McHale
Fusion Vario
Baler & Wrapper
42
5.7 Machine set-up & the tractor hydraulic system
There are 3 systems found on tractors, as outlined below:
1.
Open-centre
: This is the most common system on smaller tractors (less than
60 kW) and also on some bigger older tractors. In this system, all the oil flows
through the control valve, when the machine is idle. The tractor will have a fixed
displacement pump and the output flow will be max. 60 l/min and flow is usually
not adjustable.
2.
Closed-centre
: Although not so common on today’s tractors, this system is still
found on the older John Deere models (pre. 00 & 10 series), but also on some
other makes and particular models. In this system, no oil flows through the
control valve, when the machine is idle, but maintains max. oil pressure in the
feed line. The tractor will have a fixed displacement pump and the output flow
is usually not adjustable.
3.
Load-sensing with ‘Power Beyond’ fitted
: This is, by far, the preferred
system. Most newer tractors are done this way, but not all. In this system, no
oil flows through the control valve, when the machine is idle, but it maintains a
low oil pressure in the feed line, (approx. 21 bar). The tractor will have a
variable displacement pump and will always have some means of adjusting the
oil flow on each auxiliary valve.
In its most ideal configuration, the tractor will have a ‘Power Beyond’ connection, i.e.
oil comes direct from the pump, by-passing the tractor auxiliary valves, to a ‘female ¾”
quick-release’ connection, which becomes the machine feed.
It will also have a 3
rd
connection to the tractor, called the pilot sensing line, and this pipe
sets the correct oil flow for the tractor to pump for each operation.
This is the most advanced and efficient hydraulic system available, as the machine
control valve now controls the amount & pressure of oil required for each control valve
operation, and only the correct amount is pumped. This will save up to 20 kW PTO
power on the tractor.
Although it is possible to operate the machine with a load-sensing system via the
tractor auxiliary spools, i.e. continuous oil flow (control valve is set to open-centre setup
and flow is set to 45 l/min from the tractor).
McHale
do not recommend operating the
machine in this setup, as controlling the oil flow is too variable from one tractor to
another, and there is also a 20 kW PTO power loss with it’s associated over heating of
the oil.
Once the correct tractor system is identified, use the map in the next section, to select
the best setup for the machine.
CAUTION: Hydraulic system setup
It is very important to determine the correct hydraulic system on the
tractor, as a wrong setup will cause serious damage to the tractor
hydraulic system, or at least excessive heating of the oil.
