Operation and maintenance manual

Section 220-0000
SM 1390 Rev 2 2-02
3
SM - 1335
Fig. 2 - Assembly of Typical ORFS Connector
'O' RING
'O' RING
SLEEVE
TUBE
FITTING
NUT
bearings permit a limited amount of cylinder misalignment
when travelling over rough terrain.
Pressure Test Point
A diagnostic pressure test point, located in the
manifold at the rear left hand side of the tractor frame,
provides a quick and easy method of checking steering
system pressure. The pressure is taken from a tee at
port 'PP' of the flow amplifier valve. System pressure is
206 bar (3 000 lbf/in
2
).
'O' RING FACE SEALS (ORFS)
Where hydraulic lines are fitted with ORFS
connections, the following procedure should be carried
out during installation. Refer to Fig. 2.
Steering System - Steering System Schematic
System relief valve is set to control maximum working
pressure in the steering system to 206 bar (3 000 lbf/in²).
Priority spool directs oil supply from the pump when
engine is running, to steering valve port 'P' and through
the 'EF' passage to the body control valve.
Shock & anti-cavitation valves limit shock pressures in
the steering cylinders to 241 bar (3 500 lbf/in²). The
shock valves sense cylinder shock pressure when
there is no steering taking place. Shock pressure is
absorbed in the cylinder circuit and is not transmitted
to the steering valve. The anti-cavitation part of the
valve prevents cavitation in the cylinder circuit.
Amplifier spool controls the amount of oil flowing into
the directional spool 'HP' passage.
Directional spool when moved in either direction
against the return springs, sends oil pressure to the
steering cylinders for right or left turns.
Various orifices, orifice drillings and check valves are
located within the valve assembly.
Steering Valve (7)
Refer to Section 220-0190, STEERING VALVE.
The steering valve is connected to the steering
column and controls hydraulic flow in the steering
system. A pressure relief line in the neutral position,
between steering cylinder ports 'L' & 'R' and tank
return port 'T', means that the steering valve must
only be used with flow amplifier valve (5).
Steering Cylinders (8)
Refer to Section 220-0120, STEERING CYLINDER.
There are two single stage, double acting, cushioned
steering cylinders on the vehicle. The cylinder base
end is connected to the front frame and piston rod
end is connected to the rear frame. Single stage,
double acting means that the piston rod can have oil
applied to either side, extending or retracting the
piston rod.
The cushioning effect is obtained by a tapered spear
at the base end of the cylinder body entering a cavity
in the piston rod through a cushioning sleeve. This
gradually slows the piston which in turn helps to control
destructive shock effects when the piston bottoms.
Cylinder mounting is by pins through spherical bearings
in the cylinder base and piston rod ends. The spherical
a. Ensure 'O' ring/seal is in place and that joining
surfaces are clean. If necessary, retain 'O' ring/seal in
place with a light coating of grease or vaseline.
b. Initially, the nuts should be tightened by hand.
c. Where a hose is fitted, ensure that it is not twisted
or kinked when the nuts are tightened so that it is
allowed to adopt a natural position.
d. Where a tube is fitted, ensure that the connection is
aligned correctly.
e. Tighten the nut a further 1/4 to 1/2 a turn using the
correct size of spanner (wrench).
f. Check that a satisfactory hose or tube routing has
been achieved.
FILLING AND BLEEDING THE STEERING
SYSTEM
1. Fill hydraulic tank to maximum level. Be ready to
add oil when the engine is started. Do not let oil drop