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Bulk Bag Discharger Cuts Production Time for Fish Food Manufacturer

April 23, 2008
A Type 5 Spiroflow bulk bag discharger unloading a bag into a top frame

With the installation of a Type 5 Spiroflow bulk bag discharger, Skretting of Longridge, a leading fish food manufacturer in the UK, has cut its production time from 25 to 30 minutes to five minutes in discharging each of the 11 ingredients used in the production of fish food for its industrial fish-farming operation. The Type 5 discharger is being used instead of simply hanging the bags from a forklift truck.

Skretting is the largest aquaculture feeds producer in the UK and leads the market with innovative feeds and feeding expertise. Located in Lancashire, it is part of the Nutreco group of companies, which has operations in 22 countries, including the United States, and employs more than 12,000 people. Global turnover for the company is 3.8 million Euros, or roughly 5.4 million U.S. dollars. At its Longridge site, Skretting produces a variety of food for industrial trout farming as well as some for salmon. The company’s 30 employees produce 24,000 tons of fish food annually, or about 100 tons day.

The bulk bag discharger supplied to Skretting is specifically designed for applications with restricted headroom. At Skretting there is a mezzanine floor area directly above the location of the discharger, which would make it almost impossible to lift full bags into a standard discharger safely. “There is no comparison to the previous way we operated,” said Bill Edmondson, production manager at Skretting. “Our Spiroflow discharger has enabled us to increase productivity while using the forklift truck for other duties while the bulk bags are being emptied.”

A forklift truck lifting a bag onto the upper section of the frame where it is safely locked into place

The material-handling system at Skretting was installed more than eight years ago by a specialist contractor who included a “simple” bulk bag–unloading arrangement that fed ingredients into a Spiroflow aeromechanical conveyor. The conveyor lifts the products up to a horizontal-screw conveyor onto the floor above. The screw conveyor has 11 outlets, each of which delivers ingredients to its appropriate storage bunkers. From there, weighed measures of the required ingredients are loaded into a mixer and, finally, the mixture is pelleted, packed, and ready for dispatch.

A bag safely locked into place at Skretting of Longridge, the largest feeds producer in the UK

It was the so-called simple bulk bag–unloading arrangement that proved to be the bottleneck in the production process and the cause of constant frustration to the operators. Consisting of just a lidded hopper with a spigot to which the neck of the bulk bag was attached, the “simple” bulk bag–unloading arrangement required the presence of a forklift truck for the duration of discharge since there was no other means to support the bag. In addition, an operator had to be on standby to help with poor-flowing or compacted products.

The Type 5 bulk bag discharger was integrated into the existing aeromechanical conveyor and horizontal-screw conveyor setup. The discharger has two sections. The upper section, which holds the bags, is lifted off at its base and lowered to ground level. Here, by way of a lifting frame, full bags can be loaded by a forklift truck, whose forks only have to be raised a little higher than the height of the bag and its extended lifting loops. Once the bag is safely in place, the top section is lifted via the fork channels at its base back onto the lower section of the discharger and locked into place. There is a dust-tight docking seal between the upper and lower sections. An access door in the discharger hopper allows the bag to be untied without emissions or spillage. Once the bag is untied, flow begins and this door is closed.

Pneumatically operated bag-base massagers have been fitted to the lower half of the discharger at Skretting. They are there to deal with any products that are poor flowing or that have become compacted during transit. It is these base massagers that make it essential that the two sections of the discharger be locked together. The model T5 discharger incorporates the same spring-loaded side-tension arms as all other models in the range. These raise the bulk bag as it empties, helping to ensure complete discharge and prevent the neck of the bag from sagging into the conveyor below.

Spiroflow Systems Inc., Charlotte, NC, supplies standard and custom powder-handling equipment, specializing in bulk bag dischargers and fillers; mechanical, flexible, and pneumatic conveyors; and bag-packing equipment. For more information, call 704-291-9595 or visit www.spiroflowsystems.com.