Hydraulics
9803/3280 Issue 1
8 - 8 8 - 8
Circuit Descriptions
Section E Section E
Componet Key:
4A Slew Spool
4E Dipper Spool
4F Bucket Spool
4H ARV
4J ARV
4M ARV
4N ARV
4P ARV
4Q ARV (option)
Excavator Valve - Slew A.R.V. and Anti-
Cavitation Operation
The spool 4A is in neutral but the momentum of the slewing
excavator end creates back pressure in the head side of the
R.H. slew cylinder and in the rod side of the L.H. slew
cylinder. This opens A.R.V. 4J and dumps oil to exhaust. At
this point the cylinders cavitate and exhaust oil pressure
causes A.R.V. 4H to open, allowing oil from the exhaust
gallery to fill the L.H. cylinder.
Excavator Valve - A.R.V. Operation
The illustration shows the bucket spool 4F selected to
operate the service against an immovable object. This forces
the dipper away from the obstruction and pressurises the
head side of the dipper ram.
When this pressure reaches the setting of A.R.V. 4M, this
valve opens, relieving the pressure into the exhaust gallery.
Cavitation occurs in the rod side of the dipper service until
A.R.V 4N opens, allowing the higher pressure in the exhaust
gallery to supplement that in the service line.
Note: A.R.V. 4Q is only fitted to machines with a
Rockbreaker.
For a further detailed description, refer also to Pilot -
Operated Pressure Relief Valve Operation.
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