Komatsu PC200-8M0 Shop Manual page 194

SEN06120-00
Main relief valve
1. Spring
2. Poppet
Function
q This valve has two selectable settings for its set pressure.
q If the extra power is necessary, this valve is set to the high-pressure setting when pilot pressure (P) is
applied to it from the 2-stage relief solenoid valve.
q The relief valve set pressure is determined by the load at installed length of spring (1). (1st stage set
pressure)
When the 1st stage set pressure is set correctly, the 2nd stage set pressure does not need to be set.
q
Setting the 1st stage set pressure completes the setting of the 2nd stage set pressure.
Operation
When pilot pressure (P) is shut off (low pressure setting)
q The set pressure is determined by the load at installed length of spring (1).
When pilot pressure (P) is supplied (high pressure setting)
The load at installed length of spring (1) is added with the force exerted by pilot pressure (P) applied to
q
the area of diameter (d1) of poppet (2), raising the set pressure to higher level.
52
10-402
402 Hydraulic system, Part 2
Functions and operation by valve
PC200, 200LC, 220, 220LC-8M0