OPERATOR'S MANUAL MAINTENANCE

Section E - Hydraulics
Circuit Descriptions
Neutral Circuit
E-30 E-30
9803/9880-3
Neutral Circuit
For Schematic,
K Fig 8. ( T E-31).
With all the controls in the neutral position, flow from pump
1 enters the main control valve 14 at port P2 and flow from
pump 2 enters the main control valve 14 at port P1.
Oil is allowed to flow across all of the spools via the neutral
gallery when all controls are in the neutral position. Oil from
pump 1 exits port Ps2 and oil from pump 2, exits port Ps1
at the top of the main control valve.
Both flows of oil meet a separate restrictor and relief valve.
Some oil will pass through the restrictor above 40 bar and
back to tank, creating back pressure in the line. Oil is
exhausted across the negative controls relief valves at 40
bar (580 Ib in
2
). The back pressure created is sent to ports
Pi1 and Pi2 negative control ports on the pumps to keep
the pumps at minimum flow.