MAINTENANCE OF FORKLIFTS - OD1660 - LESSON 1/TASK 1
(2) Cleaning and Inspection.
(a) Clean the accumulator parts with cleaning solvent.
(b) Inspect the hose for deterioration and replace the hose if
defective.
(c) Inspect the piston for scores and scratches.
(d) Inspect the strap and body
for
cracks
or
any
damage.
Replace any parts that are defective.
(3) Testing the
Brake
Applicator
Valve
and
the
Differential
Pressure Switch.
(a) Before the brake valve is installed in the forklift, it
should be gage tested on the workbench to ensure that it is properly
assembled.
Brake pressure is the regulated accumulator pressure
allowed to pass through the valve when applying the brakes.
The
pressure is at maximum when the brake piston valve is completely
depressed.
Maximum pressure at the valve is controlled by shims
assembled beneath the operating piston. Shims are added to increase
the pressure, and they are removed to decrease the pressure. A 2,000
pound per square inch (psi) gage should be used to test the valve.
(b) When testing the valve, screw the gage into the brake port
on the valve. Fill the pump with hydraulic oil, and attach it to the
accumulator port on the valve. The valve should be pumped up to 1900
psi. The boot should be removed and the operating piston should be
depressed all the way in.
The gage should read 225-275 if the
correct brake line pressure is achieved.
(c) The accumulator pressure is the pressure of the oil in
the accumulator that is used for applying the brakes.
Accumulator
pressure is controlled by the pilot valve spring.
This is
purposely set below the steering relief valve pressure for
safety reasons, otherwise the components beyond the brake would
not operate.
After the brakes have been applied a number of
times, the pressure decreases to a low limit, at which time
the accumulator recharges.
The high limit is the adjustable
pressure, and once this is set, the brake valve design determines
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