Komatsu PC88MR-10 Shop Manual page 169

Boom regeneration circuit
When boom lowers under its own weight
Function
While the boom is lowered, if bottom pressure (A) of cylinder (1) is higher than head pressure (B) and the
boom lowers by its own weight, the return flow on the bottom side is supplied to the head side to increase
the cylinder speed.
Operation
If the boom lowers by its own weight during the boom LOWER operation, bottom pressure (A) of boom
cylinder (1) is higher than head pressure (B).
A part of return flow from the bottom side flows through regeneration passage (a) of boom spool (2) to the
head side by pushing check valve (3) to open.
The boom lowering speed is increased.
PC88MR-10
(PC88MR-L511-040-K-00-A)
10 Structure and function
Control valve
10-91