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A commercial scale is any device that weighs commodities that are sold by increments of weight. In the food processing industry, the most common devices of this type are bagging scales. They are used to weigh sugar, many types of grain, and rice.
Since bags of these products are sold according to various increments of weight, a commercial scale performs one of the most vital functions in a food processing plant. Without it, the plant has no way of evenly filling bags. Too little product can result in overcharging customers, while too much will result in depleted inventories and diminished products. By utilizing a tool that will evenly fill each bag with a specific amount of product, plants can also eliminate the need for manual filling on the part of employees. This reduces the risk of injury that can easily result from heavy lifting, and it reduces liability as a result.
The size of a commercial scale is determined by a combination of multiple factors.
• Product density
• They way the product flows
• The number of weighments per minute
• Accuracy required for weighments
• Products weighed in the bag (gross weighments)
• Pre-weighed product that is placed in a bag (net weighments)
The wide range of possible combinations accounts for the large number of model types that are found in food processing plants all over the world. A gross weighment commercial scale will weigh the product after it has been placed in the bag. The product and the bag are collectively totaled for a combined, gross weight. A net weighment weighs the product first, before placing it into the bag. In both cases, the operator inputs the desired weight into a control system which measures out the product in increments of that amount. The choice between gross or net weighment depends largely on the stipulations of trade that exist between the plant and its buyers. Many food companies print the total net weight on the container to indicate to the consumer how much actual product they are purchasing.
A food processing plant will have to take into consideration how quickly product can be weighed and put in bags. A plant with lower daily production quotas may want to invest in simplex machines that can process 12-14 weighments per minute. Mid-level quotas may require more speed without compromising accuracy. For these operations, duplex devices that can handle 18-22 weighments per minute may be a better investment. High-volume production outfits may require triplex machines that can process weighments at a rate of 2.5 times the speed of a simplex machine.
A commercial scale may be fed by gravity or by an auger. Products that flow more or less evenly on their own can easily be processed with gravity fed machines. However, some products, such as casein and soya flour, tend to fluidize when run through a gravity fed machine. Auger feeds keep these products flowing uniformly so they can be accurately weighed. Other systems fed by gravity include gravity bulk or gravity vibratory systems. A bulk system lets the product fall directly onto the scale as a single mass, while a vibratory system sifts the product onto the scale. Typically, vibratory systems are used when weighment accuracy is a major concern.
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