Bendix® SR-5™ Trailer Spring Brake Valve
PRESSURE
PROTECTION
VALVE
™
VALVE
SR-5
IDENTIFICATION
HOLE
COVER*
1/4” NPT TRAILER
SUPPLY
1/4” NPT TRAILER
SERVICE
FIGURE 1 - BENDIX
®
SR-5™ TRAILER SPRING BRAKE VALVE (*SHOWN WITH OPTIONAL ANTI-COMPOUNDING COVER)
3/8” NPT
DELIVERY (4)
EXHAUST
SD-03-4516
1/4” NPT
SERVICE
RESERVOIR
(2)
1/2” OR 3/4” NPT
SPRING BRAKE
RESERVOIR
DESCRIPTION
The Bendix® SR-5™ valve is a reservoir-mounted trailer
valve that can control up to four spring brake actuators
during parking or emergency applications. It has the
following capabilities:
• Automatically applies trailer spring brakes in the event
of a breakaway or trailer supply line failure.
• Protects trailer reservoir(s) air pressure in the event of
a breakaway or trailer supply line failure.
• Allows no automatic trailer spring brake application
with air pressure loss in trailer reservoir(s).
• Allows the trailer spring brakes to be applied and released
repeatedly with a failed trailer reservoir(s):
• Optional anti-compounding-prevents an overriding
service brake signal while the trailer supply line is at
atmospheric pressure.
• Does not allow service system charging if a failure occurs
in the parking brake circuit.
PORTS
1 - 1/2" or 3/4" NPT Spring Brake Reservoir Mounting
(SPR BK RES)
1 - 1/4"-18 NPT Trailer Supply (TRL SUP)
1 - 1/4"-18 NPT Trailer Service (TRL SER)
4 - 3/8"-18 NPT Delivery (DEL)
2 - 1/4"-18 Service Reservoir (SERV RES)
1 - Exhaust (EXH)
The SR-5™ valve appears very similar to the Bendix® SR-2™
valve. Both valves consist of a die-cast aluminum body and
cover, pressure protection valve, and reservoir-mounting
nipple. However, Figure 1 notes the distinguishing
characteristic of the SR-5™ valve–a hole drilled into the
fl at surface between the pressure protection valve and
the body.
1
TRAILER SERVICE
SERVICE/SPRING BRAKE
RESERVOIR
TRAILER SUPPLY
SERVICE
RELAY
VALVE
TWO-TANK SYSTEM
SERVICE/
SPRING BRAKE
RESERVOIR
™
SR-5
VALVE
TRAILER SERVICE
™
SERVICE/SPRING BRAKE
RESERVOIR
SR-5
VALVE
SERVICE
RELAY
VALVE
TRAILER SUPPLY
ONE-TANK SYSTEM
FIGURE 2 - TYPICAL SYSTEM SCHEMATICS WITH BENDIX® SR-5™ TRAILER SPRING BRAKE VALVE
2
SERVICE
SPRING BRAKE
RELAY
VALVE
FIGURE 3 - CHARGING BELOW 70 PSI
TRAILER SERVICE RES.
CHECK
VALVE
B
SERVICE/
RESERVOIR
CONNECTION
CHECK
VALVE
D
DELIVERY
SPRING
BRAKE
CHAMBER
TRAILER SERVICE
PASSAGE A
TRAILER SUPPLY
CONTROL PISTON
EXHAUST
OPERATION
CHARGING BELOW 70 PSI (SEE FIGURE 3)
Air fl ows through the trailer supply line, enters the Bendix
SR-5™ valve trailer supply port, and moves the control
piston. The control piston contacts the control inlet/exhaust
valve, sealing off the piston’s exhaust passage.
As piston travel continues, the control inlet valve opens. Air
acting on the control piston also fl ows through passage A,
unseating check valve B, and fl owing past the open control
TRAILER SERVICE RES.
CHECK
VALVE B
SERVICE/
SPRING BRAKE
SERVICE
RELAY
VALVE
RESERVOIR
CONNECTION
®
inlet valve. This air fl ows into the spring brake cavities,
releasing the spring brakes.
