SD-03-4504 ® Bendix® R-7™ Modulating Valve EXHAUST CONTROL PORT EXHAUST INLET VALVE SPRING SUPPLY PORT MOUNTING HOLE (2) CONTROL PORT CONTROL PISTON DOUBLE CHECK VALVE (SUPPLY PORT & BALANCE PORT) INLET EXHAUST VALVE DELIVERY (2) MOUNTING SURFACE BALANCE PORT INLET VALVE SEAT MOUNTING HOLE (2) SINGLE CHECK VALVE BALANCE PISTON DELIVERY PORT (2) INNER SPRING SUPPLY OUTER SPRING ADJUSTING SCREW BALANCE CONTROL EXHAUST FIGURE 1 - EXTERIOR & INVERTED VIEW FIGURE 2 - SECTIONAL VIEW DESCRIPTION Note for model year 2001 and later International Trucks only: There is an inverted R-7™ valve, which appears inverted from the other pictures in this document. A standard R-7™ valve and an inverted R-7™ valve are not interchangeable. See Figure 1 for a picture of an inverted R-7™ valve. The R-7™ modulating valve is used in conjunction with a dual air brake system and spring brake actuators, and performs four functions: 1. Limits hold-off pressure to the spring brake actuators (adjustable). 2. Provides for quick release of air pressure from the spring cavity of the spring brake actuator allowing a fast application of the spring brake actuators. 3. Modulates spring brake actuator application should a failure occur in the service brake system. 4. Prevents compounding of service and spring forces. The valve has one 1/4" control, one 3/8" supply, one 1/4" balance, two 3/8" delivery NPTF ports, and an exhaust port protected by an exhaust diaphragm. The valve incorporates two 13/32" holes for mounting. OPERATION - CHARGING SPRING BRAKE ACTUATORS (FIGURE 3) Air pressure used to control the spring brake actuators enters the valve through the supply port, passing through one side of the double check valve, through the open inlet valve, over the balance piston, and out the delivery ports to the spring brake actuators. When air pressure in the spring brake actuator cavity has released the spring brake actuators and when air pressure on top of the balance piston is sufficient to overcome the force of the balance piston spring, the balance piston moves allowing the inlet valve spring to close the inlet valve, shutting off further air pressure from the reservoir supplying the modulating valve. 1 #1 RES. SECONDARY SERVICE CIRCUIT CONTROL PORT EXHAUST PORT #2 RES. #1 RES. SECONDARY SERVICE CIRCUIT DUAL BRAKE VALVE CONTROL PISTON EXHAUST CONTROL PORT PORT PRIMARY SERVICE CIRCUIT BALANCE PORT #2 RES. CONTROL PISTON DUAL BRAKE VALVE PRIMARY SERVICE CIRCUIT BALANCE PORT DOUBLE CHECK VALVE SPRING BRAKE ACTUATOR DOUBLE CHECK VALVE SUPPLY PORT INLET/EXHAUST VALVE SINGLE CHECK VALVE PRIMARY SECONDARY PARK - PARK CONTROL VALVE SUPPLY PORT SPRING BRAKE ACTUATOR + SPRING BRAKE HOLD-OFF PRESSURE - SERVICE AIR PRESSURE o ATMOSPHERE PRESSURE PARK CONTROL VALVE SINGLE CHECK VALVE INLET/EXHAUST VALVE BALANCE PISTON BALANCE PISTON PRIMARY SECONDARY PARK - + SPRING BRAKE HOLD-OFF PRESSURE - SERVICE AIR PRESSURE o ATMOSPHERE PRESSURE FIGURE 5 - SERVICE APPLICATION LOSS OF PRIMARY CIRCUIT FIGURE 3 - CHARGING OPERATION - SERVICE APPLICATION WITH LOSS OF AIR IN PRIMARY CIRCUIT (FIGURE 5) #1 RES. SECONDARY SERVICE CIRCUIT CONTROL PORT EXHAUST PORT CONTROL PISTON #2 RES. DUAL BRAKE VALVE PRIMARY SERVICE CIRCUIT BALANCE PORT DOUBLE CHECK VALVE SUPPLY PORT SPRING BRAKE ACTUATOR PRIMARY SECONDARY PARK - INLET/EXHAUST VALVE SINGLE CHECK VALVE PARK CONTROL VALVE BALANCE PISTON A service application made with a loss of air in the primary circuit would result in reduced air pressure delivered to the lower area of the control piston. Air pressure from the secondary circuit on top of the control piston would force the piston down, opening the exhaust valve and allowing air pressure in the spring cavity of the spring brake actuator to release and the spring brake actuator to apply the brakes. The pressure differential between the primary and secondary circuits regulates the amount of air pressure released from the spring cavity of the spring brake actuator. This results in a total brake application on the rear axle which is proportionate to the braking on the other axles. + SPRING BRAKE HOLD-OFF PRESSURE - SERVICE AIR PRESSURE o ATMOSPHERE PRESSURE FIGURE 4 - NORMAL SERVICE APPLICATION #1 RES. SECONDARY SERVICE CIRCUIT NOTE: The force of the spring below the balance piston is adjustable by an external screw on the modulating valve. This adjustment is normally made so that the inlet valve will close at a slightly greater pressure than the hold-off pressure of the spring brake actuator, but below maximum system pressure. OPERATION - NORMAL SERVICE APPLICATION (FIGURE 4) When a service application is made by actuating the dual brake valve, air from the primary circuit is delivered to the lower side of the control piston through the balance port, and air from the secondary circuit is delivered to the top of the control piston through the control port. Because air pressure from the primary and secondary circuits are not equal, there will be a slight movement of the control piston. 