Komatsu PC200-8M0 Shop Manual page 186

SEN06120-00
Boom hydraulic drift prevention valve
Function
While boom is not operated by the right work equipment control lever, the hydraulic drift prevention
q
valve prevents pressurized oil to leak from boom cylinder bottom through spool (1) to prevent the boom
from drifting hydraulically.
Operation
In boom "RAISE" operation
When operating boom "RAISE", the pressurized oil from the control valve exerts a left-hand force on the
q
right side of ring-shaped area (S), of which outside diameter is poppet (5) diameter (d1) and of which
inside diameter is seat diameter (d2).
q The left-hand force on area (S) compresses spring (4) and moves poppet (5) to the left.
q As a result, the pressurized oil from the control valve passes through the opening of poppet (5) and
flows to the boom cylinder bottom.
44
10-402
402 Hydraulic system, Part 2
Functions and operation by valve
PC200, 200LC, 220, 220LC-8M0