User manual BENDIX TW-12 CONTROL VALVE

[. . . ] Refer to the following chart and figure one. Connection Supply Delivery Vent Body Ident. xx OPERATION SYSTEM CONNECTIONS Although the TW-12TM valve can be used in a variety of different systems and connected in different ways, figure 2 illustrates a typical hydraulic parking brake system. In this system the TW-12TM valve controls an HR-1TM hydraulic relay that in turn applies and releases hydraulic spring brakes. VALVE OPERATION Parking Brakes Applied With hydraulic fluid flowing to the supply port (Figure 1) and the piston in the upward position, fluid flow into the TW-12TM control valve is stopped at the closed inlet valve. SD-03-3625 1 IN POWER STEERING GEAR OUT IN OUT HYDRAULIC BRAKE BOOSTER IN TW-12TM CONTROL VALVE MASTER CYLINDER RETURN TO SERVICE BRAKES DELIVERY SUPPLY SUPPLY CONTROL HYDRAULIC SPRING BRAKE ACTUATOR DELIVERY DELIVERY HYDRAULIC RESERVOIR RETURN RETURN HR-1TM HYDRAULIC RELAY HYDRAULIC SPRING BRAKE ACTUATOR IN RETURN POWER STEERING PUMP OUT FIGURE 2 - TW-12TM CONTROL VALVE HYDRAULIC PARK SYSTEM The TW-12TM valve delivery port is open to its return port through a passage in the center of the piston. Parking Brakes Released When the TW-12TM control valve plunger is depressed by the cam action of the lever (Figure 1) the piston contacts the inlet valve, closing the return passage. [. . . ] Bench testing of the TW-12TM valve is accomplished using air pressure regardless of its application or the braking media used in the vehicle brake system. OPERATING AND LEAKAGE TESTS Function test the TW-12TM valve while it is installed in the system by starting the engine and warming the vehicle brake system for 5 minutes. With 120psi applied to the supply and return ports simultaneously, apply a soap solution around the plunger and cam follower in the yoke assembly. Leakage should not exceed a 1" bubble in less than 5 seconds (100 SCCM). If the TW-12TM valve does not function as described or if excessive leakage is detected, it is recommended that it be replaced with a genuine Bendix® service replacement. 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 system components. At a minimum the TW-12TM valves should be inspected every 6 months or 1500 operating hours, whichever comes first. Inspect the exterior of the valve for signs of leakage and any apparent physical damage. Inspect the control cable and its connection point to the lever cam for damage and wear. If the TW-12TM control valve does not function as required or if leakage excessive, wear, or damage is noted during inspection, replace the valve with a genuine Bendix® service replacement unit. 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 the use of those tools. Following the vehicle manufacturer's recommended procedures, deactivate the electrical system in a manner that safely removes all electrical power from the vehicle. If the vehicle is equipped with an air over hydraulic brake system or any auxiliary pressurized air system, 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. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a component or pipe plug unless you are certain all system pressure has been depleted. Never attempt to disassemble a component until you have read and understand all recommended procedures. Some components contain powerful springs and injury can result if not properly disassembled. [. . . ] 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. VALVE REMOVAL 1. Park the vehicle on a level surface and block the wheels and/or hold the vehicle by means other than the service brakes. In the case of a hydraulic brake system consult the vehicle manual for proper procedures to be followed. Identify and mark or label all lines and their respective connections on the valve to facilitate ease of installation. 3 4. [. . . ]