Rice Lake BCi Belt Scale - Maintenance & Troubleshooting Manual - Manual (Page 9)

Belt Scale Maintenance Instructions - Scale Calibration Maintenance 5
3.0 Scale Calibration Maintenance
It is generally advised, throughout the belt scale industry, that calibration checks be made frequently during the
weeks after initial installation, then to increase the time frame between calibrations as statistical results are
obtained. Calibrating too often can cost production time. Defining a calibration schedule is a balance of
maintaining the accuracy required and minimizing the cost associated with calibrating the scale.
There are several considerations when determining the proper calibration interval for a conveyor belt scale such
as:
• The condition of the conveyor
• The expected accuracy
• Seasonal temperature changes
• Conveyor maintenance
The condition of the conveyor and the accuracy required should be used to set the calibration interval, but wide
temperature swings and conveyor maintenance are events that should be considered to determine when you may
need additional calibration.
3.1 Where do you Start?
The condition of the conveyor is the primary consideration when determining the belt scale calibration interval,
considering the calibration for the current model belt scales (that are properly installed), is mainly to adjust for
changes in the conveyor. Starting with a fairly short interval is a good ideas since it is impossible to quantify the
condition of the conveyor or predict how much error there will be based on a specific conveyor problem. It is
suggested to start once every week or two in the beginning of an installation.
During the belt scale calibration, most integrators will provide a deviation (the error between the previous
calibration and the current calibration); this number is the most useful tool in determining the proper calibration
period for that scale. If, after several calibration intervals, you find that the deviations are less than the accuracy
you want to maintain, the calibration interval can be increased. If the deviations are higher than the desired
accuracy, you should be calibrating more frequently.
3.2 Weather Issues
Wide temperature changes can cause a let to be longer or shorter. Of course, changes in length will affect the
tension of the belt as well as alter the accuracy. Using a gravity tensioning device on conveyors longer than 100
feet and setting the belt tension as loose as possible, without allowing the belt to slip, will minimize the effects of
temperature changes. Even when taking these precautions, it is still a good idea to include at least two
calibrations per session.
3.3 Conveyor Maintenance
There are many things that can occur on the conveyor and affect the scale’s accuracy causing a shift in the zero
calibration such as:
• adjusting the tracking or gravity take up
• replacing or even lubricating the idler
• changing the belt speed
it’s a good idea to always calibrate the scale after any maintenance is done to the conveyor. Set up a system to
flag conveyor maintenance when regular maintenance is being performed.