When electronic weighbridges started replacing mechanical weighbridges which utilised lever systems pivoting on bearings and knife-edges, one of the primary selling points was the greatly reduced servicing requirements as the new weighbridges contained no moving parts. Many weighbridge owners took this to mean load cell based weighbridges don’t need servicing at all.
True, many of the mechanical components of a mechanical weighbridge were eliminated, but even though the load cells are deemed to be fully electronic, basic mechanical principles still apply. Weighbridge load cells, pendle pins and mounting cups do require movement to function correctly and if there is movement then there will be wear and tear if maintenance requirements are neglected.
Most modern weighbridge load cells are based on the rocker pin design and fitted with hardened steel cups top and bottom with just enough internal clearance to allow the loadcell to freely rock back and forth to a maximum of approximately 5-8 degrees. This rocking clearance is necessary to allow for expansion and contraction of the weighbridge deck caused by temperature changes and for inherent weighbridge movements caused by trucks braking and accelerating on the weighbridge
The degree of load cell tilt must be controlled as the load cells can suffer physical deformation if allowed to tilt at higher than expected angles. The load cell tilt is regulated by the total weighbridge movement, which is only limited by adjustable physical stops usually fitted to the ends of the weighbridge.
These end stops need regular adjustment due to seasonal temperature variations that can significantly affect end stop clearances. Weighbridges expand in length during the hotter months and the end stop clearances are increased to prevent the weighbridge from binding hard against the stops and causing weighing errors. However, during the cooler months, as the weighbridge shrinks the end stops need adjusting to prevent excessive weighbridge end movements. If these end stops are not adjusted correctly, the usual result is a dramatic shortening of load cell life expectancy.
Excessively heavy braking and acceleration of trucks can damage the end stop hardware resulting in increased weighbridge end clearances. Speed humps fitted to the weighbridge approaches can significantly reduce truck speeds and resulting load cell damage.
The hardened steel cups and the load cell pendles need to be inspected regularly for damage caused by excessive loadings and excessive weighbridge movement. The entry of dust and dirt into the cups can form a grinding paste when mixed with the grease and quickly render both the cups and load cell in-operatable.
Accuweigh is Australia’s largest industrial weighing company and has branches with weighbridge crews and test trucks stationed in all mainland states providing regular service and maintenance to all brands and types of weighbridges.