The holding valve is ported to allow hydraulic flow in
hydraulic circuit. As the directional control valve is
two directions. To raise a load, the oil must unseat the
opened to the lower position, pressure is applied to
free flow poppet valve. In this case, oil pressure must
the pilot piston. The pilot piston moves against the
overcome the main poppet spring. To do this, the oil
pilot release poppet until it unseats the pilot release
flows through the oil ports of the pilot release poppet
poppet valve which port oil to the return side of the
valve which applies pressure to the inside face of the
directional control valve.
free flow poppet. When the main poppet unseats, the
oil flows past the main poppet seat to the component
The free flow check valve is provided for venting the
to be worked.
pressure side of the pilot piston.
When a load is to be lowered, as in retracting the
A vent is provided for venting the area between the
boom, better control is necessary because of the
pilot piston O-rings should weepage occur. A second
weight of the load. For this reason a pilot pressure is
vent is provided at the adjustment end of the pilot
used for positioning the main poppet valve which is
release poppet valve should weepage occur past the
being held against its seat by heavy springs. The pilot
O-ring seal into the spring area.
pressure is sensed from the lowering side of the
Do not remove the adjustment screw or
I t is recommended that all O-rings and
locknut during disassembly.
1. Remove plug, with adjustment screw, from
valve body by turning large nut of plug counter-
1. Install all backup rings and O-rings onto valve
clockwise. Do not remove adjustment screw or
locknut from plug.
2. Install ball and spring in poppet and secure with
Remove O-ring from plug.
Remove spring and seats from valve body.
3. Coat poppet with clean hydraulic oil and install
poppet into valve body.
Remove poppet from valve body.
Install seats and spring into valve body.
Remove plug, spring, and ball from poppet.
5. Install O-ring onto plug and install plug, with
6. Remove O-rings and backup rings from valve
adjustment screw, into valve body.