Degrees of Separation

The latest separator equipment is built for efficiency, durability and, increasingly, capacity.
by Lynn Petrak
It’s one of the oldest and most essential points in dairy production. The separation process, in which different liquids and solids are separated from each other in a large tank or centrifuge, is the virtual starting point for milk, cheese, ice cream, dairy powders and other dairy products and has been, since separators were first introduced in the 1890s.
If not done correctly, the final product will not be formulated properly, and if done too slowly or inefficiently, a plant’s profitability can suffer due to lost volume, energy costs or operating time.
With separation at the beginning phase of the production process playing such a key role, suppliers are updating separators with state-of-the-art features and technology. There may not be many new models of separators rolling out every year and although there are only a handful of separator manufacturers in the United States, changes are being made to meet processors’ demands for reliability, speed, efficiency, durability and volume. “It’s the most integral and expensive piece of equipment in the plant. It’s the Swiss watch, if you will,” says Mark Etcheverry, sales manager for Statco Engineering and Fabricators, Huntington Beach, Calif., which sells and reconditions separators for dairy customers around the country.
Because so many industries rely on this pivotal equipment, leading separator suppliers continually refine their technology and equipment features. In addition to dairy processing plants, separators can be found in other food and beverage facilities, from juice plants to breweries, as well as various industrial environments, ranging from oil drilling to pharmaceutical manufacturing to wastewater treatment.
As in those other industries, dairy processors are seeking equipment that will enable them to do things better and quicker, as capacity demands increase and as product lines broaden. “For some of the larger dairies, the capacities are going up, and there has also been the consolidation of dairies,” says Jeff Biel, product manager, separation and filtration, for Tetra Pak, a Vernon Hills, Ill.-based packaging and production equipment supplier that distributors a line of separators, including Alfa Laval machinery. “They want to do more and do it efficiently.”
That was exactly what operators at California Dairies Inc., Artesia, Calif., were seeking when they decided to replace separators for powdered butter applications in three facilities during a plant remodeling project a few years ago. “We were looking for better skimming efficiencies and better energy efficiency. Machines today are more efficient when it comes to separating milk and cream,” recalls Harry DeLint, vice president of engineering, noting that the company chose Tetra Pak’s HMRPX 718 models, which have resulted in energy savings and more operator-friendly use. “All the fat we can get out of there and turn into butter, the better we are.” The new separators were placed between raw milk receiving and milk evaporation systems, with one high-capacity plant running four separators at once.
Tied into efficiency, of course, is the all-important concept of profitability. “Basically, and again with the pressure the dairy industry is facing, they need to look at their bottom line. If they put a piece of equipment in a plant, it has to save them money or increase their bottom line and we are doing that with better efficiencies,” says Biel.
An efficient separator system has an inherent financial benefit, adds Etcheverry. “It’s important, because with separators, you are separating the fat or part of it to sell products you have labeled to a certain fat content. Also, with the extra butterfat, you can sell that for profit,” he says.
A Solid Explanation
Separators have been used in the production of milk for more than a century, dating back to the first models developed by the brand that is now known as Alfa Laval. As milk varieties expanded, the need for more sophisticated separators also has grown, with processors separating and reintroducing milk fat for different fat-based product types.
During the separation process, a separator’s motor-driven centrifuge rapidly spins raw milk in order to remove heavier milk solids from the rest of the fluid and to separate the cream from the skim milk. For fluid milk, milk fat can be gradually added back in at various levels to make whole milk, 2%, 1% and other such varieties.
Separators are also used in cheese production for whey, a byproduct of the cheesemaking process. Cheese fines can be removed from whey through a centrifugal clarifier, with additional fat removed in a whey separator. Plants that manufacture dairy-based powders also utilize separators, to take out milk proteins during the drying process. Lactose, whey protein, casein and butter oil can all be recovered through the use of separation technology. On the quality and food-safety side, separators have been used for clarification purposes to help remove bacteria.
Separator sizes and types vary. While the basic engineering of a separator hasn’t varied much in the past few decades, some separators are larger today to accommodate growing capacity demands — up to 150,000 pounds an hour — while several are built with automatic software-based control systems. Separators are available as mostly as non-hermetic decanter centrifuges, which feature a natural settling action during the spinning process, and in some cases, as disc stack centrifuges. Separators are powered by motors that range in speed, while some separators include internal pumps for liquid removal.
