OPERATOR'S MANUAL MAINTENANCE

Section E - Hydraulics
Circuit Descriptions
Priority Valves
E-48 E-48
9803/9880-3
Priority Valves
For schematic,
K Fig 17. ( T E-49).
Boom over Slew Priority (A)
This is selected by the operator via switch in the right hand
console.
When operated the boom priority solenoid on the 8 spool
block 60 is energised sending a signal via port C6 to the
main control valve 14 at port Pi1. This selects the boom
over slew priority. Oil now being fed to the slew spool is
restricted to give priority to the boom.
Slew over Dipper Priority (B)
This is a non-selectable function automatically carried out
within the main control valve 14 when slew is used.
When Slew is selected a signal is sent from the servo
Shuttle valve 46 via port C8 to the main control valve 14 at
port Pc3. This selects slew over dipper priority valve B and
limits the flow to the dipper from pump P2 only. This makes
it possible to have maximum slew torque with high slew
pressure when the dipper is used at the same time.
Boom Priority over Bucket (C)
This a non-selectable function automatically carried out
within the Main control valve 14 when Boom up is selected.
When boom up is selected a signal is sent from port C1 on
the servo shuttle valve 46 to the main control valve port
Pi2. This selects the boom over bucket priority valve C. Oil
now flowing to the bucket spool is restricted and gives
priority to boom up.