Flexicon Corporation (Australia)
has installed several flexible screw conveyors at the production facilities of Sanitarium Health Foods, a major manufacturer of peanut butter in Australia.
Sanitarium Health Foods blends several peanut varieties to give their brand a distinct flavour and aroma. The process involves emptying shelled and cooked peanut stock into a bin, and conveying it to a porcelain peanut mill, where it is ground and blended to the desired consistency.
The company switched from buying whole peanuts to diced and broken peanuts, which reduced costs with no impact on quality of the finished product. Plant Engineering Manager Carl Caldwell-Cook however found that the rigid-auger conveyance system, which had been transporting whole nuts efficiently, was turning the broken nut stock into peanut butter even as it was being augered to the mill.
Replacing the conveyor with a pneumatic or a gravity feed system was too complex, and would lack the necessary control to prevent frequent blockages of the mill's infeed side. Dumping peanut stock directly into the mill's inlet was also not an option, considering the quantities involved. The process required a controlled rate of feed to prevent the nuts clogging the mill inlet.
Since Flexicon had installed several flexible screw conveyors at Sanitarium’s seven production sites, it was asked to design a conveyor for the peanut butter production line.
The diced and broken peanuts are emptied from bulk bags into an 80-litre hopper from which a 3.25m long, 90mm diameter flexible screw conveyor transports the stock at a 45º incline to a height of 3.45m above the floor. The material gravity feeds through a charging adapter and downspout into the mill at a conveying rate of 2.46m³ per hour.
The peanut stock has a bulk density of 480 kg/m³, medium oil content and an angle of repose of 60º, with its non-free-flowing characteristics making it prone to packing, caking, bridging and cavitation in a conventional flexible screw conveyor and hopper.
Sanitarium employed Flexicon's Bev-Con flexible screw for conveying materials that tend to pack, cake, smear, seize or break apart. The flexible screw conveyor imparts high directional forces and minimal radial forces while significantly reducing the residence time of material in the conveyor, eliminating or minimising product degradation.
Being an enclosed conveyor system, product moisture and temperature levels are maintained during conveying, preventing contamination of the material and plant environment. Additionally, the peanut stock does not come in contact with seals or bearings since the conveyor's motor drive is coupled to the upper end of the flexible screw above the point at which material is discharged.
The Sanitarium conveying unit consists of the hopper and a flexible screw conveyor on a caster-mounted frame to roll between the mill and the cleaning area during product changeovers. The clean-out cap on the bottom end of the tube is removed and the screw rotation reversed to evacuate residual material and flush the internals. The screw can also be removed for sanitising and inspection.
All material contact surfaces of the conveyor system with the exception of the plastic outer tube are made of stainless steel with food grade finish.
The conveyor's electrical controls are mounted on the mobile frame in a stainless steel enclosure consisting of a safety relay, start, stop, jog and reverse controls, and an illuminated reset button. A capacitive-type proximity level switch mounted in a food-grade Teflon sheath inside the hopper alerts the operator about low levels of peanut stock.