6
6-1 THE HYDRAULIC SYSTEM
There are really two separate hydraulic
systems. The hydraulic tandem pump contains
two sections that draw oil from the tank through
two 100-mesh screen filters located inside the
tank. Each section pumps oil into one of the two
4-way control valves. The valves can be
electrically or manually controlled. The two
valves, in turn, control two separate 10” cylinders.
To raise the lid, pull the valve handle
toward you, oil is then sent to the bottom port of
the cylinder, which will force the lid to go up. The
oil in the top of the cylinder is sent through a 10-
micron filter and then to the tank
To lower the lid, push the valve handle
away from you, oil is then sent to the top port of
the cylinder, which will force the lid down. The
oil in the bottom of the cylinder is sent through a
10-micron filter and then to the tank.
When the valve handles are in the center
position oil is sent through a 10-micron filter and
then back to the tank.
There are two safety pressure valves
located on each system. A Main Relief on the
control valve restricts the valve operating pressure
to 2600 psi. The Cylinder relief valves restricts
the cylinder operating pressure to 2800 psi and
protects the cylinders from extreme pressures that
could damage them.
6-2 STANDARD SPEED CYLINDER OPERATION
On our standard hydraulic system, to raise the lid we pump 32 gallons of oil into the bottom
of each cylinder. The 27 gallons of oil in the top goes back to the tank. The 5-gallon difference is
equal to the area of the rod.
To lower the lid we pump 27 gallons of oil into the top of each cylinder. The 32 gallons of oil
in the bottom goes back to the tank.
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