Multi Pro 5800 Hydraulic SystemPage 5 − 13
Steering Circuit
A two (2) section gear pump is coupled to the piston
(traction) pump. The front gear pump section (closest to
the piston pump) supplies hydraulic flow to the spray
pump drive circuit. The rear gear pump section supplies
hydraulic flow to both the steering and spray boom lift/
lower circuits. Hydraulic pump flow from the rear pump
section is routed to the steering control valve first so the
steering circuit has priority. The gear pump takes its suc-
tion from the hydraulic reservoir. Steering and boom lift/
lower circuit pressure is limited to 1015 PSI (69 bar) by
a relief valve located in the gear pump.
The steering control valve includes a check valve that al-
lows steering operation when the engine is not running.
Steering wheel rotation with the engine off results in oil
flow from the steering control gerotor. The check valve
opens in this situation to allow oil flow from the steering
control to the steering cylinder in a closed loop.
Steering circuit pressure can be measured by installing
a pressure gauge to the test port fitting at the gear pump
outlet. Hydraulic flow for the steering circuit can be moni-
tored at the outlet of the rear gear pump section.
No Turn (Fig. 9)
With the steering wheel in the neutral position and the
engine running, gear pump flow enters the steering con-
trol valve (port P) and goes through the steering control
spool valve, by−passing the rotary meter and steering
cylinder. Flow leaves the control valve (port E) and is
routed to the boom lift valve, oil filter and finally returns
to the hydraulic oil reservoir.
Left Turn (Fig. 9)
When a left turn is made with the engine running, the
turning of the steering wheel positions the spool valve so
that flow goes through the bottom of the spool. Flow en-
tering the steering control valve from the gear pump
goes through the spool and is routed through the rotary
meter (V1) and out the L port. Pressure extends the
steering cylinder for a left turn. The rotary meter ensures
that the oil flow to the cylinder is proportional to the
amount of the turning on the steering wheel. Fluid leav-
ing the cylinder flows back through the spool valve, then
to the oil cooler and returns to the reservoir.
The steering control valve returns to the neutral position
when turning is completed.
Right Turn (Fig. 9)
When a right turn is made with the engine running, the
turning of the steering wheel positions the spool valve so
that flow goes through the top of the spool. Flow entering
the steering control valve from the gear pump goes
through the spool and is routed through rotary meter
(V1) and goes out port R. Pressure retracts the steering
cylinder for a right turn. The rotary meter ensures that
the oil flow to the cylinder is proportional to the amount
of the turning on the steering wheel. Fluid leaving the
cylinder flows back through the spool valve, then to the
oil cooler and returns to the reservoir.
The steering control valve returns to the neutral position
when turning is completed.
Hydraulic
System
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