Komatsu PC88MR-10 Shop Manual page 235

6. When the pressure inside the work equipment cylinder is abnormally high, holding pressure of the work
equipment cylinder operates safety valve (4).
When there is a damage in the piping
1. When there is a damage in the piping (A) between the control valve and the work equipment cylinder,
chamber (a) and chamber (b) are disconnected.
2. The pressure of the work equipment is held to prevent the work equipment from sudden lowering.
When the pressurized oil flows from the control valve to the work equipment cylinder
When there is no damage in the piping
1. The pressurized oil which is led from the control valve to chamber (a) becomes higher than the combined
force of the pressure of chamber (b) of work equipment cylinder circuit and spring (6).
2. Check valve (5) opens, and chamber (a) and chamber (b) are connected
3. The pressurized oil flows from the control valve to the work equipment cylinder.
When there is a damage in the piping
1. When there is a damage in the piping (A) between the control valve and the work equipment cylinder, the
pressurized oil of chamber (a) leaks through the damaged part to the outside.
PC88MR-10
10 Structure and function
Anti-drop valve for arm
10-157