DAIRY FOCUS: David Cotton, Bridge Farm, Near Glastonbury

2nd January 2020

20,000-litre silo, Compact Glycol Water Chiller (CWC) and Heat Recovery Unit (HRU)

Over the years, the economics of milk production have encouraged the formation of larger herds with higher yields. So it was that David Cotton, whose dairy farm is at West Bradley near Glastonbury, was faced with the need to upgrade the milk cooling and storage part of his business.

23 years ago, when it was installed, David’s 9,000 litre milk tank was ample for the farm’s output, but now that he is milking 250 cows and producing 8,000 litres per day he found himself right on the limit of capacity and relying on daily collections.

“I knew we needed more capacity but my decision on the best solution coincided with an incentive from our milk buyer Arla, based around giving them more flexibility on milk collection times. That meant we would have to be able to store at least two days’ output in tightly controlled conditions,” David explains.

The solution, put together with assistance from T H White Dairy engineers, comprised a DeLaval 20,000 litre cooling tank, a compact water chiller (CWC), plate cooler and heat recovery unit. Unlike conventional cooling units, the CWC uses glycol which can be cooled more rapidly than water without freezing, at the same time consuming less energy. Milk from the line is first filtered and then fed to a plate cooler style of heat exchanger where the chilled glycol is used to pre-cool the milk. The milk then flows to the 20,000 litre tank where the milk is maintained in perfect condition at 4deg C. In such large tanks there’s a need to protect the quality of the first litres of milk that enter the empty tank, so the evaporators in this silo tank feature a unique lateral configuration that ensures milk quickly covers an entire evaporator plate for efficient heat transfer. Gentle internal mixing also ensures consistency of temperature throughout the tank.

At the same time the DeLaval heat recovery unit is able to recover up to 60 per cent of the heat extracted during the milk cooling process which then produces hot water for use in pipeline and parlour cleaning.

“It’s a perfect solution,” David enthuses. “In general we now have a milk collection every other day, but we have the flexibility to deviate from that if necessary – it has boosted our returns and it suits Arla, so good all round.

“Although we had been using it for 23 years, the old milk tank was still in excellent condition so we have retained that, giving us a total capacity of 29,000 litres of temperature-controlled milk. If the collection tanker happens to arrive during milking we can also divert the milk into the original tank while the new one is being emptied.

“The whole system was installed very neatly by a single T H WHITE engineer who made a beautiful job of it. We are impressed!”