2 EXHAUST CONTROL PORT PORT #2 RES. CONTROL PISTON DUAL BRAKE VALVE PRIMARY SERVICE CIRCUIT BALANCE PORT DOUBLE CHECK VALVE SUPPLY PORT SPRING BRAKE ACTUATOR PRIMARY SECONDARY PARK - INLET/EXHAUST VALVE SINGLE CHECK VALVE PARK CONTROL VALVE BALANCE PISTON + SPRING BRAKE HOLD-OFF PRESSURE - SERVICE AIR PRESSURE o ATMOSPHERE PRESSURE FIGURE 6 - SERVICE APPLICATION LOSS OF SECONDARY CIRCUIT OPERATION - SERVICE APPLICATION WITH LOSS OF AIR IN SECONDARY CIRCUIT (FIGURE 6) A service application made with a loss of air in the secondary circuit would result in less or no air delivered to the top of the control piston; however, the piston would not move and braking on the rear axle(s) is assured because the primary circuit supplies rear axle service brakes. The spring brake actuators will not be actuated. OPERATION - PARKING (FIGURE 7) When the handle of the parking control valve is placed in the “park” (exhaust) position, the modulating valve’s supply air pressure and the air pressure in the spring brake actuator cavities is exhausted. The single check valve speeds the exhaust of air from the actuator cavities by allowing the air on top of the balance piston to exhaust by the double check valve through the supply port to atmosphere. When air pressure drops sufficiently, the balance piston opens the inlet valve thus opening the larger passage in the modulating valve insuring rapid exhaust of the balance of air pressure in the spring cavity of the spring brake actuator. #1 RES. SECONDARY SERVICE CIRCUIT EXHAUST CONTROL PORT PORT CONTROL PISTON #2 RES. DUAL BRAKE VALVE PRIMARY SERVICE CIRCUIT BALANCE PORT DOUBLE CHECK VALVE SUPPLY PORT SPRING BRAKE ACTUATOR SINGLE CHECK VALVE INLET/EXHAUST VALVE PRIMARY SECONDARY PARK - PARK CONTROL VALVE BALANCE PISTON + SPRING BRAKE HOLD-OFF PRESSURE - SERVICE AIR PRESSURE o ATMOSPHERE PRESSURE FIGURE 7 - PARKING 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 R-7™ valve should be inspected every 6 months or 1500 operating hours, whichever comes first, for proper operation. Should the R-7™ valve not meet the elements of the operational tests noted in this document, further investigation and service of the valve may be required. SERVICE TESTS 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. 2. Stop the engine and remove ignition key when working under or around the vehicle. When working in the engine compartment, the engine should be shut off and the ignition key should be removed. Where circumstances require that the engine be in operation, EXTREME CAUTION should be used to prevent personal injury resulting from contact with moving, rotating, leaking, heated or electrically charged components. 3. Do not attempt to install, remove, disassemble or assemble a component until you have read and thoroughly understand the recommended procedures. Use only the proper tools and observe all precautions pertaining to use of those tools. 4. If the work is being performed on the vehicle’s air brake system, or any auxiliary pressurized air systems, make certain to drain the air pressure from all reservoirs before beginning ANY work on the vehicle. If the vehicle is equipped with an AD-IS™ air dryer system or a dryer reservoir module, be sure to drain the purge reservoir. 5. Following the vehicle manufacturer’s recommended procedures, deactivate the electrical system in a manner that safely removes all electrical power from the vehicle. 6. Never exceed manufacturer’s recommended pressures. 7. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a component or plug unless you are certain all system pressure has been depleted. 8. Use only genuine Bendix® replacement parts, components and kits. Replacement hardware, tubing, hose, fittings, etc. must be of equivalent size, type and strength as original equipment and be designed specifically for such applications and systems. 9. Components with stripped threads or damaged parts should be replaced rather than repaired. Do not attempt repairs requiring machining or welding unless specifically stated and approved by the vehicle and component manufacturer. 10. Prior to returning the vehicle to service, make certain all components and systems are restored to their proper operating condition. 3 OPERATING TEST Block vehicle and hold by means other than vehicle brakes. Charge air brake system to governor cut-out pressure. 1. Place parking control valve in “park” position. Observe that spring brake actuators apply promptly. Remove one line from delivery port of valve and install test gauge known to be accurate. Place parking control valve in “release” position. Observe that spring brake actuators release fully. 2. With parking control valve in “release” position, note gauge pressure reading. (Check vehicle manual for correct spring brake actuator hold-off pressure.) If pressure reading is incorrect, modulating valve should be adjusted. (See section “Adjustment of Modulating Valve - Spring Brake Actuator Hold-Off Pressure”.) 3. Place parking control valve in “park” position - gauge reading should drop to zero promptly. A lag (more than 1 second) in drop of pressure would indicate faulty operation of the single check valve (within the modulating valve). 4. With the parking control valve in the “park” position fully apply foot brake valve several times and note a pressure reading increase on the gauge each time the brake is applied. If pressure reading does not occur, the modulating valve requires servicing or replacing. 