Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/772143
AGGREGATES MANAGER / January 2017 33 T ruck scales are a vital tool for aggregate operations, and the performance of the scale can have an enormous impact on profi tabili- ty. The truck scale is often the "cash register" of an operation through which materials are bought and sold and where profi t and loss is measured. A challenge facing many truck scale owners today is determining how to maximize the life of that cash register with the routine wear and tear of aggregate opera- tions. Today, the average cost of a truck scale service call can run anywhere from a few hundred dollars to several thousand dollars depending on the age, condition, type of problem, and design of the equipment being used. Chances are, if maintenance costs are already signifi cant, they will increase in the future. Heavily concentrated loads and high-traf- fi c volumes make rock and gravel applications some of the most demanding in the weighing industry. With that in mind, a well-designed truck scale and proper maintenance plan are the two most important elements in ensuring the sustained profi tability of your aggregate facility. Maintenance frequency is directly related to the daily truck volume and axle loads of the vehicle being weighed. A thorough in- spection is recommended, at a minimum, ev- ery six months. However, number of weigh- ments, climate, and the value of the product being weighed could change that frequency. Aside from the actual calibration, most of the inspection will consist of you or your scale technician conducting a visual inspection of the scale, foundation, and surrounding area. Weighbridge Proper weighbridge inspection is essential to ensure accuracy and consistent perfor- mance of a truck scale. Visual inspection of the top-deck surface, including welds, should be performed on each maintenance visit. Areas beneath the bridge should be inspected for potential mechanical bindings as a result of debris accumulation, loose bolts, and misalignment of the suspension system. Debris or ice buildup between the approach bulkhead and the end of the scale, as well as between the scale modules, should also be checked and removed. Paint coating condi- tions on the scale should be examined and noted yearly. Depending on weighbridge design, geographical location, load materi- al, and environmental factors, removing the weighbridge from the foundation for sand- blasting and paint may be required. Excessive corrosion could indicate complete replacement of the weighbridge. Foundation A truck scale is only as good as the founda- tion on which it rests. Keeping the foundation clean and well drained will provide more accurate and dependable vehicle weighing. A quick visual check of sump pumps and drains should be done at least once a month. The condition of the concrete piers or slab and concrete approaches are very important for maximum equipment performance. Approach- es to and from the scale should be level to ensure a smooth transition from the approach to the scale. The steel coping or trim on the approach head walls and/or pit walls should be checked for proper anchoring or wear. Areas around the load cells should be inspected for binding due to debris build-up. A minimum clearance of 0.75 inches should be provided between the weighbridge and the headwall and side walls when applicable. Any cracks in the concrete or evidence of heaving due to frost or poor soil conditions should be recorded and resolved immediately. Foundation issues are common causes for inaccurate scale performance. Load cells Examine load cells and the area surrounding them. The load cell area may contain dirt and debris that has built up since the scale's last check. Load cells must have clearance to de- fl ect through their capacity range. The same debris that can bind the scale deck can also keep the load cells and suspension compo- nents from moving freely. Inspect load cell cables for damage. If dam- age is present, the seal is probably degraded as well. To combat this problem, some man- ufacturers offer rigid or fl exible metal conduit to run the cable through, providing a layer of protection that's nearly impervious to damage from rodents. Even though steel over braid cable provides more protection from damage than cable sheathed with polyurethane or plastic, they still need to be checked as well. When exposed to moisture, cables can become