How it works
A milk cooling tank is a double-walled stainless steel vessel. Refrigerant runs through the evaporator between the two walls and draws heat from the milk without touching it, while the agitator brings every part of the milk to the same temperature and keeps the fat evenly spread. If the two do not work together, part of the tank never reaches the target.
The target comes from regulation. Article 55 of Türkiye's Regulation on Specific Hygiene Rules for Food of Animal Origin requires milk to be cooled immediately after milking, to no more than 8 °C if it is collected daily and no more than 6 °C if it is not; on arrival at the processing plant it may not exceed 10 °C.
Capacity follows the collection interval
The tank has to hold all the milk that builds up between two collections. For the same herd the volume changes with collection frequency, so the calculation starts from milk measured per milking, not from the number of animals; on routes where collection can slip, one milking is added as a margin.
| Collection pattern | What the tank must hold |
|---|---|
| Two milkings a day, daily collection | Two milkings |
| Two milkings a day, collection every other day | Four milkings |
| Three milkings a day, daily collection | Three milkings |
Cooling speed is part of the tank's type designation. Under ISO 5708, a type 2 II two-milking tank brings half its rated volume from the first milking down from 35 °C to 4 °C in 3 hours, and after the second milking is added it brings the mix back to 4 °C in an hour and a half. A pre-cooler reduces that load, and washing after every emptying keeps the starting bacterial count of the next milk low.