Spiral freezer
Also known as: spiral IQF freezer, spiral belt freezer
Short definitionA belt-type blast freezer for continuous lines. The belt winds tier upon tier around a drum inside an insulated enclosure, and the product on it freezes as it travels through fast air at around −35 °C; it needs little floor space.
If the production line delivers product without a break, a blast room with trolleys interrupts the line. In a spiral the product enters at one end, travels a helix of 20–40 tiers and is taken off frozen at the other end. Because hundreds of metres of belt are gathered on a small footprint, it takes far less room than a straight tunnel. The air is between −30 and −40 °C. Time in the freezer is set by belt speed; thin patties come out in 20–30 minutes, chicken pieces in 40–60 minutes.
It is recommended for products whose shape must be kept, such as meatballs, nuggets, fish fillets, pastries and pizza; for peas and sweetcorn a fluidised-bed IQF tunnel is the better choice. The load calculation starts from the temperature at which the product enters. The low evaporating temperature calls for a CO₂, economised or two-stage system and an evaporator with wide fin spacing. Frost build-up means a break for defrost and washdown after 16–20 hours of running. If the air balance at the infeed and outfeed openings is not set up, the enclosure draws in warm air.