CHARGING ABOVE 85 PSI (SEE FIGURE 4)
Air pressure acting on the control piston and fl owing
through passage A also acts on pressure protection valve
C. At approximately 85 psi, valve C opens. This allows
the air to fl ow past check valve D and charge the trailer
reservoir(s). The trailer braking system is now in the normal
run mode. Service braking occurs through the trailer
service relay valve.
TRAILER SERVICE
CHECK
VALVE D
PRESSURE
PROTECTION
VALVE C
PASSAGE A
FIGURE 4 - CHARGING ABOVE 85 PSI
DELIVERY
SPRING
BRAKE
CHAMBER
EXHAUST
CONTROL PISTON
3
TRAILER SERVICE RES.
CHECK
VALVE D
CHECK
VALVE B
SERVICE/
SERVICE
RELAY
VALVE
FIGURE 5 - P ARK APPLICA TION
SPRING BRAKE
RESERVOIR
CONNECTION
PARK APPLICATION (SEE FIGURE 5)
To park the trailer, either the trailer air supply valve or the
system park control valve (in the tractor) is actuated. This
vents the trailer supply line. The control piston, no longer
under supply pressure, is moved by air pressure on its
delivery side. This allows the control piston to move to the
exhaust position. The control inlet valve closes and the
exhaust valve opens, allowing air from the spring brakes
to exhaust through the passage in the control piston and
apply the brakes. Check valves B and D close, preventing
trailer reservoir air pressure loss through passage A.
TRAILER SERVICE
PRESSURE
PROTECTION
VALVE C
PASSAGE A
TRAILER SUPPLY
CONTROL PISTON
EXHAUST
SPRING
BRAKE
CHAMBER
PARK RELEASE WITH TRAILER CHARGED
(SEE FIGURE 6)
To release a park application with the trailer charged, the
trailer supply valve (in the cab) is actuated. Air fl ows through
the trailer supply line and enters the Bendix® SR-5™ valve
trailer supply port. With a minimum of 55 psi on the control
piston, the piston will move, sealing its exhaust passage.
As piston travel continues, the inlet valve opens. Reservoir
air (approx. 1 10 psi) then fl ows through check valve F , past
the open inlet, and out to the spring brake chambers to
release the brakes.
TRAILER SERVICE RES.
CHECK
SERVICE/
SPRING
SERVICE
RELAY
VALVE
FIGURE 6 - PARK RELEASE WITH TRAILER CHARGED
4
BRAKE
RESERVOIR
CONNECTION
VALVE F
SPRING
BRAKE
CHAMBER
TRAILER SERVICE
CHECK
VALVE D
CHECK
VALVE B
TRAILER SUPPLY
CONTROL PISTON
EXHAUST
PASSAGE
TRAILER SERVICE
CHECK
VALVE F
SERVICE/
SPRING BRAKE
SERVICE
RELAY
VALVE
FIGURE 7 - OPTIONAL ANTI-COMPOUNDING
RESERVOIR
CONNECTION
Note that pressure protection valve C will open if trailer
supply air is greater than 70 psi. But check valves B and
D will not open unless release pressure from the tractor
exceeds trailer reservoir pressure.
ANTI-COMPOUNDING (SEE FIGURE 7)
ANTI-COMPOUNDING
LINE
CHECK
VALVE E
TRAILER SUPPLY
EXHAUST
DELIVERY
SPRING BRAKE
CHAMBER
The Bendix® SR-5™ valve has an optional anti-compounding
feature. (See Figure 7.) A single check valve in the SR-5™
valve cover prevents brake compounding (simultaneous
spring brake and service brake application), which creates
extra load on foundation brake components.
If a trailer service application is being made and at the
same instant a park application is made, air in the service
line fl ows through single check valve E in the SR-5™ valve
cover. Pressure is maintained on the control piston, while
air also fl ows out the trailer supply line and exhausts
through the tractor protection control. Future compounding
is prevented by the closed tractor protection valve.
