55M3500MNE rev. E
Telescopic cranes with derrick pressure sensors Calibration Manual i3500
41
Note: This procedure should not normally be necessary and should not be used before
exhausting other, more likely causes of load reading errors such as dimensional errors
(section 2.2.4) or proper no load calibration using an adequate number of calibration
points (section 2.2.6).
Some inaccuracy of load indication with very small loads at high boom angles and short
boom lengths is likely due to the small boom lift cylinder pressures encountered in this
zone. Do not use the weight of the hook block alone to judge load indication
performance, these calibrations should be done with loads in excess of 50% SWL.
If a load correction calibration is found to be necessary the minimum number of
correction factor points that must be calibrated is 2, the maximum that can be calibrated
is 20. The following notes are intended to give general guidance only as each individual
installation will be different. The full working envelope of the configuration can be
divided into different zones for load correction calibration, see diagram 2.2.13 for
examples.
Case 1
This shows a basic, two point calibration. These two points cannot have a common
angle or boom length. A load correction factor will be applied to all boom positions
whose angle and length are greater than point 1 and also whose angle and length are
smaller than point 2. A load correction factor will not be applied to boom positions
outside of this zone.
Case 2
This shows the influence of adding one additional calibration point to case 1, the pair of
numbers in each sub-zone show the calibration points used to determine the load
correction factor calculated for various points in that sub-zone.
Case 3
This shows a typical set of calibration points that will go on to use the most logical
adjacent points for interpolation purposes and also cover the full working range of the
machine.
Case 4
This shows a more practical set of calibration points that will improve the most likely
area for load errors.
Case 5 and 6
These show the results of excluding one or more of the calibration points chosen in
case 4.
To add a load correction calibration point, ensure the current duty selection matches the
actual crane configuration.
Only one load correction factor is stored at each angle/length location and the test load
used to set this factor should be greater than 50% of the Safe Working Load at each
location. Calibrating a load correction factor with smaller test loads could result in
unacceptable errors at 100% SWL.
