Milk cooling tanks

Every dairy farm in Holland is required to have a milk cooling tank. Immediately after the milk is derived from the livestock using the milking machinery it has to flow into a storage tank where its temperature needs to be lowered to and maintained at 4° C.

What is a milk cooling tank made of

A milk cooling tank, also known as a bulk milk cooler, consists of an inner and an outer tank, both made of high quality stainless steel. Attached to the inner tank is a system of plates and pipes through which the refrigerant fluid/gass flows. The refrigerant withdraws heat from the tanks content (e.g. milk). Every cooling tank comes with a generator set with a condensing unit which circulates the refrigerant and conveys the withdrawn heat to the air.

The space between the outer tank and the inner tank is isolated with polyurethane foam. In case of a power failure and an outside temperature of 30° C, the content of the tank will warm up only 1° C in 24 hours.

To facilitate an adequate and rapid cooling of the entire content of a tank, every tank is equipped with at least one agitator. Stirring the milk ensures that all milk inside the tank is of the same temperature and that the milk maintains homogene.

On top, every milk cooling tank has a manhole of about 19" diameter, this enables thorough cleaning and inspection of the inner tank if necessary. The manhole is covered by a lid and sealed watertight with a rubber ring. Also on top are 2 or 3 small inlets of about 1.5-3". One of these is covered with an air-vent, the other(s) can be used to pump milk into the tank.

At the bottom, every milk cooling tank has a 2" threaded outlet, usually including a faucet.

A milk cooling tank usually stands on 4, 6, or 8 legs. The legs are adjustable, enabling the tank to stand solid on every kind of floor, completely water-level. The built-in tilt of the inner tank ensures that even the last drop of milk will eventually flow to the outlet.

All tanks have a thermometer, allowing for immediate inspection of the inner temperature.

Most tanks include an automatic cleaning system. Using hot and cold water, an acid and/or alkaline cleaning fluid, a pump and a spray lance will clean the inner tank, ensuring a hygienic inner environment after every time the tank is emptied.

Last but not least every tank has a control box, basically it manages the cooling process by use of a thermostat. The user can turn the system on and off, allow for extra and immediate stirring, start the cleaning routine, and reset the entire system in case of a failure.

Recently, that is the last 10 years, more and more tanks have been equipped with a monitoring and alarm system. This system has several tasks.It guards the temperature of the milk inside the tank, it checks the functioning of the agitator and the cooling unit, and it checks the temperature of the cleaning water. In case of malfunctioning of any of these functions, the alarm will activate. The monitoring system will also keep a record of the temperature and of all malfunctions during a given period. These data can be transferred to a PC for further analysis.

For milk only?

Because all approved milk cooling tanks are produced in accordance with the ISO 5708;1983, IDT standard for milk cooling tanks, both the inner and the outer tank are highly finished, that means hygienically polished. Furthermore, this standard requires the use of high-quality stainless steel, either AISI 304 or AISI 316 stainless steel.

Because of this superior quality, milk cooling tanks are excellents tanks to be used in other hygienic environments than farms. HAGRA has sold tanks to numerous other food processing industries such as bakeries, consumption ice factories, fresh vegetable processing factories, slaughter-houses and more. In these cases the tanks contained either water, ice-mixes, flavor-additives, color-additives, blood and more. Also other industrial branches are working with former milk cooling tanks. HAGRA clients include printing-offices, chemical plants, cosmetic businesses, medical industries, and much more... Virtually any fluid can be stored in a former milk cooling tank and its price is comparitively low, when balanced against a new custom-built tank.

For cooling only?

Besides cooling, former milk cooling tanks can also be used to heat a fluid or simply to keep it isolated and warm/cold. See storage tanks for further information on this issue.