OPERATOR AR 2195157 - Caterpillar

Illustration 1 g01031740The brake release sequence valve is located on the left side of the rear frame.The sequence valve is a pilot operated, normally closed cartridge type valve.
Illustration 2 g01031738
(1) Port
(2) Port
(3) Port
(4) Brake release sequence valve Recovery Bar
The sequence valve ensures that the brake release system is disabled when the parking brake is disengaged.When the parking brake is disengaged, pilot oil pressure is available at port (1). The pilot oil pressure will move the spool in brake release sequence valve (4) against spring pressure. When the spool in brake release sequence valve (4) moves, oil will flow from the brake release system at port (2), through port (3) to the hydraulic tank. The brake release system is now disabled.When the parking brake is engaged, there is no pilot oil pressure available at port (1). Spring pressure moves the spool in brake release sequence valve (4) to the normally closed position. Ports (2) and (3) are now blocked. When the brake release system is activated, the oil from the brake release cylinder will disengage the parking brake.Recovery Hook
The sequence valve ensures that the brake release system is disabled when the engine is running.When the engine is running, pilot oil pressure is available at port (1). The pilot oil pressure will move the spool in brake release sequence valve (4) against spring pressure. When the spool in brake release sequence valve (4) moves, oil will flow from the brake release system at port (2), through port (3) to the hydraulic tank. The brake release system is now disabled.When the engine is stopped, there is no pilot oil pressure available at port (1). Spring pressure moves the spool in brake release sequence valve (4) to the normally closed position. Ports (2) and (3) are now blocked. When the brake release system is activated, the oil from the brake release cylinder will disengage the parking brake.