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Section E
24 - 1
Ram Creep Tests - All Services
If ram creep is suspected the following procedures must be
carried out to define if the leakage is within tolerance. Ram
c reep c an b e c aused b y a num b er o f reaso ns:
Cylinder/Piston Leakage, Spool Leakage, ARV Leakage.
The text and illustrations show a typical ram installation (in
this instance the boom ram), the principle applies to all
rams.
Note: The procedures are not applicable for rams fitted with
hose burst protection valves.
! WARNING
Hydraulic fluid at system pressure can injure you. Before
disconnecting or connecting hydraulic hoses, stop the
engine and operate the controls to release pressure
trapped in the hoses. Make sure the engine cannot be
started while the hoses are open.
INT-3-1-11/1
! WARNING
Take care when disconnecting hydraulic hoses and
fittings as the oil will be HOT.
TRANS 1-2
A Test for Ram Creep
1 Operate the machine to bring the hydraulic oil to a
normal working temperature of 50° C (122° F) which can
be measured using a hydraulic oil temperature probe
(service tool 892/00285).
2 Fit an appropriate pressure gauge A to a tee-piece in the
service hose which is pressurised when the ram in
question is supported (Fig 1).
A
C
9803/3280
Hydraulics
Service Procedures
C
B
FIG 1
380190
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3 Operate the rams to ensure they are full of hot oil.
4 Apply a load to the suspect ram for example the boom
ram by raising the dipper to the horizontal as at B.
5 M easure t he ac t ual p ist on rod movement over 10
minutes. Measure the movement by checking the pivot
pin to pivot pin dimensions as at C. Alternatively mark
the rod with a felt tip pen 150mm (5.9 in) from the end
cap and check the movement after 10 minutes, this is
not possible on the majority of boom/extending dipper
rams.
6 Using Table 1, check if the piston rod movement is within
the recommended tolerance. If so, the ram creep is
acceptable.
Note: The table indicates the MAXIMUM permitted ram
movement.
7 If the rate of movement is unacceptable, identify if the
fault is as a result of cylinder/piston leakage or spool
leakage at the control valve, see procedure B and C.
Section E
24 - 1
Issue 1
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