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www.rockproducts.com ROCK products • May 2015 • 87 EQUIPMENT & TECHNOLOGY MAINTENANCE & WEAR PARTS A ggregates operations purchase scales because the value of goods entering or exiting a plant is based on their weight. Without assured scale accuracy a company can lose thou- sands, if not hundreds of thousands of dollars annually. Depending on the requirements and type of weighing device, annual main- tenance costs for a truck scale run any- where from $1,000 to $3,000. If one compares that to the potential cost of weighing errors, most users find that a good scale maintenance program more than pays for itself; oftentimes it also pays for the actual cost of the scale. To be most effective, a scale-main- tenance program must have five key components: • Use of a state-licensed service pro- vider. • Conducting calibration using state- certified test weights with written calibration and test report for proof of accuracy. • A thorough testing process. • Visual inspection services and minor repairs. • Thorough reporting. Calibration is the key component of periodic maintenance. After a scale is installed, it is tested by the governing state's weights and measures organiza- tion. This test ensures the scale's com- mercial accuracy and protects the scale buyer, scale seller and scale installation company. Upon state approval, the scale is certified and open for weighing. However, it is important to under- stand that this initial calibration does not come with a guarantee for contin- ued accuracy. Calibration can never be guaranteed, because accuracy is highly dependent on the way a scale is used and cared for. Weather, use and wear are just a few of the factors that can change the accuracy of a weighing device. That is why periodic calibration is so essential. Test frequency depends on a variety of factors, including: • Number of weighments per day. • Price of the product being weighed. • Number of days the scale is used annually. • Acceptable error rate. What's the potential loss from a poor- ly calibrated scale? Seemingly minimal errors can substantially cut into profits over time. Take the Acme Aggregate Co., example shown below, in which 200 lb. may appear miniscule, since a typical truckload of sand or gravel can exceed 80,000 lb. However, when one does the math, the truth is revealed – an annual revenue variance of about $345,000. Acme Aggregate Co. Weighing volume: 500 trucks per day. Weighing frequency: Five days per week. Product value: $26.50 per ton. Scale inaccuracy: -200 lb. Lost annual revenue: $344,500. Use A State-Licensed Service Provider It is important to understand that the state weights and measures organiza- tion is the only entity that can issue a scale certification. A commercial scale company cannot certify a scale – but it does have the authority to recalibrate and reinstate an inaccurate scale that has been "tagged-out" by the state, as long as the scale company is state-li- censed and registered in good stand- ing. (Tagged-out means the scale has failed a state weights and measures accuracy test, so the state has attached a lockout tag to the scale, rendering it unusable for commercial trade.) So make sure the commercial scale company you are using shows you their valid license. Conduct Calibration Using State-Certified Test Weights Calibration must be completed using state-certified test weights. An estab- lished scale service company typically has its entire inventory of test weights tested and certified annually, in accor- dance with state weights and measures standards. Beware of service companies that test only a portion of their overall weight inventory each year. Preparing the weights and delivering them to a metrology laboratory for test- ing requires an enormous amount of time and money, so it may be tempting Five Key Components of a Good Scale Maintenance Program By Russ Desilets