Komatsu PC500LC-10R Shop Manual page 333

10 STRUCTURE AND FUNCTION
When the pilot pressure (PU) is supplied (high pressure setting)
1.
During swing acceleration, the pilot pressure (PU) from the 2-stage swing relief solenoid valve acts on pres-
sure receiving area (d2 - d1).
2.
The spring (4) is compressed and its installed load increases, and the pump discharged volume is reduced
by the controller and the passage between valve (2) and valve seat (1) is choked.
By the above operation, the relief rate is reduced when the relief pressure is kept constant.
PC500LC-10R
COMPONENT PARTS OF SWING SYSTEM
10-239