Theory Of Operation - Doosan DX140R Shop Manual

Theory of Operation

Service Spool Movement
Remove the stopper plug of both pilot caps before using this
section.
When necessary, replace the shut-off valve with an overload
relief valve and remove the plug at port (P4).
When the spool is moved by being pressurized through the pilot
port (pb2) (pa2) of the first service (Section 2), the neutral path
(L1) will be closed. The oil supplied through port (P1) flows
through the parallel path (L3) load check valve (S2-1), path (S2-
2), and spool head to port (B2) (A2). Lubricant oil returns from
(A2) (B2) to the tank path Ta via the spool head.
This section makes use of the load check valve which allows
external joining at the (P4) port.
Figure 2
SP001029
Main Control Valve
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