TM 5-2420-231-10
0003
PRINCIPLES OF OPERATION - Continued
Hydraulic Power
The engine drives a hydraulic pump to provide hydraulic power to position the FEL or backhoe in several
directions. High hydraulic pressure is supplied to the hydraulic control valves. Low hydraulic pressure called pilot
pressure is supplied to the direction control lever, left backhoe control tower, and right backhoe control tower.
When the operator activates these controls, pilot pressure is directed to the corresponding hydraulic control
valves. Pilot pressure activates hydraulic control valves to allow high pressure hydraulic fluid to extend or retract
selected hydraulic cylinders which position the FEL or backhoe.
The FEL can be raised or lowered, tilted up or down, and opened or closed. The backhoe can swing from left to
right. The backhoe boom and dipper can be moved away from or toward the BHL. The backhoe dipper can be
tilted up or down. A hydraulic accumulator provides dampening for smoother FEL and backhoe operations.
Maximum hydraulic system pressure is regulated to prevent hydraulic hoses and seals from rupturing. Rear
backhoe-mounted auxiliary hydraulics allows uni-directional and bi-directional control of auxiliary equipment, such
as a hammer or an auger.
END OF WORK PACKAGE
0003-2