Case IH PUMA 130, Service Manual

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HYDRAULIC, PNEUMATIC, ELECTRICAL, ELECTRONIC SYSTEMS - PRIMARY HYDRAULIC POWER SYSTEM
BSE3845A
9
1. Power Beyond Ports
2. Pressure Relief Valve
NOTE: Semi Powershift transmission tractors have two shift buttons plus an extra range button on the reverse side
of the handle.
CLOSED CENTRE LOAD SENSING HIGH PRESSURE HYDRAULIC CIRCUIT
The principal of operation of the closed centre load sensing high pressure hydraulic circuit with variable flow piston
pump is to supply oil flow on demand. It also enables simultaneous operation of the trailer brakes, hydraulic lift,
remote control valve assemblies and front axle suspension where fitted. The load sensing variable flow piston pump
offers significant benefits in reducing the engine power loss that occurs in open centre systems where a high volume
of oil, often far in excess of demand, is continuously pumped round the hydraulic circuit even when they are not being
operated.
A fixed displacement pump (Charge Pump) serves as an initial displacement pump for the variable displacement pump
. The variable displacement pump first of all supplies oil to the trailer brake valve (where fitted), the remote valves
and electronic draft control valve and a pilot oil supply with lower priority. The highest load pressure is indicated to
the flow and compensating valve on the pump via the load sensing line. The flow and compensator valve controls
the pump pressure in such a way that it always exceeds the highest load pressure by a pre-set difference. A priority
valve for low pressure circuit demand is located in the bottom subplate of the remote valve stack. Tractors fitted with
Electro-hydraulic remote valves also have high pressure oil supplied from the variable displacement pump to the top
plate of the remote valve stack. The oil passes through the top plate via a small filter and a pressure limiting valve (
20 - 22 Bar ). The oil is then directed to the pilot oil supply of the electro-hydraulic control valve.
84479138A 06/06/2011
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