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Spiral conveyors are divided into two types of products that take their name from their traction system: gearing spirals and drum spirals.
The choice of the spiral is taken each time depending on the type of treatment required, the type of product, the space available and the performance required, considering every single detail.
The gearing spirals take their name from the driving system which uses a pinion located on the outer circumference of the machine to make each level move. They are available with a AISI 304 steel belt or AISI 316 upon request. Each of these can have stainless steel or plastic mesh, with open surfaces variable depending on the dimension of the product. The width ranges from 350 to 1000 mm and the dimensions change depending on the maximum possible diameter, the number of levels and the shape. The shape can be circular or oval. Finally they may also have the reversal turn on the upper or lower side, so that between every lifting tier a dropping tier is located in order to make the loading and the unloading heights equal.
The drum spirals on the other hand transform the dynamic friction force, existing between the belt and the powered drum from a dissipative type force to a conservative one. The driving shaft placed on the linear section coming from the spiral connected to the “master” motor, moves the belt. The drum, a cylindrical-shaped stainless steel structure located in the centre of the spiral and around which the belt is wrapped, uses the friction strength generated to move the belt. In this case the belt choice is made considering the product dimensions, for which a 25 or 50 mm belt pitch is available, and the usage temperatures, which influence the choice between polypropylene or polyossimetilene, generally known as POM. Width ranges from 150 to 1000 mm and the dimensions vary depending on the maximum possible diameter, on the number of tiers and on the shape. The advantage of this type of machine is in the overall dimensions that, thanks to the much reduced space between the tiers, allows for much smaller dimensions and very high movement speeds.
Depending on the thermic treatment required, the spiral conveyor belts are dived into:
1 freezing spirals (box at –40,-35°C )
2 cooling spirals (box at –10,-8°C )
3 heap spirals (no box)
4 drying and pasteurizing spirals (box at +90,+98°C )
Boxes into which the spirals are inserted are built with sandwich-type panels having two sheets made of stainless steel or galvanized and pre-varnished steel, between which the thermoresistant material (of different thickness and type depending on the required temperatures) is inserted.
The thermic treatment units placed inside the cells guarantee temperatures and air conditions adequate for product treatment. It is therefore possible to control from the electrical panel both the temperature and the air speed. In the boxes with a negative temperature it is also possible to defrost the heat exchangers during production, avoiding any machine stoppages and therefore avoiding breaks in production.
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