Automated line aids coffee creamer bulk bag filling, reduces waste

To lessen aeration and improve accuracy, Anchor Products (Reporoa, New Zealand) recently installed an automated packing line for filling bulk bags with sodium caseinate.

By Jim Montague, news editor November 1, 2001
A flexible screw conveyor, at top, transports sodium caseinate powder through transition the discharge adapter to Flexicon’s automated bulk bag filler. The bulk bag fills to the preset weight according to gain-in-weight information transmitted to the controller, at right, from four load cells under the filler frame. An inflatable connector and connection to the plant dust collection system eliminate dust. In front of the bag stand an automated label printer and heat sealer. The bag automatically moves on the conveyor out of the room to a stacking gantry.

T o lessen aeration and improve accuracy, Anchor Products (Reporoa, New Zealand) recently installed an automated packing line for filling bulk bags with sodium caseinate. The new line reportedly eliminates aeration experienced by rotary sack fillers, cuts dust and packaging waste by 90%, and achieves bag weight accuracy of

The powder is automatically transferred and filled by a system that includes two flexible screw conveyors, a 390-gallon capacity surge hopper, and a bulk bag filler. The 1,500-lb bags are automatically conveyed from the filler to a heat sealer and then to bulk storage. The PLC-controlled system is also tied to the plant’s PLC.

The new line was designed, built and commissioned over two months by Flexicon Corp.’s (Phillipsburg, N.J.) licensee Fresco Systems Ltd. (Auckland, New Zealand) and New Zealand’s B.W. Murdoch engineers. Anchor selected flexible screw conveyors as the most effective method for moving the difficult-to-convey powder in a restricted 33 x 23-ft space.

Overcoming aeration

Flexible screw conveyors gave Anchor and its engineers a method for overcoming the semi-free flowing powder’s tendency to aerate. (Bulk density is defined as 26 lb/ft3 at a 45°-60° angle of repose.) The flexible screw conveyors lie at a 20° angle, which combats aeration by imparting less energy into the powder than would occur at a higher angle. The screw itself is a wide, flat spiral, which presents a wider carrying surface than the typical round-wire screw. The flat screw applies a positive forward force, while reducing the radial force against the outer tube’s walls.

Anchor rejected a pneumatic conveying method, which required using a deaeration station. ‘A separator would reduce packing time and increase fines losses,’ says Keith Mason, Anchor’s former site services manager, who oversaw the installation.

The flexible screw conveyors transport the material through a 6.625-in. diameter polyethylene outer tube, which encloses the rugged, flexible stainless steel screw, driven by a low-power electric motor. As the flexible screw rotates in the tube, it self-centers, providing clearance between the screw and the tube wall, and creating a gentle rolling action that prevents degrading of the powder, which would occur in a separator.

‘Because we pack large quantities, we couldn’t allow any air to mix with the powder,’ says Mr. Mason. The bulk bag filler’s PLC-controlled vibratory densification/deaeration bed removes air, and stabilizes and settles the material.

Basic system functions

The sodium caseinate powder enters the packing room from the blending area after being spray dried and milled to the correct particle size, and then transferred to a packing bin in a weighed batch depending on the order requirement. At the control panel outside the packing room, the operator directs the powder either to the four-station rotary packing machine to fill 44- or 55-lb multi-walled sacks or to the Flexicon bulk bag filler.

The first 25-ft long flexible screw conveyor transports powder from the packing bin at a 20° angle to a height of 4 ft. The powder falls through a transition discharge adapter and metal detector to the surge hopper, which extends through the floor to the lower level. The PLC turns the flexible conveyor on and off to maintain a set level of material in the hopper.

The second 10-ft long flexible screw conveyor, supported from the surge hopper, carries the powder at a 20° angle to the automated bulk bag filler. The operator selects the filling sequence, and the bulk bag automatically fills to the preset weight. The bulk bag filler frame is mounted on four load cells that transmit gain-in-weight information to the PLC proportional to the load of the bag and filler. The PLC slows the flexible screw conveyor’s variable-speed-driven motor to dribble feed rate immediately prior to stopping the conveyor once the target weight is reached, achieving accuracy of

The flexible conveyors transfer the powder intermittently: five minutes on, one minute off. Packing rate is 7 tons/hour.

An inflatable connector seals the bag spout to eliminate dust. The fill head’s dust collection port connects to the plant dust collection system. ‘Previously we were recovering upwards of 0.05% dust per day while packing 20-kg bags. This has dropped to 0.005%,’ adds Mr. Mason.

Automatically conveying filled bags

Next, pneumatically actuated bag strap hooks automatically release the filled bag. The PLC instructs the printer to print labels for insertion in each bag. Labels contain date, product, weight and other data for traceability and stock control.

Finally, a flat-belt conveyor transfers the filled bulk bag from the filler, while a second conveyor positions the bag under a heat sealer, which seals the bulk bag liner to ensure quality of product delivered to the customer. The bag continues out of the room on the conveyor to the stacking gantry, where the bag is weighed, placed on a pallet and moved into bulk storage for stacking.

To meet New Zealand Dairy Board Standard NZCP6, the packing line equipment is constructed of food grade materials, including UHMW polyethylene for the conveyors and type 304 stainless steel with interior welds ground and polished to a sanitary finish.

Expanding markets

Because other customers have expressed interest in receiving Anchor’s sodium/calcium caseinate and total milk protein products by bulk bag, ‘We’ve had to allow for packing these products on the same line,’ says Mr. Mason. The bulk bag filler accommodates variable bag sizes between 770 to 2,000 lb. A linear actuator raises and lowers the filling head for various bag sizes.

Jim Montague, news editor