New Holland T7030 Service Manual page 46

DISTRIBUTION SYSTEMS - PRIMARY HYDRAULIC POWER SYSTEM
The Closed Centre high-pressure oil circuit works in the following way:-
The components of the high pressure oil circuit are connected via Load Sensing lines with the hydraulic Load Sensing
valve, which controls the capacity of the hydraulic pump.
If the trailer brake system, the remote valves, the hydraulic powerlift or the front axle suspension (where fitted) are
operated, the Load Sensing valve of the variable displacement pump compares the pressure in the Load Sensing line
of the components with the delivery pressure of the hydraulic pump.
If the pump pressure is less than the sum of the pressures of Load Sensing line and spring pressure on the oil flow
regulator, the pump capacity is increased. As soon as the demand of the oil circuit is fulfilled, the pump pressure
exceeds the sum of the pressures from Load Sensing line and spring pressure of the oil flow control valves. This
pushes the control pin in the oil flow control valve to the right, whereby the pilot oil is fed to the control cylinder of
the variable displacement pump swash plate, which reduces the pump stroke and thus adjusts the capacity to the
demand of the oil circuit.
A detailed description of the Load Sensing working principle of the axial piston variable displacement pump can be
found in Hydraulic pump - Static description (A.10.A).
High-pressure hydraulic system in Load Sensing version with closed circuit
See PRIMARY HYDRAULIC POWER SYSTEM - Hydraulic schema (A.10.A)
87628084B 12/06/2009
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