FEATURE MIXING, WEIGHING & CONVEYING CONVEYOR/DISCHARGER PROVES TO BE A GEM


The abrasive qualities of garnet make it ideal for cutting metal, but difficult to move around the plant. Flexicon’s solution has shown it is up to the job


O


ne large manufacturer of machinery has been cutting its carbon steel,


stainless steel and polycarbonate sheet on a waterjet since 2001. Thirty-two kg bags of garnet were delivered on pallets, requiring operators to manually lift and dump six to seven bags into a charging hopper at the start of every 8-hour shift. Manual dumping incurred about 45 minutes of downtime, resulted in occasional spillage and generated dust, while exposing workers to potential injury. In addition, the waterjet consumed about


27 kg of garnet/h, often depleting the volume of garnet in the pressure pot prior to the end of the shift, requiring a shutdown to refill it before resuming operation. A few years later, management upgraded


the process by feeding garnet directly from 1814 kg bulk bags to the pressure pot by installing an automated bulk bag discharging-conveying system from Flexicon. Called a JET-FEED garnet delivery


system, it consists of a BULK-OUT bulk bag discharger, specifically a BFF model with a removable bag lifting frame that is positioned by forklift above a bulk bag. An operator can then connect bag straps to the frame, which is


forklifted into cradles of spring-loaded POP-TOP bag extension posts. The spout is connected by pulling it


through an iris valve, closing the valve around the spout, untying the drawstring, and closing the hopper intake chute. Opening the iris valve slowly prevents uncontrolled bursts of garnet from the bag and dusting from displaced air, while eliminating the spillage that previously occurred during manual bag slitting and dumping. When full, the heavyweight bag


compresses the spring-loaded bag extension posts, which begin to stretch upward as the bag lightens, elongating the bag to promote complete discharge through the spout. Additional flow promotion is provided by FLOW FLEXER bag activators that raise and lower opposite bottom edges of the bag with increasingly longer strokes as the bag lightens, raising the bag bottom into a steep 'V" shape free of dead spots. The fully-enclosed high-flow hopper is


designed with a steep back wall and skewed sidewalls that form a trapezoidal area which reduces the ability of garnet to establish a bridge between the hopper sidewalls. Instead, garnet topples and flows toward and down the steep


CHECK & DETECT IN SEPARATE SECTIONS


As a result of a clever innovation by LOMA SYSTEMS, food manufacturers are able to provide retailers with assurances that their packaged products contain at least the quantity displayed on the label, and not less. Intended to be used to complement end-of-line checkweighing, the X-weigh feature is available on LOMA’s X5 X-ray system, is fast to set-up and uses algorithms to convert data from an image into a weight. Food manufacturers, by law in the UK, should package their products to an average measurement that is


on the label, ensuring that a random sample is packed according to the ‘three packers’ rule, whereby the contents of the packages must not be less, on average, than the weight on the label, only a small number can fall below a certain margin of error, known as the ‘tolerable negative error’ (TNE) and that no package can be underweight by more than twice the TNE. Weight discrepancies in packaged goods can occur when products contain multiple sections - such as


yogurts or ready meals. Whereas a checkweigher will only check the total weight, X-weigh will check all compartments separately providing both an overall and an individual weight for each. If there is too little of one component, potentially caused by an issue with a portioning machine, X-weigh will alert accordingly. The X-weigh feature is also unaffected by vibrations, belt speed and other factors that are known to degrade traditional checkweigher performance. For the best weighing results when using the feature, the inspected product needs to be


LOMA Systems 18


uniform/homogenous and consistent from pack to pack. To achieve optimum results with an inhomogeneous product, several samples of the product are needed to set the weight range. Loma recommends pairing the X5 X-ray with a CW3 Checkweigher to create a Combination System. https://www.loma.com/en/about-us/news-press-releases/x-weigh-feature-150720


OCTOBER 2020 | PROCESS & CONTROL


By converting from manual dumping to automated discharging from bulk bags, the plant improved worker safety, plant cleanliness and uptime, while reducing the ongoing expense of a costly consumable


back wall, eliminating the need for pneumatic or mechanical hopper agitation devices. The qualities that enable garnet to


abrade through hardened steel also make it difficult to move without damaging the conveyor. The solution came in the form of a


Flexicon flexible screw conveyor, whose only moving part contacting material is a rugged inner screw. "Loose-footed," the stainless steel screw is driven from its upper end beyond the point at which garnet exits through a discharge spout, preventing material contact with seals and associated maintenance, wear and downtime. As the screw rotates, it self-centres


The qualities that enable garnet to abrade through hardened steel also make it difficult to move without damaging the conveyor. Fortunately, Flexicon’s flexible screw conveyor offers features that prevent the garnet from grinding between the screw and the tube wall


within the abrasion-resistant polymer tube, preventing garnet from grinding between the screw and tube wall, maximising the life of material contact components. The conveyor elevates garnet at a 45˚


incline before curving to horizontal for a total run of approximately 12m. The enclosed system maintains the same


humidity levels as within the bulk bag, preventing garnet particles from agglomerating and resisting flow when too moist, or developing static charges when too dry. Garnet exiting the conveyor gravity


discharges through flexible downspouting into the waterjet's pressure pot. The conveyor can be started and stopped manually, or automatically by a PLC linked to high and low level sensors installed on the pressure pot. In the closed loop system, spent water


and garnet collected in the catcher table is pumped to a centrifuge that extracts solids, depositing it in a bulk bag-lined hopper for recycling. The garnet is returned to the supplier, which cleans and screens it to reclaim the portion of spent garnet that is suitable for re-use. By converting from manual dumping to


automated discharging from bulk bags, the plant improved worker safety, plant cleanliness and uptime, while reducing the ongoing expense of a costly consumable.


Flexicon (Europe) www.flexicon.co.uk


/ PROCESS&CONTROL


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