Refrigeration Key in Moving Milk
September 3, 2007
Schools face special challenges when it comes to commercial refrigeration, particularly when it comes to the safety of milk. Because of safety regulations at the state and national levels, temperature guidelines for milk in schools are more rigid than those faced by supermarkets, convenience stores, and restaurants. Milk for school use must be kept at or below 41°F and most manufacturers of refrigeration equipment prefer to be below 41°.
There are refrigeration technologies available to meet the strict needs of schools. Original equipment manufacturers (OEMs) and contractors at all points of the milk production and distribution process count on such refrigeration equipment to protect their reputations.
FROM COW TO COOLERThe first point of the commercial milk refrigeration process happens when the cows are milked. Taken from the cow, the milk is cooled down to 33° and stored at that temperature. Manufacturers specializing in this type of refrigeration look for three key attributes in the equipment they use: reliability, efficiency, and durability.
One such manufacturer, the Paul Mueller Co. stresses state-of-the-art equipment and uses Copeland Scroll® compressors (made by Emerson Climate Technologies) in its products. “Such technology has cut our failure rates by more than half,” said Mike Kelly, product manager, dairy farm equipment at the Paul Mueller Co.
KEEPING COOL ON THE ROADTransit is perhaps the most vulnerable point for the milk in terms of temperature changes.
Because of this, manufacturers of refrigeration transport equipment like insulated truck bodies and design their products to cool the milk at around 36°. Hercules Manufacturing, makers of such truck bodies, stresses reliability and energy efficiency.
According to Jeffrey Caddick, purchasing agent for Hercules Manufacturing, the best-case scenario for keeping the milk at ideal temperature occurs when the milk is moved from the processing plant and placed directly onto the insulated truck bed. This minimizes any temperature change the milk might experience and ensures the longest possible shelf life for the milk.
The temperature of the milk as it leaves the processing plant is not always uniform. Sometimes it is 33-34°. At other times it might be closer to 39°, which is getting too close to the 41° mandatory minimum for OEMs to feel comfortable.
Considering that dairies usually load their trucks a day before transport, the role of the insulated truck body becomes not only maintaining temperature overnight and during transport, but also reducing the milk’s temperature outright to attain goal temperatures of 36° and below.
Compressor reliability here is vital, as the average dairy transport truck carries approximately 5,600 gallons of milk - a great deal of mass for a refrigeration system to cool. The refrigeration systems must be comprised of components capable of serving such large loads and maintaining a temperature within one to two degrees of the 36° target.
IN SCHOOLFor the most part, school districts do not purchase milk coolers for their buildings. Instead, milk distributors provide coolers to the schools free of charge in exchange for the right to be a district’s exclusive milk vendor. Once inside the school, the cooling equipment must meet the harsh reliability and durability requirements of schools. In an environment where the cooler is generally left open for a minimum of two hours every day, the schools count on their equipment to keep the milk at safe temperatures.
Nor-Lake makes coolers that are often used in schools and have found that the most important facets that schools need for their refrigeration equipment are reliability, ease of use and ease of cleaning. “Schools generally can’t afford to hire specialized contractors to maintain their refrigeration equipment, it’s usually someone who does a little bit of everything,” said Roger Bauer, engineering manager at Nor-Lake.
“That’s why they want something simple that they can just count on and not really have to think about.”
For Bauer, the condensing units in the coolers need to have very low failure rates. Technical support also is important. “For our coolers, we sometimes have very specialized requests and Emerson (the condensing unit supplier used in this case) has done a great job of accommodating us,” he said. “If we say we’re building coolers that need to keep milk about 35° even with the doors open, they’ll work with us to make that happen.”
The reason that reliable milk refrigeration equipment is so vital throughout the distribution process is simple: happy, healthy kids. For many children, school may be the only place where they can get milk to drink, making it even more important that the milk be safe and that all of the vitamins and nutrients vital to healthy children are retained. An important part of the process is the best possible refrigeration components inside the systems.
Publication Date: 09/03/2007