User's Manual

GM550 v1043 FCC-IC.doc Revision 2 71
Load cell maintenance
WARNING! Heavy shock may affect load indication accuracy. Inspect the load cell
regularly for clearly visible dents or scratches. Test the load indication if collision
damage is visible.
Reading Accuracy
LSI Load cells are pre-calibrated at the factory. No “zeroing” or other calibration is required on
installation. Each link is heat treated to age the steel and ensure stable readings for many years;
load cells are individually temperature compensated to guarantee accuracy.
Load cells are calibrated to indicate between 100% and 104% of their Safe Working Load (SWL).
SAE J-159 4.2.1 recommends load indicating devices should show not less than 100% of the
actual load and not more than 110% of the actual load.
Recommended Maintenance
Load Testing
LSI recommends testing the load cell every year for accuracy. The simplest way of testing a
load cell is to lift at least two known weights. A test weight should be known with an accuracy
of ±1%. If the load cell is installed at the boom tip dead end, all additional equipment such as
blocks, slings, sensors, etc. should also be known to an accuracy of ±1%.
Determine the accuracy of the tested system with the following formula:
(Reference: SAE-J-159 7.3)
The test loads must be significant relative to the load cell capacity. The minimum test weight
is about 20% of the safe working load; a good test weight is greater than 50% of the SWL.
For example, a 30,000 Lbs load cell on 4 parts of line has a SWL of 120,000 Lbs; the
minimum test load in this case would be 24,000 lbs, a good test load would be 60,000 lbs or
more.
Taking Care of the Load Cell
• Battery: Lithium batteries over than 18 months old (alkaline batteries over 6 months old)
should be changed at the first available planned inspection even if there is not yet a low
battery warning. This will avoid costly delays in the field. See section 3 of this manual for
details.
• Inside the load cell transmitter: verify that no corrosion is visible on the battery holder. If
some trace of corrosion is visible, gentle rub it and put a small amount of dielectric
grease* on each battery holder post to protect the contact.
• Mechanical stresses: verify the load cell sides for dents or heavy scratches. The side of
the load cell under the transmitter box is the most sensitive region. Engraving a number in
this area will affect load cell accuracy and reliability. If the transmitter box has been hit and
the box does not fit perfectly to the underlying link, please call LSI to have it repaired.
Engraving on the transmitter box sides will not affect reading.
*
Dow Corning dielectric grease #4