Terex TS14G, Maintenance Manual

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2
Section 235-0010
Bowl Hydraulic System - Hydraulic Lines and Fittings
SM 1894 1-00
The apron cylinders are actuated by the apron control
lever on the servo valve. Oil flows into and out of the
apron cylinders to raise or lower the apron.
When the servo control apron lever is pushed into the
'LOWER' position, a passage in the control valve is
opened and oil flows from the pump into the control
valve. Oil from the control valve flows into the apron
cylinder rod ends. The oil pressure in the cylinder rod
ends, forces the piston rods to retract. As the piston
rods retract, the apron arms are pulled back causing
the apron to power down. As the apron cylinders are
retracting, any oil trapped in the base ends is forced
out through the control valve and back into the tank.
To raise the apron, the servo control bowl lever is
pulled into the 'RAISE' position. This shifts the control
valve apron spool into the raise position. Oil leaves
the control valve and flows into the apron cylinder
base ends. Oil pressure extends the cylinders which
raises the apron. Any oil trapped in the cylinder rod
ends is forced through the control valve and back to
the tank.
Ejector
The scraper ejector is operated by the ejector
cylinder which is mounted to the tail assembly of the
scraper and to a lever that is hinged at one end to the
upper cross member of the bowl. The lower end of
this lever has a roller which rolls on a wear plate
welded to the ejector.
The oil which flows into and out of the ejector cylinder
is the same as that for the apron and bowl cylinders.
The ejector cylinder is actuated by the ejector control
lever on the servo valve. As the cylinder is extended, a
force is transmitted to the ejector through the lever and
roller which causes the ejector to pivot forward. The
ejector is returned to the 'LOWER' position by the
force of its weight creating an opposite action on the
lever and cylinder. A detent mechanism in the servo
valve holds the ejector control spool in the 'LOWER'
position, allowing the ejector to 'FLOAT' down to the
loading position, after the material is dumped from
the bowl, without further attention from the operator.
The control lever will remain in the 'LOWER' position
until manually moved to the 'NEUTRAL' position.
TIMING TEST
As a general field test, the correct operation of the
hydraulic system can be checked by timing the lift of
the scraper bowl. If the scraper bowl can be lifted in
the correct time, it can be assumed that the ejector
and apron are operating at peak efficiency.
The test should be performed with the scraper bowl
empty and blades resting on the ground, the engine
and hydraulic oil heated to normal operating
temperatures, and the engine running at top rev/min.
With these conditions, the scraper bowl should be
raised to its fully raised position in 5.8 seconds.
If the timing test is in excess of 5.8 seconds, check
the following items in sequence:
1. Check oil level in the tank.
2. Visually check for apparent leaks, faulty pump,
cylinders or control valves.
3. Check pivot mechanism for binding.
4. Check hydraulic oil pressure/relief valve
adjustment (see below).
CHECKING AND ADJUSTING RELIEF
VALVE PRESSURE
The relief valve, incorporated in the control valve, is
set at the factory for a maximum oil pressure of
127.5 bar (1 850 lbf/in
2 ). Do not adjust the valve
setting unless it has been determined that the
maximum pressure is above or below 127.5 bar
(1 850 lbf/in
2 ).
Note:
Do not change the setting to increase pressure
above 127.5 bar (1 850 lbf/in 2 ) to compensate for
over loading the scraper with extra heavy materials.
To check the relief valve adjustment, the bowl must
be empty, hydraulic oil and engine at normal
operating temperatures. Remove cap from connector
or plug in the face of the control valve and install a
207 bar (3 000 lbf/in
2 ) capacity pressure gauge.
Operate the engine at 1 500 rev/min and raise the
bowl until the related cylinders are fully extended.
Hold the bowl control lever in the raise position and
keep the engine accelerated at 1 500 rev/min while
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