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April 16, 2020
5 Min Read
Control systems automatically weigh and feed the right amount of material.
The stark reality of empty supermarket shelves has forced consumers to learn about supply chains and forced processors to question the stability of their supply chains. Without reliable access to raw material staples such as flour, sugar, and salt, many processors simply cannot produce. While many consumers remain unaware of the coming shortage of a broad range of foods, most processors pay close attention to their input costs. They understand the impact of last year's widespread flooding and wild fires, and how the destruction of huge swaths of croplands, pastures, and vineyards translates to less crops, less livestock, and more scarcity worldwide.
This global decline in agricultural production drives up the input costs for the processor and must drive up the price at the wholesale and consumer levels accordingly. Now, every ingredient has become more and more precious and the cost of waste has become less and less acceptable.
The following considerations are offered to help identify areas in the plant that are prone to product loss and to minimize its impact:
In most plants, the receiving area represents the primary source of waste as product loss. Especially true among smaller companies and those working in older facilities, receiving typically involves unloading bulk bags from delivery trucks, raising them on a lift truck, and transferring them onto storage racks. It is not uncommon for a forklift tine to puncture a bulk bag or gaylord or for a sack to slip from its pallet. The spillage from one bag on one delivery won't disrupt production or show up on the bottom line. But over time, the spillage from one bag lost on every delivery may show up as an unexpectedly high cost of raw materials.
Moving downstream, transferring ingredients from one stage to another often invites product loss. Pulling a bulk bag from storage risks contact via the forklift. Emptying the bag into a sack tipping station, hopper, screener, or mixer risks loss as spillage, dust, and incomplete bag emptying. Moving the ingredients on an exposed belt conveyor, bucket elevator, or other equipment also risks loss, as well as contamination. Training workers to take extra care when handling ingredients may be helpful and--if the volume permits--a vertical silo storage system with pneumatic conveying for material transfer may be considered. -
Connections, Seals, and Leaks
From touring hundreds of processing facilities around the world over the years, it seems many plant managers tolerate a fair amount of product loss as a cost of doing business. Producing huge quantities of finished product from huge quantities of raw materials under tight production deadlines often overshadows a one percent loss as waste. The bigger the operation, the easier it can become to ignore the little piles of powder that gradually form under a worn pipe elbow, for example, or from a leaking rotary valve. However, the larger the operation, the larger the value of the one percent loss as waste. This can add up quickly but in a time of projected material scarcity, one percent costs far too much. Tolerating more than one percent becomes simply irresponsible. Operating in a workplace littered with various powders also creates both a combustible dust hazard and a slips, trips, and falls hazard, while compromising the cleanliness required for sanitary processing.
Downtime due to an equipment failure is often a choice that can be avoided. Before investing in new equipment, pay close attention to maintaining the existing equipment. Start with piping, elbows, valves, rotary airlocks, and any connections. Leaks commonly occur first at these links. It isn't difficult to check for leaks and seal them as a minor repair before they need replacement. Rotary valves and other machinery that rely on shafts and bearings will eventually wear the seal and need repair, but better to repair the seal than replace the entire bearing assembly while under the weight of unplanned downtime.
Mixers, blenders, and other process equipment also rely on secure seals that dry out over time. Consider the discharge at the bottom of a mixer. A leak at the seal results in a loss of finished product - even worse than a loss of raw material at receiving. A complete failure at the discharge may result in the loss of an entire batch as waste and cause a sticky mess spanning two stories. Yet for most maintenance technicians, checking seals is standard practice and replacing worn seals is an easy project, if detected in time. Similar seals are used in mixers, dryers, and vessels around access doors, hatches, and ports for access to the interior and these also need to be inspected periodically to verify their condition.
Human error represents another source of product waste common to nearly every facility. As many managers struggle with finding and keeping capable staffers, it is no secret that an occasional batch needs to be discarded as waste due to operator error or a lapse of attention. Depending on the size of the batch, the time and materials required to rework the product, and the time required to clean the machinery, one wasted batch usually costs thousands of dollars in hard costs plus more in time and other less tangible costs, and these costs are far more likely to jump in the coming years than to decline. Operators given proper training and supported with ongoing reinforcement may catch errors before they happen. For an additional measure of prevention, a range of available control technology can address product loss. Digital records, for example, document ingredient usage through the feeder to track consumption and verify that only the desired amount of material is being used without excess.
Do the Math
While a product loss of 1% may be tolerated, especially when working with relatively inexpensive raw materials, a 2% loss typically triggers not only a maintenance check but an investigation into new machinery and equipment. In a scenario where nearly every ingredient becomes a high-value ingredient, identifying and addressing sources of product loss may permit an increase in on-spec product with less waste, less labor, and at reduced energy costs.
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