There are three main objectives when filling a bulk bag. First, to be able to rig the bag simply, and safely. Second, to obtain accurate and reliable weighing of the bag contents. Third, to produce a dense, stable and transportable bag.

There are eleven basic functions to look for in a filling machine. If the filling machine you select offers these features, the above objectives will be met, even with the most difficult of ingredients.

1. Secure the bag by the four corner loops
2. Attach and secure the inlet spout
3. Inflate the bag or liner
4. Exhaust the displaced air
5. Support the bottom of the bag on initial filling
6. Use bag weight to pull sides straight
7. Produce a straight, flat topped, stable bag
8. Release the inlet spout and loops, remove by fork truck
9. Provide operator interface (controls) to initiate fill sequence
10. Chest level operator access
11. Adjustable for different bag heights
    

A bulk bag typically has four loops to properly suspend it from hanger arms on the filling machine. Other styles exist (see Bulk Bags section of Sales Binder). The suspended bag will be centered under the fill head. This is important because it ensures that the ingredient will fill symmetrically and produce a straight bag. The bag bottom must be supported when filling is initiated, otherwise the bag bottom will take a sack-like shape. Thereafter, however, the bag must be allowed to hang in order to let the fabric stretch to its final shape and acquire straight sides. A suspended bag stretches during filling and produces: stable bags, straight sides, no wrinkles, and allows proper compacting.

A well designed fill head is imperative to ensure that the bulk bag is held securely open at the spout. It should not pinch or put pressure on the spout so as to tear or cut it. An ideal arrangement is an inflatable bladder device which seals the bag or liner against a fixed retaining ring. The operator should be able to visually check if the liner has been properly inflated before starting the fill.



The filling head consists of a flared outer tube, a machined plastic bag/liner fixed retaining ring and a rubber seal bonded to the filling head. During liner inflation, the rubber seals against the fixed ring and holds the FIBC or liner in place.

In order for a liner to lie snugly along the contours of the bag, it must be inflated. (Sometimes it is advisable to inflate bag as well, and inflation also allows for nitrogen purging.) This eliminates the danger of folds or twists which promote weak spots and increase the likelihood of a crooked filled bag. To properly monitor the position of the liner, the operator must be in an elevated position. The operator must be able to feel that the liner is in the correct position.

Properly inflated lined bag inflated and vented filling system results in straight sides full bottom corners will stack will keep its shape during transport will discharge fully
Bag with folded liner liner was incorrectly positioned, folds allowed to form sides have begun to mis-shape bag is not stackable will continue to alter shape during transport ingredient will get stuck on discharge

When ingredient is released into the bag, there must be some means of allowing the displaced air out. (See diagram above.) For non-dusty products this may not need to be more than a conduit through the fillhead to a dust sock. For more dusty ingredients, or hazardous, or sanitary applications a venting arrangement will be attached to the conduit to suck the expelled air into the plant’s air filtration system. A fan, or an eductor may be used.

Vibration, during and after filling produces a stable, densely packed bag. It eliminates under-filled bags and allows bags to be safely stacked 3 high on, or, off pallets. However, the means by which vibration is applied, the timing, and its combination with a tamping action, may be critical to filling the ideal package. (See below, Coned Lift Table and the Filling Cycle.) The bulk density of the ingredient in a filled bag should be as near as possible to its tamped bulk density. The bottom of the bag should be supported during initial filling, and the ingredient should then be directed into the bottom corners of the bag for ideal shape and to ensure a straight bag side.

Control and Metering uses a patented Coned Lift table which forces the ingredient to the bottom corners of the bag. The coned vibration table descends, the center column of ingredient collapses and levels the ingredient, producing highly compacted corners and a flat surface. Low frequency, high amplitude provides maximum tamping, medium frequency low amplitude vibration provides maximum densification.


Hang weighing ensures a low dead load because only the bag and the bag support arms are weighed. This delivers high accuracy, and stable weighing. It also protects, to some degree, the load cells from fork lift contact and avoids deterioration of performance associated with washdown. Control and Metering machines deliver accuracy to within 0.15% of target weight.

Gross weighing (with load cells weighing the entire machine and the bag and the ingredients) may be satisfactory in some cases. Weighing may not be required, at all.

Microprocessor filling-specific controls promote operator ease and repeatability. Filling controls should be programmable to suit the particular application. Empty Bag Tare, Target Weight. Fast and Dribble feed, Densification Timing, Liner Inflation, Table Up and Down Functions etc. are all programmed through an easily accessible keypad, usually located to the rear of the filling machine.

The control panel housing relays, starters, terminals etc., should also be fitted to the machine and be accessible.

The operator should never be positioned under a bag, nor be required to conduct any functions above his/her head. All operator functions should be conducted at chest level. A platform should be provided to ensure the operator has complete control, visual and physical, of rigging and liner positioning procedures. All filling controls should be easily accessible at all times during filling. The structure of the filling machine should be sturdy, as simple as possible, with the least amount of crevices to present for cleaning.

Frequently, a filling machine is used to fill bulk bags of differing heights. In some cases, the intervals when a certain single bag height is being filled is sufficiently long that a fifteen minute procedure with a fork lift operator is acceptable. In other applications, different bag sizes or a mixture of perhaps drums and bulk bags present to be filled alternately, one after the other, and automatic bag height adjustment can be a vital benefit to the flexibility of the filling system. Control and Metering offers filling machines which supply either possibility.

The ability to accumulate two or more bags before needing a fork lift truck to takeaway filled bags is often important. Roller conveyors and motorized conveyors can be an integral part of Control and Metering machines. Further automation can be achieved by adding slip sheet dispensers or pallet dispensers to the unit. The ultimate in automation is our Carousel filling station which is capable of filling up to 70 one-ton bags an hour. It can eliminate the requirements for pallets and provide just-in-time production possibilities saving on warehousing, labor and transportation costs.

Control and Metering acknowledges that each enterprise will have specific requirements to fill bags in the most efficient and cost-effective manner. We have considerable experience in, not only assessing the client needs, but in designing and engineering the best solution for the task. We offer customized equipment, including machines which fill bulk bags, drums and Gaylord’s. Swivel fill head configurations to increasing output, residue free fill heads, special hand pallet roll-on designs are among some of the innovations we regularly supply.

As a result of identifying these basic principles and applying them to equipment design, Control and Metering is in an excellent position to provide filling equipment with the necessary sophistication to meet the challenging demands of sanitary and hazardous applications.

Please contact us for further information.

B & H Industrial Products, Inc.
PO Box 68004
Indianapolis, IN 46268
317.872.5806 | 317.875.5649 Fax