SECTION 7 – HYDRAULICS
3120933 Rev. 0
USTC
7-1
HYDRAULIC SYSTEM SAFETY
It should be particularly noted that the machine’s
hydraulic systems operate at extremely high and
potentially dangerous pressures. Every effort should
be made to relieve any system pressure prior to dis-
connecting or removing any portion of the system.
Relieve system pressure by cycling the applicable
control several times with the engine stopped and
ignition “on” to direct any line pressure back into the
return line to the reservoir. Pressure supply lines to
system components can then be disconnected with
minimal fluid loss.
WARNING: NEVER CHECK FOR LEAKS
USING HANDS. HYDRAULIC FLUID UNDER
PRESSURE CAN PENETRATE SKIN. NEVER
CHECK FOR LEAKS USING HANDS.
DRIFT TEST
To determine if cylinders are leaking internally, drift
tests can be conducted on the telescope and lift cylin-
ders.
Telescope Cylinder
1. Activate hydraulic system, properly set outrig-
gers and stabilizers.
WARNING: BEFORE EXTENDING AND
RAISING BOOM, ENSURE THAT AREAS
ABOVE AND BELOW BOOM AND HOOK
BLOCK, AND AHEAD OF HOOK BLOCK ARE
CLEAR OF ALL OBSTRUCTIONS AND
PERSONNEL.
2. With boom in the stowed position, move tele-
scope control lever forward until boom extends
approximately four feet. Use tape or chalk line
to mark outer-mid section at end of base section.
3. Raise boom to maximum elevation (80°).
4. Shut down hydraulic system by disengaging
Power-Take-Off (PTO) and turning off truck
engine.
5. With engine off, move telescope control lever to
retract boom. If boom starts to retract, holding
valve is defective and requires replacement.
6. If boom does not retract, complete steps 7
through 10.
CAUTION: HYDRAULIC LINES AND
PORTS SHOULD BE CAPPED IMMEDIATELY
AFTER DISCONNECTING LINES TO AVOID
THE ENTRY OF CONTAMINANTS INTO THE
SYSTEM.
7. Tag and carefully disconnect the hydraulic lines
to telescope cylinder. Use a suitable container to
retain any residual hydraulic fluid. Immediately
cap lines and ports.
8. Leave boom elevated in test position for ap-
proximately one hour.
WARNING: BEFORE LOWERING BOOM,
ENSURE THAT AREAS BELOW BOOM AND
HOOK BLOCK ARE CLEAR OF ALL
PERSONNEL AND OBSTRUCTIONS.
9. Start engine and, using truck hydraulics, lower
boom to horizontal position.
10. Check boom length against original measure-
ment.
If boom has retracted more than one inch and oil
is leaking around rod-end of telescope cylinder
(check with light and inspection mirror), seals
are defective. Replace the seals and check the
cylinder rod for scoring.
If boom has retracted and oil is leaking from
holding valve, the valve is either improperly
adjusted or defective and requires replacement.
11. Connect hydraulic lines to telescope cylinder.
Содержание 2500 jbt
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