16.4.4 Other functional characteristics
Crane block by the attainment of the mechanical stroke end of the lifting
ram.
The limiting device may intervene also during loadless crane operation fol-
lowing a pressure peak provoked by the attainment of the stroke end of the
lifting ram at high speed. In this condition, the permitted manoeuvres can be
activated, but to reset the block it is necessary to perform the opposite manoe-
uvre to the one that caused the block. Then the limiting device checks if the
pressure goes down and therefore decides whether to remove the block, or to
maintain it. Such type of reset works only one time.
Activation of the temporised exclusion device of the lifting moment limi-
ting device
Such device has been added in order to solve the problem of the lifting of
heavy and bulky loads with the extension boom sections almost completely re-
entered. Once above the horizontal line (with pressure reaching the activation
level of the lifting moment limiting device), during the load descent, due to the
dynamic overload caused by the descent, the lifting moment limiting device
is activated and therefore it becomes impossible to put down the load on the
ground.
The temporised exclusion device sets remedy to what described above as fol-
lows:
With the crane in block condition, maintain the command for the extensions
boom re-entry until stroke end until "LMI" is displayed at the top right corner
of the radio remote and contemporarily the icon (flag) is displayed at the right
end corner.
Release the lever commanding the extensions booms and then press the
exclusion device button of the lifting moment limiting device (if the procedure
has been correctly executed, "ELMI" will be displayed at the top right corner
of the radio remote controller). From this moment on you have at your disposal
five (5) seconds to carry out the descent of the outer boom in order to bring
the load under the horizontal line and therefore put it down on the ground. As
soon as the crane exits the block, "ELMI" is no more displayed.
After the execution of such manoeuvre (5 seconds) wait at least one (1) minu-
te in order to be allowed to carry out the manoeuvre once again.
(!) ATTENTION (!)
Activation of the exclusion device of the lifting moment limiting device.
Only the outer boom descent is allowed.
When the operator uses this device, it means that he wishes to override
the lifting moment lifting device in order to make some manoeuvres (which
would be impossible with the device active) that bring the moment to within
the maximum level, but involve an overload condition.
In such an emergency condition (where the lifting moment limiting devi-
ce has been disabled), the operator, who is the main responsible for the
machine safety, must:
- carefully consider the manoeuvres required to return to normal
working conditions: it is however compulsory to effect the re-entry
of the extension booms at first;
- calmly and carefully assess the type and scale of the hazards arising
from these manoeuvres and the possible reaction of the crane (tipping
over, frame overload, uncontrolled fall of the load due to a hydraulic
system overload etc.);
- make all movements as slowly as possible to reduce the dynamic
over load to the minimum.
16.4.4
CONTROLS TO OPERATE
THE CRANE
GR4_5 - EVOLUTION
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