wheat flour and other cereals 25 Ik handled flour normally passes gh a system, like that in Fig. 2. Metering systems are described in Manual 2 on dough mixing, Biscuit doughs Flour is taken from the bottom of a silo, or after a sieving system, via a rotary seal into a stream of air and is blown to a hopper which is mounted on a weighing system, probably above a mixer The rotary seal is necessary to prevent the air in the conveying pipe blowing up into the silo. The flour is taken out of the air at the hopper because the hopper is designed as a cyclone. The flour/air mixture is fed in at the edge of the conical shape and as it swirls round the flour falls out and more or less clear air is blown out at the centre of the top The cyclone separates the flour from the air by two mechanisms. The first is centrifugal force and the second is because the air speed suddenly becomes much lower in the larger space of the hopper. Separation of the flour is very effective. The air is taken from the cyclone by a pipe that either returns to the silo and passes through the filter there or passes into a special filter. It is common to return the air to the sile because in this way, using a diverter valve, excess flour can also be returned. This allows the hopper to be filled quickly and, at the moment that the weight is made, the valve closes the feed and sends any excess flour into the line back to the silo. If a signal to stop the feed of flour from the silo only stopped the rotary seal under the silo there would be a long delay while the flour in the line cleared and the system shut down. Also the weight arriving at the hopper would be our shna 2 Bulk handling of flour, sugar and fatsWheat flour and other cereals 25 Bulk handled flour normally passes through a system, like that shown in Fig. 2. Metering systems are described in Manual 2 on dough mixing, Biscuit doughs. Flour is taken from the bottom of a silo, or after a sieving system, via a rotary seal into a stream of air and is blown to a hopper which is mounted on a weighing system, probably above a mixer. The rotary seal is necessary to prevent the air in the conveying pipe blowing up into the silo. The flour is taken out of the air at the hopper because the hopper is designed as a cyclone. The flour/air mixture is fed in at the edge of the conical shape and as it swirls round the flour falls out and more or less clear air is blown out at the centre of the top. The cyclone separates the flour from the air by two mechanisms. The first is centrifugal force and the second is because the air speed suddenly becomes much lower in the larger space of the hopper. Separation of the flour is very effective. The air is taken from the cyclone by a pipe that either returns to the silo and passes through the filter there or passes into a special filter. It is common to return the air to the silo because in this way, using a diverter valve, excess flour can also be returned. This allows the hopper to be filled quickly and, at the moment that the weight is made, the valve closes the feed and sends any excess flour into the line back to the silo. If a signal to stop the feed of flour from the silo only stopped the rotary seal under the silo there would be a long delay while the flour in the line cleared and the system shut down. Also the weight arriving at the hopper would be 2 Bulk handling of flour, sugar and fats