Packing Frozen Vegetables without Ice Build-up

Achieve Faster filling, Accurate weighing and Less stoppages


Packaging of frozen vegetables

Frozen vegetables such as peas, carrots, broccoli, etc are typically packed in volumetric filling equipment. Multihead weighers are one such type of this equipment often used in NZ. This type of machine dispenses products into a pack by first feeding the product into the  top of the multihead weigher where it is dispersed to the pool hoppers. Each pool hopper drops the product into a weigh hopper beneath it as soon as the weigh hopper becomes empty. The weigh hopper becomes empty when the correct weight is achieved. Necessary for this process is the smooth flow of the product into the chutes and machinery free from ice. 


Why does ice occur?
 

Usually the packaging of frozen products is done some distance from the cold store. Thus,  the air in the packing area usually has a higher dew point than the product temperature  and also the now cold packing equipment (i.e. multi-head weighers). The higher dewpoint causes condensation on product as well as equipment.

What is dew point?

Dew point the saturation temperature for water in air. The dew point is associated with relative humidity. A high relative humidity implies that the dew point is closer to the current air temperature. Relative humidity of 100% indicates the dew point is equal to the current temperature and that the air is maximally saturated with water. So for example if the air is at 15˚C and it has a dew point of 15 C the relative humidity would be 100%, i.e. completely saturated. armer air can hold more moisture than colder air and at temperatures below the dew point, water will leave the air and condense on surfaces. So, if we were to cool our air from 15˚C to 5˚C we would get condensation forming on surfaces as 5˚C air can hold a lot less moisture than air at 15˚C .

Why do I get ice on product and surfaces?

When the product moves away from the cold store, it usually enters areas which are warmer in temperature. The product (usually frozen) also quickly works to cool down the surface temperature of packing equipment (multi head weighers). Thus the air around the product and packing equipment is also cooled. As we have mentioned above, the air in the packing area typically has a  higher dew point than the product temperature and the equipment.

As the air is cooled, the max dewpoint of the air is reduced and so the excess moisture condensates
and quickly freezes forming ice on both the products and the equipment.

Why is this a problem?

Ice forming on the cup and collar mechanism (for releasing the product to the packing) and the chute impedes its operation and result in uneven feeding to the package.

What is the solution?

To prevent icing on the product and equipment, the areas which the products passes through and the area where the packaging is done should be dehumidified to a dew point lower than the product temperature. Alternatively the conveying can be done via an enclosed tunnel and dry air with low dew point is then supplied to the tunnel and packaging equipment directly to prevent icing.

 

Contact us to find out what solution would work best for your site.