11 - 8
Hose Burst Protection Valve
Loader Operation (Cont’d)
Operation 3 - Relief Valve
If during normal operation the pressure in the ram increases
(for example, by the operation of the bucket against an
obstacle), increasing pressure in the ram enters the HBPV at
C2 and will be sensed on the face of plunger J. When the
force of spring H is exceeded, the plunger is made to move
off its seat thus allowing oil to flow through the valve to port
V2.
Note: Oil exhausted via port V2 will not reduce to low
pressure until the A.R.V. in the valve block 9 also opens.
Operation 4 - Hose Burst Condition
In the event of a hose burst or other leakage in the feed to
the HBCV, plunger J will be held on its seat by the force of
spring H. Also, back pressure and the force of spring B will
hold check valve seat A firmly against the plunger, thus
trapping a column of oil in the head side circuit which will
prevent the load from dropping.
Note that before the plunger can move onto its seat, the
pressure on the pilot side of the piston G must vent to
atmosphere quickly, therefore ball L will open against the
force of spring K which allows the oil to vent down the
threads AND through the drilling previously plugged by ball
L.
Section E
Hydraulics
9803/3280
Section E
11 - 8
Issue 1
Circuit Descriptions
Component Key:
A Check Valve Seat
B Spring
G Piston
H Spring
J Plunger
K Spring
L Ball
9 Loader Valve Block
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