1 2 3 4 5 6 7 8 9 10
Concentrated Load Capacity (CLC)
How much CLC do I need? The answer to this question depends somewhat on your location and the maximum legal weight limits defined by your government and/or transportation authority. For example, in the United States, most state transportation regulations limit dual tandem axles to a maximum of 34,000 lb (15,422 kg). In most cases, you need a CLC that is designed to meet or exceed that value. However, rarely will you encounter a scale option that does not provide an adequate CLC for your area. For a company to offer a scale that doesn’t meet local ratings just doesn’t make much sense. Safety factor A truck scale with a 30-ton CLC rating offers more than 150% of the actual CLC loading the scale will encounter, providing the necessary safety factor for legal roadway weights.
CLC is a specification required by NIST/NTEP, outlined in Handbook 44, applicable to the United States and other regions that recognize these requirements. Weight limits for road-going vehicles are often expressed as the maximum weight allowed for a dual tandem axle (two axles positioned next to each other in a fixed area of about 2.5 by 1.2 meters, or 8 by 4 feet). CLC is the intended maximum dual tandem axle weight that the scale will support as designated by the scale manufacturer. How is CLC determined? The scale manufacturer declares the intended CLC value for a scale model. That value then is verified with a simple test using flat weights representing the intended maximum value. These weights are placed at various locations on the scale when it is new. Typically, the scale is then used for a short period of time (30 to 45 days), during which it is required to perform a minimum of about 300 registered weighments. The scale is then tested again to see if the original test results are repeatable in terms of weighing accuracy. If so, the Weights and Mea- sures organization grants that CLC value to the scale model. That testing does not measure physical stresses or fatigue on the scale structure as it is only checked twice in the first few months of the installation.
Common axle group weigh limit (USA) 150% of limit (recommended CLC)
~20 tons
30 tons (60,000 lb)
Let’s say you are evaluating two truck scales – one has a CLC rating of 80,000 lb (36,287 kg) and the other has a CLC rating of 100,000 lb (45,359 kg). Both offer more than twice the CLC rating needed to weigh the typical maximum legal dual tandem axle weight for over-the-road trucks in the United States. So is the scale with the higher CLC rating better than the other? No. CLC by itself is a poor means of comparison because it doesn’t reflect the scale’s quality or performance over time.
Note : In recent years, some scale manufacturers have begun having their scales certified for very large CLC weights so they can use this figure in sales discussions. In reality, many sites have used older truck scales rated at 60,000 or even 45,000 lb CLC for 20 years or more without weighbridge issues. This, combined with the limited nature of the CLC test, makes it easy to see that a higher CLC does not translate to longer scale life.
The CLC rating is frequently misunderstood. It is often cited by salespeople as a sign of the scale’s strength. While the CLC test is useful in some ways, it is not a true measure of the “strength” of the scale. Most scale buyers want a “strong” scale because they want the scale to last as long as possible, even with constant use. Unfortunately, this CLC test does not predict a scale’s resistance to fatigue, or performance over time. The truth is, even a poorly manufactured scale could pass with a high CLC rating.
50
51
Made with FlippingBook Annual report