Ice formation in the frozen and chilled food industry causes familiar but unwelcome problems. Munters IceDry® humidity control has once again successfully tackled the root of the problem by removing the ice within the volumetric fill process of Unilever’s well-known Birds Eye frozen peas production.
Volumetric fill equipment dispenses product into a pack, by having a container that is filled with product and then passes over a hole to release the product through the chute into the packaging.
The frozen peas journey starts when they leave the cold store and pass via the chilled area, where they are sorted and graded, to the ambient temperature weighing and bagging area. As the peas pass rapidly between the different temperature conditions the peas experience the dewpoint effect of air around the peas creating condensation which rapidly freezes forming ice crystals. There is also ice creation due to moisture migration within the peas reaching the surface. This snow builds up on the surface and can get really bad on humid days.
A number of problems arise: the ice build up forming internally on the filling tube constricts the flow of peas into the bags. The cause of the ice was that the tube was colder than the air being pulled through and consequently, moisture was condensing out onto the internal surface of the tube and forming ice. This problem was exacerbated by the fact that ice particles from the peas themselves were adhering to the formed ice, in the same way that a snowball is made, and reducing the tube diameter even further.
On cup and collar mechanism, this ice formation prevents free movement of the cup to alter volume which leads to increased ‘give aways’. The other benefit of the Munters IceDry® desiccant dehumidification system is the reduction of “give aways” on the volume head of the weighing machine. The ice build up made the balancing less controllable, and therefore to ensure that Unilever met the required volume levels, the filling machine was set prior to installation of the Munters IceDry® humidity control system, to slightly overcompensate for this ice created control loss.
Both these issues cause productivity inefficiencies due to production downtime, which is measured by Unilever as “non planned stoppages” in order to return the line to production by removing the ice build up on the tube, cup and collar and repairing any mechanical damage caused by large ice pieces.
Munters had already installed solutions within the freezer and cold store areas in the Unilever group and together with the Unilever team, investigated a desiccant dry air solution to eradicate this ice build up.
The solution was to provide very dry air, at a dewpoint lower than that of the product. This dry air was introduced into the top of the head to flood the filling machine. This prevented the possibility of ice build up from the air and from the product. This ensured effective movement of the cup and collar mechanism. Now with dry air the control can be set more accurately reducing the give aways.
Prior to application of the Munters IceDry® dessicant dehumidification solution, the removal of ice could take typically 15 minutes or in some instances up to 1.5 hours.
This has been a highly successful application, which has shown a reduction of non-planned stoppages to near zero levels. The effect as stated by Grame McColl Hind, Project Engineering Manager, was “You go in there now and you just don’t see ice”.
This application has been so successful that the Unilever team have recently won a Silver TPM (Total Productive Maintenance) European Award within the group, as audited by the Japan Institute of Plant Maintenance for innovation in process control, which included this dramatic reduction in non-planned production stoppages.
Munters IceDry® desiccant dehumidification application has also been successfully applied to multi-head weighing machines to prevent block freezing, deterioration and ensure accurate weighing. This is part of Munters overall IceDry® humidity control concept, which has been used in freezers to dramatically increase throughput and in cold stores to improve safety and product storage quality.