User manual BENDIX TP-4 TRACTOR PROTECTION VALVE

[. . . ] DOUBLE CHECK VALVE PORTIONS There are two double check valves in the TP-4TM tractor protection valve, and they work in combination with each other to perform the following functions: 1. To permit the trailer hand control valve to be used for applying trailer service brakes only. To permit either the primary or secondary circuit from the dual brake valve to apply trailer brakes if air is lost in either one of the circuits. Each double check valve has two separate inlets and one common outlet, and the passage of air can be traced by referring to Schematic Figure 3. Double check valve A inlets are connected to the trailer hand control valve and the secondary delivery circuit of the dual brake valve. [. . . ] Leakage at port indicates double check valve requires servicing. Remove plug from line and reconnect to manifold. 3 SERVICE CHECKS OPERATING AND LEAKAGE CHECKS 1. With ignition switch on, place tractor protection control valve in emergency position. If vehicle is equipped with emergency stop light switch, trailer stop lights should function. Charge air brake system to governor cut-out and block wheels. Apply trailer hand control valve and check at open tractor service hose coupling for leakage. Excessive leakage would indicate faulty tractor protection valve inlet valve. (Item 6, Figure 2) TRAILER CONTROL VALVE TRAILER SUPPLY VALVE TWO WAY VALVE TO LIMITING AND Q. R. VALVE TO TRAILER EMERGENCY SECONDARY RESERVOIR DUAL BRAKE VALVE PRIMARY RESERVOIR A B C VENT TRAILER EMERGENCY STOP LIGHT SWITCH STOP LIGHT SWITCH TO TRAILER SERVICE FIGURE 5 TP-4TM TRACTOR PROTECTION VALVE (SERVICE APPLICATION) 10. Disconnect line from secondary circuit delivery (SCD) port and plug end of line. Make a foot brake valve application and check secondary circuit delivery (SCD) port of valve for leakage. Leakage at port indicates double check valve requires servicing. Remove plug from line and reconnect to valve. Make a foot valve application and test for gasket leakage. (See #4 "Assembly" for Proper Torque Sequence. ) If the TP-4TM tractor protection valve does not function as described above or leakage is excessive, it is recommended that it be replaced with a new or remanufactured unit, or repaired with genuine Bendix parts available at authorized Bendix parts outlets, in which case the following should prove helpful. 4. Remove large retaining ring (13) from lower body. Remove valve retainer (14), spring (7) and inlet valve (6). (NOTE: Older revision valves may have an o-ring (1), sealing disc (16) and small retaining ring (15) as shown in Figure 3. These need not be disturbed unless leakage was noted, in which case the retaining ring must be removed and the o-ring replaced. ) CLEANING AND INSPECTION 1. Clean all metal parts in mineral spirits and dry them completely. Inspect all parts for excessive wear or deterioration. Check the valve spring for cracks or corrosion. [. . . ] 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. 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. [. . . ]