M-SB1 Single Belt Bagging Machine

Why a belt and not a gate?

In a gate machine, product pours freely through a flap that opens and closes. With small, round grains such as cereals this is no problem. A large lump of coal, however, can catch in the gate opening and stop it closing; pellets get trapped against the edge of the closing gate and break. The dust and fines this creates spoil the look of the bag and turn into quality complaints from pellet buyers.

On the M-SB1, product drops from the hopper onto a belt that carries it to the weigh hopper. Flow is set by belt speed rather than by the size of a gate opening. At the start of filling the belt runs fast, it slows as the target weight approaches, and the last grams are completed with a slow stream. With no sharp edge cutting through the product, breakage falls, and large pieces travel along the belt without jamming.

M-SB1, M-DB1 or a gate model?

• M-SB1 instead of the gate M-SF1: if your product is coarse, angular, fragile or sticky, you need belt feeding. The two machines have similar output; the difference is how the product enters the machine. Because of its belt mechanism, the M-SB1, at about 1,700 kg, is somewhat heavier than the M-SF1.
• M-SB1 instead of the double-belt M-DB1: the M-DB1 reaches up to 750 bags per hour and is a larger machine with a 3000-litre hopper and a weight of 2,300 kg. If your hourly target stays below 400 bags, the M-SB1 takes up less space and one belt is quicker to maintain.
• When is it not enough? If the daily target goes beyond 2,500–3,000 bags in a shift, the pace of a single belt is at its limit; then it is time to look at the double-belt model.

Points to watch for each product

Pellets: with wood and feed pellets the main loss is breakage. Belt feeding reduces it, but the height from which pellets fall into the hopper matters too. Keeping that drop short at the hopper inlet completes the benefit the machine provides.

Coal: with coal of mixed piece size, large lumps and fines can separate on the belt. Keeping the hopper steadily full helps the belt deliver a similar mix to every bag. Because of coal dust, dust extraction around the filling spout should be considered.

Pumice: pumice is light and abrasive. Being light, 25 kg of pumice takes up far more volume than 25 kg of grain, so bag size and spout are chosen accordingly. Because it is abrasive, the belt surface and scrapers should be checked more often.

Reading the capacity correctly

The table gives 250–400 bags per hour and two capacity ranges, 8–10 t/h and 9–10 t/h. The number of bags changes inversely with bag weight: light bags approach the upper end, heavy bags the lower end. For example, 400 bags of 25 kg an hour make 10 tonnes. When planning, the soundest approach is to look at a few shifts of real data after commissioning, so that the density and flow of your own product are taken into account.

A simple shift calculation: if 7.5 of 8 hours are net running time and 250 bags of 50 kg are filled per hour, the day ends with 1,875 bags, or about 94 tonnes of coal or pellets.

Installation and maintenance

The belt motor and control system call for a three-phase mains connection (400 VAC, 50–60 Hz) on site. The bag holder and filling mechanism are pneumatic: the air line must deliver 8–10 bar, and the table bases this on a 300-litre compressor. The top hopper holds 1800 litres, and this volume can be changed to suit. The machine is placed under a silo or at the outlet of an elevator or conveyor that brings the product. On a pellet line the machine is often fed from the cooler and screen outlet; the hourly flow coming off the screen should then be assessed together with the machine’s capacity. At coal yards, an intermediate hopper above the machine filled by loader is a common arrangement.

On a belt machine, maintenance centres on the belt. Belt tension and tracking should be checked weekly and product stuck to the belt cleaned off. A slack belt slips when it speeds up, and the approach to the target weight becomes erratic. At the end of the shift, fines and dust inside the weigh hopper should also be removed; any build-up in the hopper is added to the weighing.