Grove Published 3-25-2020, Control # 643-04 3-73
GRT880 OPERATOR MANUAL OPERATING CONTROLS AND PROCEDURES
the load. Weight of any other load handling devices such as
chains, slings, or spreader bars must also be added to the
weight of the load.
NOTE: Information in the following paragraph is an
example only of how to compute a lift. Numbers
may not match load chart in the crane cab.
Example: A concrete beam weighing 2268 kg (5000 lb)
needs to be lifted to a height of 9.1 m (30 ft) at a radius of
15.2 m (50 ft) (maximum). The range diagram indicates the
boom must be extended to 18.9 m (62 ft) to reach a height of
9.1 m (30 ft) at a radius of 15.2 m (50 ft).
First check the crane for load handling devices. In our
example, the crane is equipped with a auxiliary boom nose
(rooster sheave) and a five ton overhaul ball. The rooster
sheave is 50 kg (110 lb), and the overhaul ball is 78 kg
(172 lb) for a total of 128 kg (282 lb). The lift requires slings
and spreader bars weighing 159 kg (350 lb) which makes
the total weight for the load handling devices 286 kg (632 lb).
A check of the load chart for a 15.2 m (50 ft) radius and
19.5 m (64 ft) of boom length shows a capacity of 3601 kg
(7940 lb) on outriggers over-front and 4970 lb on outriggers
360 degrees.
Subtract load handling weight of 632 lb from load capacity of
3601 kg (7940 lb) and 2254 kg (4970 lb). The result is a
weight capacity of 3315 kg (7308 lb) over-the-front and
1968 kg (4338 lb) for 360 degrees.
We are restricted in making the lift over-front only, with a
boom angle of about 29 degrees.
Proper Crane Leveling
ASME B30.5 specifies if a crane is not level within 1% of
grade, allowable capacities must be reduced. Therefore,
whether lifting on rubber or outriggers, it is essential the
crane is level to within 1% of grade. The bubble level
indicator provided on the crane is calibrated to be accurate
within 1% of grade.
To properly level the crane, the boom must be positioned
over front of the crane, fully lowered to horizontal and fully
retracted (for cranes fitted with a boom rest, boom shall be
stowed onto the rest). Raise and level crane following
instructions for Using Outriggers, page 3-73.
A working crane may settle during lifting operations.
Frequently check the crane for level. When rechecking the
crane for level, the boom must be positioned over the front of
the crane, fully lowered to horizontal and fully retracted (for
cranes fitted with a boom rest, the boom shall be stowed
onto the rest). If necessary, relevel the crane following
instructions for Using Outriggers, page 3-73.
Level Indicator Adjustment
The Level Indicator should be checked periodically; if it is
suspected that the Level Indicator is out of adjustment, verify
and adjust the level as follows:
1. Position crane on a firm, level surface.
2. Extend and set outriggers. Level crane, as indicated by
the level indicator, using the outriggers.
3. Place a miracle pointer level, carpenter level, or similar
type device on a machined surface such as the turntable
bearing or bearing mounting surfaces.
4. Using the outriggers, level crane as indicated on the
leveling device used in step 3.
5. Using level indicator mounting screws, adjust level
indicator to show level.
Crane Functions
Using Outriggers
Outriggers are operated from the front console in the cab or
using jog dial on the armrest.
DANGER
To prevent serious injury or death, keep clear of moving
outrigger beams/jacks.
DANGER
Death or serious injury could result from improper crane
setup on outriggers.
WARNING
Be sure the outriggers are properly extended and set, and
the crane is level for operation on outriggers.
All four outrigger beams must be equally extended to the
mid position vertical stripe or fully extended position
before beginning operation.
WARNING
When operating the crane on outriggers, the outriggers
should always be fully extended or locked in the mid-
extend position.
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