Komatsu Galeo PC138US-8 Shop Manual page 174

SEN02549-02
2. When boom and arm are set in neutral
Operation
If the control lever is returned to the neutral
q
position while the boom is raised out, the hold-
ing pressure in the boom cylinder bottom and
arm cylinder head is blocked by poppet (5) and
the pressurized oil flowing in through orifice (a)
is blocked by pilot spool (3). Accordingly, the
boom is held.
40
10 Structure, function and maintenance standard
PC138US, USLC-8