51 - 3
Section D
Controls
9803/3280
Section D
51 - 3
Issue 1
Precision Control (Servo)
Servo Pressure Supply Valve
Dismantling and Assembly
Dismantling
The illustration shown on the opposite page is intended as a
guide to dismantling. Be sure to note the location of all
components when dismantling. Although some components
may appear to be identical they are not interchangeable.
Make sure that components are assembled in their original
positions.
Great care should be taken when dismantling and
assembling a valve to avoid the following:-
• Contamination
• Damage to spools
• Damage to seal grooves
Any of the above may result in possible problems with the
operation of the valve.
1 Remove the servo pressure supply valve from the
machine, refer to Servo Pressure Supply Valve -
Removal and Replacement.
Note: The illustration depicts a complete strip down, but to
carry out specific servicing/repairs, e.g. renewal of one of the
solenoids, it is only necessary to dismantle the relevant
components.
Assembly
Assembly is the reverse of the dismantling sequence.
1 Clean the valve components in an appropriate solvent.
2 Renew all 'O' rings and back-up rings.
3 Lubricate parts with JCB Hydraulic Fluid before
assembling. Make sure that all the parts move freely.
Torque Settings
Item Nm kgf m lbf ft
1 100 10.2 73.8
2 10 1 7.4
2A 10 1 7.4
2B 30 3 22.1
3 100 10.2 73.8
4 100 10.2 73.8
5 150 15.3 110.6
6 100 10.2 73.8
7 15-20 1.5-2 11-14.8
Accumulator
The accumulator 1 can be removed as shown. Take great
care when handling the accumulator, the unit is pre-charged
with nitrogen gas and further dismantling of the accumulator
should not be attempted. The adaptor assembly 3
incorporates a non-return valve with a spring and ball as
shown.
Regulating Valve Assembly
The regulating valve assembly 5 can be removed as shown.
The valve is non-adjustable and is factory set with shims.
Take care to keep all the shims together.
Pressure Relief Valve
The pressure relief valve 6 can be removed as shown.
Solenoid Isolation Valves
The solenoid isolation valves 7 can be removed as shown. It
is possible to remove the valve cartridges for cleaning or
resealing without removing the complete valve from the
machine. If there is evidence of damage to the valve or its
seat caused by debris then the cartridge must be renewed.
Note: If removing components from a valve block that is
fitted on a machine the pilot circuit accumulator pressure
must be vented first. With the operator seat locked in the
rear facing position and with the arm rests raised forward
(for backhoe operation), switch the starter to ON without
starting the engine. Operate the joystick controls several
times to vent the hydraulic pressure from the servo system
and backhoe rams. Turn the starter switch to the OFF
position and remove the key.
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