5
TRAILER SERVICE
TRAILER SERVICE RESERVOIR
CHECK
VALVE B
SERVICE/
SERVICE
RELAY
VALVE
FIGURE 8 - FAILED TRAILER RESERVOIR
SPRING BRAKE
RESERVOIR
CONNECTION
CHAMBER
FAILED TRAILER RESERVOIR (SEE FIGURE 8)
Should trailer reservoir pressure be lost, trailer service
braking is no longer available. Pressure protection valve
C will close at approximately 70 psi (minimum), retaining
air pressure in the trailer supply line.
The air held by the pressure protection valve will continue to
hold the control piston’s inlet valve open, supplying air to the
spring brakes. Thus, no automatic spring brake application
occurs. However, trailer supply line air can be used to apply
and release the trailer spring brakes repeatedly.
PRESSURE
PROTECTION
VALVE C
TRAILER SUPPLY
EXHAUST
SPRING
BRAKE
SERVICE CHECKS
1. Remove any accumulated contaminants. Visually
inspect the valve’s exterior for excessive corrosion
or physical damage. Repair/replace the valve as
necessary.
2. Inspect all air lines connected to the valve for signs of
wear or physical damage. Repair/replace as necessary .
3. Test air line fi ttings for excessive leakage and tighten
or replace as necessary.
OPERATIONAL AND LEAKAGE TESTS
PREVENTIVE MAINTENANCE
Important: Review the Bendix Warranty Policy before
performing any intrusive maintenance procedures. A
warranty may be voided if intrusive maintenance is
performed during the warranty period.
No two vehicles operate under identical conditions, as
a result, maintenance intervals may vary. Experience is
a valuable guide in determining the best maintenance
interval for air brake system components. At a minimum, the
Bendix® SR-5™ valve should be inspected every 6 months
or 1500 operating hours, whichever comes fi rst, for proper
operation. Should the SR-5™ valve not meet the elements
of the operational tests noted in this document, further
investigation and service of the valve may be required.
6
Check the tractor dash gauge against a gauge known to
be accurate before performing these tests. Connect the
tractor air lines to the trailer on which the SR-5™ valve is to
be tested. Block all wheels or hold the vehicles by means
other than air brakes.
1. Install a gauge in the trailer reservoir(s). Build tractor
and trailer to full system pressure by placing the
park control valve and the trailer air supply valve in
the charge position. As system pressure reaches
approximately 75-95 psi, the trailer spring brakes
should also build up to approximately 75- 95 psi before
the reservoir(s) begin to charge.
2. When full system pressure is reached, and the spring
brakes are fully released, apply a soap solution to the
SR-5™ valve exhaust port and the vent. A 1" bubble in
5 seconds is permissible.
3. Place the trailer air supply valve in the exhaust position.
The spring brakes should apply . Disconnect the trailer
supply line and apply a soap solution to check for leaks.
A 1" bubble in 5 seconds is permissible.
4. Reconnect the trailer supply hose coupling and
recharge the trailer system. The spring brakes should
release. Shut off the engine. Open the trailer reservoir
drain cock. The tractor air system should bleed down to
approximately 70 psi. The trailer spring brakes should
remain released. After the system is stabilized, leakage
at the open drain cock should not exceed a 1" bubble
in 5 seconds.
5. If the Bendix® SR-5™ valve does not function as
described; or if leakage is excessive, repair the valve,
or replace with a genuine Bendix service replacement
valve.
REMOVAL
1. Identify and mark or label all air lines and their
connections on the SR-5™ valve. Then disconnect the
air lines.
2. Remove the SR-5™ valve from the reservoir.
INSTALLATION
1. Install the SR-5™ valve on the reservoir.
2. Reconnect all air lines to the valve using the
identifi cation made in REMOVAL step 1.
3. Perform OPERA TIONAL AND LEAKAGE TESTS before
placing the vehicle back in service.
DISASSEMBLY
The following procedure is for reference only. Always
have the appropriate maintenance kit on hand, and use its
instructions in lieu of those presented here. Refer to Figure
9 throughout the procedure.
