McHale HS2000 Round Bale Wrapper
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5.7 HS2000 set-up & tractor hydraulic system
Open centre
This is the most common system on smaller tractors (i.e. less than 60 kW) and 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, the output flow will be
max. 60 l/min and is usually not adjustable.
Closed centre
This system is found on older John Deere models (i.e. pre 00 and 10 series) and on
some other makes and particular models. In this system, no oil flows through the
control valve when the machine is idle but it maintains maximum oil pressure in the feed
line. The tractor will have a fixed displacement pump and the output flow is usually not
adjustable.
Load-sensing with Power Beyond fitted
This is the preferred hydraulic system. This system is found on most, but not all, newer
tractors. 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.
Ideal configuration
In its most ideal configuration, the tractor will have a Power Beyond connection,
whereby the oil comes direct from the pump, by-passing the tractor auxiliary valves to
a female
½” quick release connection, which becomes the main feed.
It will also have a third 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 the most efficient hydraulic system available as the
control valve now controls the amount and the 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 HS2000 with a load-sensing system via. the
tractor auxiliary spools (i.e. continuous oil flow, where the control valve is set to open
centre setup and flow is set to 60 l/min. from the tractor), McHale do not recommend
operating in this setup as controlling the oil flow is too variable from one tractor to
another and there is a 20 kW PTO power loss associated with the overheating of oil.
CAUTION: It is important to determine the correct hydraulic
system on the tractor
Incorrect setup will cause serious damage to the tractor’s hydraulic
system or, at least, excessive heating of the oil.
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