JLG G12-55A Service Manual - Manual (Page 65)

3-29 G10-55A, G12-55A
Boom
3.12 FORKS
Forks should be cleaned and inspected prior to being
attached to carriage. If the following criteria is not met,
forks must be removed from service immediately.
Daily Inspection
1. Inspect forks (1) for cracks, paying special attention
to heel (2) and mounting tubes (3).
2. Inspect forks for broken or bent tips (4) and twisted
blades (5) and shanks (6).
Yearly Inspection
1. Straightness of the upper face of blade (5) and the
front face of shank (6) should not exceed 0.5 percent
of the length of blade or height of shank.
2. Angle (7) between upper face of blade and front face
of shank should not exceed 93 degrees.
3. Thickness of blade (8) and shank (9) should not be
reduced to 90 percent of original thickness.
Note: Contact local distributor with fork part number to
find manufactured dimensions of fork blade.
4. Ensure that the fork length (10) is adequate for
intended loads.
5. The Fork markings should be legible, re-stamp
markings if required.
6. Compare fork tips (11) when mounted on a carriage.
Maximum difference in height of fork tips is 3 percent
of the length of the blade (10).
3.13 EMERGENCY BOOM LOWERING
PROCEDURE
3.13.1 Equipment and Supplies Required
Auxiliary Hydraulic Power Supply:
• Portable hydraulic unit or another machine with
an auxiliary hydraulic power supply with a
capacity to hold up to 22 gal (83 L) of hydraulic
oil from the machine during lowering process.
Note: If another machine is being used, the hydraulic
reservoir must be drained to accept a minimum of 22 gal
(83 L) of hydraulic oil before attempting this procedure.
• Standard Mechanic Tools.
MH6460
3
2
6
7
5
1
4
9
8
10
11
WARNING
To avoid instability of the machine, the extend/retract
cylinder MUST BE fully retracted prior to retracting the
lift cylinders. If circumstances prevent retraction of the
extend/retract cylinder first, lower the lift cylinders the
minimum amount necessary and resume retraction of
the extend/retract cylinder as soon as possible in
accordance with the machines load chart.
WARNING
Properly support the boom before attempting to
proceed with the emergency boom lowering
procedure.
WARNING
If possible, safely remove and/or secure the load on
the machine before starting the boom lowering
procedure. If load cannot be removed, the machine
load chart MUST be followed.
NOTICE
EQUIPMENT DAMAGE. Auxiliary Hydraulic Power
Supply hydraulic oil must be compatible with hydraulic
oil shown in Section 2.4, “Fluids and Lubricant
Capacities.”