5. Place parking control valve in “release” position. Determine the reservoir which supplies balance port and drain completely. Apply foot brake valve several times and note that pressure reading on gauge decreases each time foot brake valve is applied. After foot brake valve has been applied several times, pressure on gauge will drop to the point where release of the spring brake actuators will no longer occur. LEAKAGE TEST Place the park control valve in the “release” position; using a soap solution, coat exhaust and vent hole (in proximity of adjusting screw). Slight bubble leakage permitted. If the valve does not function as described, or if leakage is excessive, it is recommended that it be repaired or replaced with a genuine Bendix service replacement valve. ADJUSTMENT OF MODULATING VALVE - SPRING BRAKE ACTUATOR HOLD-OFF PRESSURE Block vehicle by means other than vehicle brakes. If it has been ascertained that hold-off pressure for the spring brake actuators is incorrect (see section “Operating Test”), adjustment should be made as follows: 4 1. Build system pressure to governor cut-out (approximately 120 psi). It is important that system leakage for a single vehicle not exceed a 2 psi drop in one (1) minute with brakes released. Correct system leakage before proceeding with adjustment. 2. Place parking control valve in “park” position and install an accurate test gauge in a delivery port of the modulating valve. Place parking control valve in “release” position and observe pressure reading on the test gauge. Refer to vehicle manual for recommended pressure. Adjust as necessary. TO RAISE HOLD-OFF PRESSURE Loosen lock nut. Turn adjusting screw clockwise and observe reading on gauge. To raise hold-off pressure, turn adjusting screw clockwise - to lower hold-off pressure, turn adjusting screw counterclockwise until pressure is below that desired and then turn screw clockwise to desired pressure. Tighten locknut securely after completing adjustment. DISASSEMBLY 1. Remove exhaust cover screw, exhaust cover and exhaust diaphragm. 2. Remove four (4) cap screws and lockwashers and cover. Remove o-ring from cover. 3. Remove control piston and remove three (3) o-rings from control piston. 4. Remove large retaining ring from body and remove inlet/ exhaust valve assembly. 5. Remove ring from inlet/exhaust valve assembly. Remove o-ring retainer, remove o-ring from o-ring retainer. Remove washer and spring. Remove valve retainer and valve from valve body. 6. Remove four (4) cap screws from other cover. (Do not disturb center cap screw unless spring brake hold off pressure is to be adjusted). See Section “Adjustment of Modulating Valve”. 7. Remove cover and inner and outer springs. 8. Remove balance piston. Remove o-ring from balance piston. 9. Remove retaining ring from supply port and remove supply adapter and double check valve assembly. Remove o-ring from supply adapter. Remove double check valve from shuttle guide. (NOTE: To ease removal of supply adapter, a pipe nipple can be screwed in adapter.) 10. Remove allen head plug from single check valve service port. Remove single check valve assembly. (If single check valve is difficult to remove, it can be dislodged inside bore of body of valve). ASSEMBLY Before assembly, lightly lubricate all o-rings, bores and mating surfaces with silicone lubricant BW-650-M (Bendix Pc. No. 291126). 1. Install single check valve assembly and allen head plug. Tighten securely. 2. Install o-ring on supply adapter, install shuttle guide over supply adapter and install double check valve in guide. 3. Install adapter and double check valve assembly in supply port. Install retaining ring, making certain the retaining ring is engaged in groove. 4. Install o-ring on balance piston and install balance piston in bore of body. 5. Install inner and outer springs and spring seat (note that cone shaped protrusion on spring seat faces springs). 6. Install cover with four (4) cap screws, torque to approximately 45 in. lbs. (Do not disturb center cap screw unless spring brake hold-off pressure is to be adjusted. See section “Adjustment of Modulating Valve”). 7. Install valve on valve body. Install valve retainer, spring, and washer. Install o-ring on o-ring retainer. Install o-ring retainer, compress retainer and install retaining ring, making certain retaining ring is engaged in groove of valve body. 8. Install inlet/exhaust valve assembly in body. Install retaining ring making certain the retaining ring is engaged in groove in bore of body. 9. Install three (3) o-rings on control piston. Install control piston in body. (Larger diameter stem should point up). 10. Install o-ring on cover. Install cover with four (4) cap screws and lockwashers. Torque to approximately 100 in. lbs. 11. Install exhaust diaphragm and exhaust cover. TESTING REBUILT R-7™ MODULATING VALVE Perform operating and leakage tests as outlined in “Service Tests” section. 5 6 BW1445 © 2004 Bendix Commercial Vehicle Systems LLC. All rights reserved. 3/2004 Printed in U.S.A.