slightly, against the force of the
springs above it, allowing the inlet of valve B to close. The
exhaust through valve B remains closed. The closing of
the inlet portion of valve B retains approximately 95* P.S.I.
in the hold- off cavity of the spring brake actuators while
allowing full air system pressure to build elsewhere. Refer
to Figures 5 and 6.
shown the exhaust is closed and the inlet is open.
SPRING
BRAKE
3
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