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Tank cleaning efficiency

24 September 2008

A cheese processor has increased the efficiency of its raw milk tank cleaning operations by 35% while reducing water usage by 30%. Here's how.

Llandyrnog Creamery, owned by Dairy Farmers of Britain (DFB), is set among the rolling hills of North Wales. Despite its idyllic rural setting, it has an output of hard cheeses such as Cheddar, Double Gloucester and Red Leicester: 20,000t leave the site each year for supermarkets and small retailers in the UK. To maintain this level of production, Llandyrnog processes 1 million litres of milk each day.

Raw milk is stored in six 160,000l capacity silos which are cleaned daily. The Creamery's CIP (Cleaning In Place) routine involves a pre-rinse using water recovered from the final rinse, a hot wash with a 1% caustic solution, an intermediate rinse with fresh water and a sterilant phase followed by the final rinse using fresh water. Water is drawn from the creamery's own boreholes and an average 400,000l is required each day.

The CIP regime was originally devised for fixed spray balls, which were installed at the same time as the raw milk silos in 1974. As Brian Emmerson, Llandyrnog's chief engineer puts it: "They weren't so much state-of-the-art as State of the Ark; nowhere near as efficient as we wanted and wasteful of water and energy."

The fixed spray balls cleaned the silos by deluging the interior walls with large volumes of water. This was very water and energy intensive with shadowing occurring in areas where the water lacked sufficient force to dislodge accumulated product. The large volumes of water involved also put a strain on the CIP system's pump and it was frequently necessary to stop and start it to scavenge the tanks between each cleaning stage.

DFB has invested more than £3 million at Llandyrnog since it took over the creamery in 2004. As part of the improvement programme it reviewed its raw milk storage arrangements and decided the raw milk storage CIP operation was in need of upgrading. Originally, it took one Toftejorg Sani Mega rotary head on trial but the results achieved in the test silo were so positive they rapidly installed the same equipment in the remaining five silos.

In stark contrast to the deluging action of spray balls, Alfa Laval's Toftejorg Sani Megas clean, to a predetermined pattern, through impingement and high levels of turbulence, scrubbing the silo's internal walls with fan shaped jets that cascade down to produce a vortex action once they reach the bottom outlet. Drive is provided by the medium operating an internal turbine and gear system at low speeds (5rpm) which enables the cleaning process to be controlled with great accuracy.

According to Brian Emmerson, the creamery was able to reach optimum-cleaning efficiency rapidly once they had the Sani Megas properly set up. "As soon as we had the system configured we saw the difference. For a start, we noticed the pre-rinse phase went from opaque to clear running much more quickly than before, which indicated we were using smaller volumes of water.

"Then, the same happened with the caustic phase and the intermediate rinse and so on. Basically it was a cumulative process with a good reduction in chemicals and water at each phase of the CIP cycle that resulted in less energy and water usage and greater cleaning efficiency."

Since they were installed, the Sani Megas are, in fact, said to have achieved sufficient savings in energy, time and water usage to pay back the original investment. Cleaning times have been slashed from an average 43 minutes to 28 minutes per silo. As importantly, the standards of cleanliness have seen similar improvements.

Total viable count (TVC) and other standard test procedures now demonstrate much higher levels of hygiene while shadow areas have, the company says, been eliminated.

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