11 - 1
Hose Burst Protection Valve
Boom & Dipper Operation
The small letter annotations
A
,
B, X
, and
Y
are stamped on
the valve.
Operation 1 - Load Raise
When 'dipper out' is selected, oil from the excavator valve
block is fed to port
B
, the oil opens check valve
C
against
spring
D
and passes through internal galleries into the rod
(raise) side of the ram via port
Y
.
Oil from the head side of the ram enters at port
X
, opens
check valve assembly
E
and returns to tank via port
A
and
the excavator valve block.
Operation 2 - Load Lower
Oil from the excavator valve block is fed to port
A
. The
connection to the head side of the ram is blocked by the
check valve assembly
E
and the position of spool
F
.
A cross drilling
G
in the valve connects the
A
port gallery to
cavity
J
. The pressure in cavity
J
increases to such a point
that it moves spool
F
to the left against the force of spring
H
.
The new position of the spool creates a connection between
the
A
port gallery and the head side of the dipper ram (via
port
X
).
There is also a connection between the
Y
port gallery and
the
B
port gallery. Oil from the rod side of the ram enters at
port
Y
and returns to tank via port
B
and the excavator valve
block.
Component Key:
C
Check Valve
D
Spring
E
Check Valve Assembly
F
Spool
G
Cross Drilling
H
Spring
J
Cavity
Section E
9803/3280
Section E
11 - 1
Issue 1
Circuit Descriptions
X
Y
A
B
BACKHOE VALVE
BOOM RAM
C
E
X
Y
A
B
BACKHOE VALVE
BOOM RAM
E
A323040
A323041