TM 9-4940-568-34
3-4
3-3.
CRANE PRINCIPLES OF OPERATION (Continued)
When the main control valve is activated, the
ports open. Depending on the direction that
the control valve lever is moved, one port
directs hydraulic oil to push its cylinder in the
desired direction. The other port allows the
hydraulic oil in the other end of its cylinder to
return to the reservoir. When the control valve
lever is moved in the opposite direction, the
function of the ports is reversed.
The hoist circuit has a preset relief valve that
further protects its function.
The FRS also has a main relief valve in the load
sense circuit, to protect all components of the
hydraulic system.
