1. Fluid Bed Freezers
Fluid Bed Freezers have tended to be used historically for vegetables and fruit products, though they are now being used in certain areas of the Fish Industry.
2. Inline Freezers
These normally constitute a single belt or multi belt application, the air is blown horizontally across either a plastic or metal conveyor belt. Some specialist applications use stainless steel bands. Inline freezers are used for capacities up to approximately 400 Kg/Hr, with a product density of up to 6 Kg/m2. It is worth mentioning at this point that with this size of installation it is common to use direct expansion, single stage refrigeration plates. This type of refrigeration plant is relatively cheap, and uncomplicated. These type of freezers are used in developing countries, and have been much sought after within the respective Fishing Industries.
3. Spiral Freezers
The Spiral Freezer is a device which utilises a collapsible belt, so instead of having a long straight conveyor, a conveyor belt of considerable length is wrapped around a drum. This drum rotates, giving a friction edge drive to the belt. The Spiral freezer is used for product loadings of 2 Kg/m2 up to 10 Kg/m2, and in capacities of 400 Kg/Hr upwards. The Spiral freezers have been manufactured with belts in excess of one kilometre in length. The belt is supported and guided in a Helix around a rotating central drum. the belt tension increases as you go up the tiers exponentially to the eight tier, and thereafter attains a constant value. It is important that the tension in the system does not become too high. The advantage of the Spiral freezer is that it enables a high capacity to be achieved on a given factory floor area.
4. Boxafreeze
In considering the freezing of bulk packed meat products, the Boxafreeze is used commonly within the Meat and Poultry Industries. Boxed materials can be processed by contact plate freezers or air blast freezers. It is interesting to record, for instance, that different markets have evolved using the different methods, i.e. South Africa tends to use horizontal plate freezers, whereas New Zealand uses air blast freezers.
A typical freezing time for a poultry installation would be 3.5 hours, and some of the larger Boxafreeze installations are freezing in excess of 10 tonnes of chicken per hour on a continuous basis. The freezing time for a 150mm typical meat block would be in excess of 11 hours, this is why it is often considerably more desirable to use plate freezers instead of automatic Boxafreeze installations. The disadvantage of horizontal plate freezers is that they are generally a manual operation, whereas a sophisticated PLC control Boxafreeze is a fully automated in-line process machine.
It is worth noting that automatic horizontal plate freezers have been developed (Autoplate models), however are subject to high manufacturing costs compared to the standard horizontal plate freezer (cheapest) and Boxafreeze options.
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