User manual BENDIX BP-1 BRAKE PROPORTIONING VALVES

[. . . ] When the trailer is disconnected from the tractor and the trailer supply valve is pulled out, the front axle of the tractor will receive 100% of the service brake application pressure and the rear axle or axles approximately 25%. As application pressure increases, the differences between the front axle and the rear axle(s) pressures diminish. 1 SD-03-952 A tractor that is equipped with both a front and rear axle brake proportioning valve with the trailer supply valve activated (tractor/trailer mode) will experience 50% of service brake application pressure on the front axle up to 40 psi. With service applications above 40 psi the differential between the supply and delivery diminishes until at 60 psi it is a one-to-one ratio. With the trailer supply valve pulled out, (bobtail mode) the front axle of the tractor will receive 100% of service brake application and the rear axle(s) approximately 25% during normal brake applications. [. . . ] 1 O-Ring 2 5 Inlet/Exhaust Valve 1 2 O-Ring 1 6 Spring 1 3 O-Ring 1 7 Sealing Ring 1 4 O-Ring 1 8 Spring 1 FIGURE 4 BP-1TM REAR BRAKE PROPORTIONING VALVE CUTAWAY VIEW 2. 78 COVER 3/8 P. T. 4 Spring 1 1 O-Ring 1 5 Inlet/Exhaust Valve 1 2 O-Ring 1 6 Spring 1 3 O-Ring 1 7 Sealing Ring 1 FIGURE 5 BP-1TM FRONT BRAKE PROPORTIONING VALVE CUTAWAY VIEW 1 LOWER PISTON BODY 7 4 2 4. 34 delivers 50% of the service application to the actuators. Service pressures above 40 psi begin to displace the upper piston and the differential between the supply and delivery diminishes until at 60 psi the spring force under the upper piston is totally overcome and the valve delivers a one-to-one ratio. See Figure 3, limiting mode. 3 KEY C-CONTROL D-DELIVERY S-SUPPLY TRACTOR PROTECTION CONTROL VALVE TRACTOR PROTECTION VALVE Key No. 1 1 1 Description BP-1TM (Rear) Valve TR-3TM Inversion Valve BP-1TM (Front) Valve REPLACES FRONT AXLE LIMITING VALVE TEE FITTING EXISTING LINE Ë Ê TEE FITTING Ì BRAKE VALVE EXISTING REAR AXLE SERVICE DELIVERY LINE REAR AXLE SERVICE RELAY VALVE EXISTING FRONT AXLE SERVICE DELIVERY LINE TEE FITTING REAR AXLE SERVICE RESERVOIR FIGURE 6 TYPICAL INSTALLATION SCHEMATIC OF BRAKE PROPORTIONING SYSTEM 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. Prior to returning the vehicle to service, make certain all components and systems are restored to their proper operating condition. 4. Install the BP-1TM rear valve into the service line from the brake valve. Connect the delivery line from the brake valve to the supply port of the BP-1TM valve and the delivery port of the BP-1TM valve to the control port on the relay valve. Tee the control port to the delivery of the trailer supply valve, the supply port to the supply line of the brake valve, and connect the delivery port to the control port of the BP-1TM valve. Note: If vehicle does not have a front axle ratio or limiting valve, proceed to "Operational Checks". If vehicle has a front axle ratio or limiting valve, continue with Step 6. Remove the existing front axle ratio or limiting valve and replace it with the BP-1TM front valve. Connect the front axle brake valve delivery line to the supply port of the BP-1TM valve, the delivery port of the BP-1TM valve to the front axle actuators, and the control port of the BP-1TM valve to the delivery of the TR-3TM inversion valve. INSTALLATION (REFER TO FIGURE 6) 1. The vehicle being fitted with a BP-1 TM rear brake proportioning valve must be equipped with a rear axle service relay valve. It cannot be installed on a vehicle utilizing a quick release valve system without a relay valve. For vehicles equipped with a front axle service ratio or limiting valve (such as the Bendix® LQ-4TM valve) it must be removed and replaced by the BP-1TM front valve provided in kit #209924. They are identified with a metal tag stamped `BP-1 Front' or `BP-1 Rear' attached to one of the cap screws on the cover. Mount the BP-1TM rear valve and the TR-3TM inversion valve in a protected area that is convenient to the service line between the brake valve and the relay valve. OPERATIONAL CHECKS After components have been installed and all connections made, perform the following checks. With the trailer supply valve pulled out (bobtail running position) install two air gauges in the service system; one at an actuator on the front axle and one at an actuator on a rear axle. 4 2. Make a service brake application with the foot valve and have another person or persons observe the gauges. [. . . ] Clean the exterior of the valve taking care to prevent contaminates from entering the open ports of the valve. DISASSEMBLY OF BP-1TM FRONT VALVE (REFER TO FIGURE 5) 1. Caution: Hold cover down against spring load and release gently when screws are removed. Retain the screws and the metal tag with `BP-1 Front' stamped on it. Remove the upper piston from the cover and the piston spring(4) and lower piston from the body. [. . . ]