Theory of Operation
at the flow regulating valve to the arm head end
Actuating a pilot controller to operate a dig or propel
reduced leakage pilot valve (L).
function sends pilot oil to the pilot cap (1--12) of a
· Arm-in--pilot oil flows from the pilot cap (4) to the
control valve spool shifting the spool(s). The pilot oil
arm rod end reduced leakage pilot valve (N), the
also flows to other valves for the following functions:
bucket flow control pilot valve A (H), and through an
· Boom up--pilot oil flows from the pilot cap (1) to the
orifice to the hydraulic oil tank.
propel flow control valve (Q) and the bucket flow
Orifices in the top pilot caps allows a small amount of
control pilot valve A (H). If arm-in is actuated, pilot
pilot oil to flow to the warm-up and air bleed circuit (J)
oil flows through pilot valve A to the bucket flow
and back to the hydraulic oil tank. The flow of oil
control pilot valve B (B).
· Boom down--pilot oil flows from the pilot cap (2) to
removes any air trapped in the top pilot cap and to
provides a flow of warm-up oil when functions are not
the boom reduced leakage pilot valve (E) and
actuated. (See Warm-Up Circuit Operation in this
through an orifice to the hydraulic oil tank.
· Arm-out--pilot oil flows from the tee connection (3A)