CYLINDER AS 1772598 - Caterpillar

Illustration 1 g00584424
Location of the makeup valve for the piston motor for the fan drive (1) Supply line from the piston pump for the fan drive (2) Makeup valve for the piston motor for the fan drive (3) Return lineThe makeup valve (2) for the piston motor is mounted on the fan support structure below the fan.
Illustration 2 g00537842
Makeup valve for the piston motor for the fan drive (1) Supply port from the cooling piston pump (3) Return port (4) Passage (5) Spring (6) Check valve (7) PassageReturn oil from the piston motor is used as makeup oil. When the fan stops operating, the makeup oil is used to prevent a vacuum condition in the piston motor.When the control valve for the piston pump signals the piston pump to destroke, the supply of oil to the piston motor is reduced. The piston motor continues to rotate due to the mass of the fan blade assembly. Continued rotation of the piston motor creates a vacuum at passage (4) of makeup valve (2). This vacuum lowers the pressure in passage (4). The combined force of the pressure in passage (4) and the force of spring (5) is less than the force of the pressure that is in passage (7). Check valve (6) will open.When check valve (6) is open, return oil from passage (7) flows to passage (4). The return oil enters the piston motor through line (1). This makeup oil circuit eliminates the possibility of cavitation in the piston motor.The same process occurs when the machine is shut down.