7
6
7
11
9
18
17
PIPE PLUG
12
10
4
5
VALVE BODY
25
24
8
23
2
1
FIGURE 9 - EXPLODED VIEW
16
15
18
17
3
14
PIPE PLUG
13
19
20
21
22
8
1. Remove the four screws (1) that secure the spring
retainer (2) to the valve body. Note that the retainer is
spring-loaded. Remove the screws while holding the
retainer against its spring load. Then slowly remove the
retainer.
2. Remove spring (3) and piston assembly (4).
3. Remove piston o-ring (5). Do not remove the retaining
ring and stem from the piston. The piston is serviced
as an assembly.
4. Note and mark the position of control piston cover (7).
Then remove the four screws (6) that secure the cover
to the body.
5. Remove cover (7) and sealing ring (8), control piston
(9), and spring (10).
6. Remove o-rings (11 & 12) from piston assembly.
7. Remove reservoir fi tting (13) and o-ring (14).
8. Remove spring (15) and inlet/exhaust valve (16).
9. Remove the pipe plugs that retain the three single check
valves. Two check valves are in the body, and one is
in the cover (7).
10. Remove check valve springs (17) and rubber check
valves (18).
11. With a pair of I.D. snap ring pliers, remove the snap
ring (19) in the end of the reservoir fi tting check valve
assembly. Remove spring seat (20), spring (21), and
check valve (22).
12. Remove screw (23), washer (24), and diaphragm (25)
from the exhaust port.
CLEANING AND INSPECTION
1. Inspect all parts for excessive wear or deterioration.
Inspect valve seats for nicks or burrs. Check the springs
for cracks or corrosion.
2. Inspect the bores of the valve housing for deep scuffi ng
or gouges.
Replace all non-metallic parts and any part not found to be
serviceable during inspection, using only genuine Bendix
replacement parts.
ASSEMBLY
Before assembling the Bendix
o-rings, o-ring grooves, piston bores, and metal-to-metal
moving surfaces with Bendix silicone lubricant BW-650-M
piece number 291126.
®
SR-5™ valve, lubricate all
1. Twist the springs (17) on each of the check valves (18).
Drop the assemblies into their respective bores in the
valve body and install the pipe plugs. Torque the plugs
to 140-170 inch pounds.
2. Place reservoir fi tting (13) upright, pipe threads down.
Drop check valve (22) into place. Install check valve
spring (21), spring seat (20), and snap ring (19). Install
o-ring (14) into fi tting.
3. Install inlet/exhaust valve (16) into valve body. NOTE:
The side with four protruding ears rests against the seat
in the body.
4. Place spring (15) in position on the inlet/exhaust valve.
Make sure the spring rests evenly on the four ears of
the inlet/exhaust valve and the rubber protrusion on
the valve fi ts into the spring’s inner diameter.
5. Properly align the inlet/exhaust valve springboard in
the recess at the end of the reservoir port fi tting (13).
Install the fi tting into the valve body . Torque to 200-300
inch pounds.
6. Install o-rings (1 1 & 12) into their respective grooves in
the control piston (9).
7. Drop and position the spring (10) into the valve body.
8. Make sure all parts are properly aligned, and install the
control piston (9) into the valve body.
9. Install sealing ring (8) in the cover (7), and install
cover onto valve body, using the identifi cation made
in DISASSEMBL Y step 4. Torque screws (6) to 40-60
inch pounds.
10. Install o-ring (5) in its groove in the pressure protection
piston (4). Install the piston assembly into the valve
body.
1 1. Position the spring (3) and spring retainer (2) on top of
the pressure protection piston assembly , and secure it
with the four screws (1). Torque to 20-30 inch pounds.
12. Install diaphragm (25), washer (24) and screw (23) into
the exhaust port. Torque screw to 15-25 inch pounds.
NOTE: BEFORE PLACING THE VEHICLE BACK INTO
SERVICE, PERFORM “OPERATIONAL AND
LEAKAGE TESTS,” LISTED IN THIS MANUAL.
NOTE: When using pipe thread sealant during assembly
and installation, take particular care to not allow
the sealant to get into the valve itself. Apply the
sealant beginning with the second thread back
from the end.
BW1680 © 2011 Bendix Commercial Vehicle Systems LLC. All rights reserved. 4/2011 Printed in U.S.A.
9
Loading...