When milk is treated in an evaporator for the removal of water, scale in the form of "milkstone" builds up on the inside of the tubes, associated equipment, pumps and pipework.

The removal of milkstone is necessary to maintain operating efficiency, with the costs of removal being measured in labour, chemicals, production losses and increased energy costs due to reduced thermal efficiency. Other factors include reduced production efficiency, as a result of shortened production runs, increased corrosion, a shorter life for capital equipment and product wastage.

The SCALEwatcher ENiGMA System was installed at a creamery belonging to a major dairy group. The System was installed on the stainless steel pipes, varying in size from 2 to 4 inches, on the discharge side of 11 pumps feeding various stages of the evaporators.

The purpose of the trial was to evaluate the System for its effectiveness in reducing milkstone and scaling within the evaporators.

Records were kept over a period of 12 months and during that time it was noted that the feed valve, used to maintain the flow rate as milkstone deposits built up, was consistently open below 40% instead of the previous 100%. The production cycle was increased by 25% and the rinse cycle was decreased by 60%. Records were also kept of how quickly "A Grade" milk powder could be produced after cleaning, and it was noted that the time decreased by 60%.

It was observed that there was no increase in the level of insoluble particles in the product and there had been no measurable change in product quality.

When the plant changed from whole milk to skimmed processing only one wash was required instead of two.The evaporator was opened after only three weeks operation and it was seen that there was less scale than normal. A later inspection indicated that the small amount of scale remaining was soft and crumbly.

Savings on detergents, milk losses and energy alone have been calculated at around £23,000 per annum.

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