This system was labour intensive but suited conditions in Egypt where labour was plentiful One factor to recognise with any system using trucks and trays is the necessity of providing a good hardened floor surface, treated against acid and alkaline attack and the wear and tear of truck wheels passing over continuously. It is a good precaution to lay steel tracks flush with the floor surface, where the trucks pass through the stoves in the drying compartments, and extend them out to the loading and unloading areas, and the riffling space between the dryer heat zones The cabinet dryer is essentially a small batch tray dryer, suitable for any product being dried on a pilot scale, or small production level They are usually of 10 or 20 tray capacity, each tray measuring 813mm by 406mm by 30mm deep. The trays are supported in the cabinet on angle brackets at the sides spaced 75mm apart, with one tray per level in the 10 tray dryer and two at each level in the case of the 20 tray unit. The heat source may be steam or electricity and is located at the side of the drying compartment-a fan provides a cross-flow of drying air. TUNNEL DRYERS emicontinuousa orporate the tray drying technique of the stove dryer on a semi continuous basis. They can be designed to give a viable commercial throughput and, as stated at the beginning of the chapter are still used in America and Europe, in some of the older factories As the name implies, the drying chamber consists of one, two or sometimes three tunnels, rectangular in section, up to 12m in length, with a loading aperture sufficiently large to allow the entry of trolleys, which carry the drying trays in racks up to 1. 8m in height. The trays are racked in pairs on each shelf of the trolley. Double Tunnel Dryers This type of dryer was developed in the UK in 1940 for a programme of vegetable dehydration under the auspices of the Ministry of Food. A typical double tunnel unit comprises awet tunnel and a 'dry tunnel running Parallel. The dryers set up by the ministry were some 10 7m in length, and the heat source was gilled steam tubes with the fans positioned aft, so that air was drawn through the heater bank and blown through the tunnel The trolleys entered the wet tunnel sideways, locating on a track fitted with a pusher device. In the first position, the trolley was sufficiently far away from the fan to permit adequate diffusion of the hot air stream to avoid ScOreThis system was labour intensive but suited conditions in Egypt where labour was plentiful. One factor to recognise with any system using trucks and trays is the necessity of providing a good hardened floor surface, treated against acid and alkaline attack and the wear and tear of truck wheels passing over it continuously. It is a good precaution to lay steel tracks flush with the floor surface, where the trucks pass through the stoves in the drying compartments, and extend them out to the loading and unloading areas, and the riffling space between the dryer heat zones. The cabinet dryer is essentially a small batch tray dryer, suitable for any product being dried on a pilot scale, or small production level. They are usually of 10 or 20 tray capacity, each tray measuring 813mm by 406mm by 30mm deep. The trays are supported in the cabinet on angle brackets at the sides spaced 75mm apart, with one tray per level in the 10 tray dryer and two at each level in the case of the 20 tray unit. The heat source may be steam or electricity and is located at the side of the drying compartment - a fan provides a cross-flow of drying air. TUNNEL DRYERS Tunnel dryers incorporate the tray drying technique of the stove dryer on a semi continuous basis. They can be designed to give a viable commercial throughput and, as stated at the beginning of the chapter, are still used in America and Europe, in some of the older factories. As the name implies, the drying chamber consists of one, two or sometimes three tunnels, rectangular in section, up to 12m in length, with a loading aperture sufficiently large to allow the entry of trolleys, which cany the drying trays in racks up to 1.8m in height. The trays are racked in pairs on each shelf of the trolley. Double Tunnel Dryers This type of dryer was developed in the UK in 1940 for a programme of vegetable dehydration under the auspices of the Ministry of Food. A typical double tunnel unit comprises a ’wet’ tunnel and a ‘drf tunnel running parallel. The dryers set up by the Ministry were some 10.7m in length, and the heat source was gilled steam tubes with the fans positioned aft, so that air was drawn through the heater bank and blown through the tunnel. The trolleys entered the wet tunnel sideways, locating on a track fitted with a pusher device. In the first position, the trolley was sufficiently far away from the fan to permit adequate diffusion of the hot air stream to avoid scorching the product. 67