Counterbalance Valve Manifold - Komatsu 830E-AC Shop Manual

Counterbalance Valve Manifold

The counterbalance valve manifold (12, Figure 7-2)
is mounted at the rear of the pump/hoist valve mod-
ule. The counterbalance valve (13) controls the pres-
sure (like a relief valve) of the oil in the annulus area
of the hoist cylinders when the body approaches the
maximum dump angle. The valve restricts the maxi-
mum pressure build-up by relieving pressure in
excess of 20684 kPa (3000 psi), preventing possible
seal damage. Also see Figure 7-5 for a schematic
view of the counterbalance valve.
L07034
FIGURE 7-5. COUNTERBALANCE VALVE SCHEMATIC
Hoist Circuit
There are 2 pilot pressures that can open it (cylinder
head raise pressure & rod return pressure. If there is
no raise pressure, it will take 20684 kPa (3000 psi) of
rod end return pressure to open it. If there is theoreti-
cally 4592 kPa (666 psi) or more of raise pressure, it
is wide open for the return oil. In between these 2
maximums the ratio of raise:return pressure is 1:4.5
to open the return flow
Quick disconnect fittings (14) installed on the mani-
fold allow service personnel to dump a load in the
truck body if the engine, hoist pump, or other hoist
circuit component is inoperable, by connecting hoses
to the quick disconnects of an operable truck.
L7-7