SEAL-SPOOL 1175241 - Caterpillar

Illustration 1 g00455022
Components for air system and brakes (A) Scraper (B) Tractor (C) Operator compartment (1) Tractor brake actuator (2) Scraper brake actuator (3) Governor control valve (4) Throttle lock solenoid (standard on 627F, attachment on 621F and 623F ) (5) Scraper governor control valve (only on 627F ) (6) Rear engine throttle lock solenoid (only on 627F ) (7) Service brake control valve (8) Pressure switch (throttle lock enable switch) (9) Retarder air control valve (10) Air relief valve (11) Check valve (12) Tractor air reservoir (13) Drain valve (14) Check valve (15) Quick release and holding valve (16) Check valve (17) Drain valve (18) Scraper air reservoir (19) Scraper relay valve (20) Differential lock (21) Quick release and holding valve (22) Pressure switch (23) Quick release valve (24) Differential lock solenoid valve (25) Double check valve (26) Pressure protection valve (27) Air horn solenoid valve (28) Air horn (29) Parking and secondary brake control valve (30) Pressure switch (31) Governor control cylinder (32) Retarder valve (only on 627F ) (33) Pressure regulator (only on 627F ) (34) Tractor relay valve (35) Governor control cylinder (only on 627F ) (36) Pressure regulator (37) Retarder valve (38) Air compressor governor (39) Air compressor (40) Air dryerAll of the brakes in the brake system are shoe type brakes. There is a brake at each wheel of the tractor and the scraper. These brakes are activated by air pressure in brake actuators (1) and (2) . The brake actuators provide three types of brakes:
service
secondary
parkingAir compressor (39) sends air to tractor air reservoirs (12) and scraper air reservoir (18) . The flow of air is divided into three separate circuits:
service brake
parking and secondary brake
accessory air circuitsService brake circuit
When the brake pedal is pushed, pressurized air is sent from brake control valve (7) to tractor relay valve (34) . The air then flows from the relay valve to the service brake air chambers of tractor brake actuators (1) . Air pressure goes to tractor relay valve (34) and to scraper relay valve (19) . This air pressure opens scraper relay valve (19) which permits air pressure to go from scraper air reservoir (18) to scraper service brake actuators (2) .When the service brakes are applied, air pressure from parking and secondary brake control valve (29) flows through the following components: double check valve (25), quick release and holding valves (15) and (21) and parking and secondary brake chambers of brake actuators (1) and (2) . This releases the parking and secondary brakes. When the brake pedal is pushed before the parking and secondary brakes are released, double check valve (25) allows air pressure to go to quick release and holding valves (15) and (21) and to the parking and secondary brake chambers of brake actuators (1) and (2) . This prevents the application of the parking and secondary brake in addition to the service brake which prevents damage to