Directional Control Valve
The directional control valves are pilot-operated,
the opposite end of the valve spool. This flow
four-way, three-position valves with either an open or
pattern is applicable in either direction the valve may
closed spool. Whether a valve has an open or
be positioned. If it is necessary to open more than
closed spool is determined by whether, with the
one directional control valve in the same valve bank,
spool in the neutral position, the work ports are open
it may be required to partially close or feather the
to the reservoir return passage. If the work ports are
valves that are located in the bank first, in reference
open to the reservoir return passage, the valve is
to flow from the pump, in order to provide sufficient
classified as an open spool-type; if they are not, the
flow to the valves located last in the bank.
valve is a closed spool-type. (Refer to the Valve
Usage Table for circuit applicability by valve type.)
The closed spool directional control valve functions
Additionally, the valve spool is spring-loaded to the
basically the same way as the open spool directional
control valve, in that the through passage of the
valve must be blocked off by the valves' spool to
The open spool directional control valve is
divert flow to the dead end parallel passage. With
constructed with a through passage to allow flow to
flow diverted to the parallel passage, pressure than
pass to the next valve(s) in the bank and on to the
must unseat the load check valve to allow the flow to
reservoir, when the valve spool is in the neutral
reach the open work port. The load check valve is
position. By positioning the valve spool to a work
provided to prevent back sliding of components
position, the through passage is blocked and flow is
which support heavy loads as is evidenced by the
diverted o the dead end parallel passage. This
circuits this valve is used in. Return flow from the
causes flow to be directed to the component's open
component is through the return work port to the
supply work port. Return flow is routed from the
reservoir return passage.
return work port to the reservoir return passage by
Remove the valve cover, if applicable.
Position the valve bank onto the turntable and
secure it in place with the bolts and nuts, Refer to
Tag and disconnect the hydraulic lines running
to the directional control valve bank, refer to Figure
Connect the electrical leads to the valve bank
as tagged during removal.
Tag and disconnect any electrical leads from
the valve bank.
Connect the hydraulic lines to the valve bank
as tagged during removal.
Remove the bolts and nuts securing the valve
bank and remove the valve bank.