Separators can also be adjusted for either hot-milk or cold-milk processing. During hot-milk separation, with temperatures ranging from 120 to 145 degrees F, a separator is used to separate the globular milk fat from the skim milk or serum, with the outgoing cream containing a high percentage of fat. Cold-milk separation, which takes place at temperatures from 39 to 46 degrees F, is less common but can be done with cold-milk separators, which tend to have special design features and lower capacities than hot-milk or warm-milk models.
Like so many other types of equipment investments, the preferred model of a separator depends on the operation itself. According to Etcheverry, most fluid dairy plants have two separators in use. “At manufacturing plants where they make powder or butter, they can have four or five,” he adds. Likewise, Biel estimates that many larger milk plants have up to three separators, while cheese milk processors can run as many as 18 units.
Prices for separators also differ, although they represent a larger investment for a dairy operation than other processing components, based on their function, size and complexity. Both Etcheverry and Biel, for their part, say that new separators can be sold from $300,000 to close to $400,000. Even as high-ticket items, separators are built to last, with many models lasting 15 to 20 years with minor adjustments and replacements.
Innovations and Enhancements
Every year or so, separator suppliers offer either new models or upgraded features for their equipment. Technology for separators today continues to focus on enhancing the crucial function and performance of separators, but also to allow for greater volumes and flexibility.
One example is Tetra Pak, which regularly develops new solutions for both the packaging and processing equipment side of its operations. In late 2003, Tetra Pak introduced its Tetra Centri™ 918 HGV, the latest separator that uses the company’s AirTight® technology. “It’s the largest separator in our product line,” says Biel, adding that the model was created based on both customer demand and emerging capability. “We increased capacity and boosted features of energy consumption. Our customers said, ‘We need a bigger one, but don’t want it to be an energy hog and need it to perform right.’” The new separator handles 10 percent greater volumes than the previous large models, the Tetra Centri H818 HGV with power consumption below 55 horsepower.
For dairy processors, much of the appeal of the Tetra Centri 918 separator is in its air-tight seal, which allows for a more gentle acceleration and separation of milk to prevent fat globules from being damaged and reduced in size. “We’ve always believed in the hermetically sealed design and have to keep adapting that type of separator for increased capacities,” says Biel, citing a few design upgrades for this particular piece of machinery. “We’ve maximized the design of the inlets and the bowl outlets to ensure maximum efficiency. And without getting too technical, there are certain components of a separator which are key in determining performance — we look at all those things, such as changing the size and design of the separator components.”
Beyond offering a skimming capability of 120,000 pounds of hot milk and 130,000 pounds of whey per hour, the Tetra Centri 918 is also versatile for industry manufacturers, who can use it for both separation of milk and whey and for both hot and cold applications. The models for those specific functions feature minor variations. According to Biel, plants investing in a larger separator also tend to upgrade other related machinery, including buying larger homogenizers and higher capacity pumps and valves to help run the equipment and keep up with the production pace and volume.
Hermetically-sealed separators like Tetra Pak’s Centri line represent the latest generation of separation technology. Another major supplier, Westfalia Separator Inc., Northvale, N.J., a member of the mechanical separator division of GEA, has invested in new technology for its customers. Last year, Westfalia added a new feature to its two-year-old line of HyVol hermetically sealed separators and clarifiers: the HyVol Protein Plus System.
An available option on new separators (and an addition that can be retrofitted to older models), the HyVol Protein Plus system allows separators to be discharged very two hours, resulting in shorter and fewer ejection cycles to help boost efficiency and save on energy costs. In addition, the system helps prevent milk from being lost in the production process.
Westfalia has also developed a new non-self-cleaning smaller separator model, the MTC-3. Designed for small dairies with a capacity of up to 600 liters an hour, the MTC-3 was built for a smaller footprint but includes features like a solid-wall disk-type bowl and a detachable hood.
All of Westfalia’s separators for dairy environments are also equipped with a “SoftStream” feed system to allow for the gentle processing of raw material. The company also has developed a patented process for the continuous recirculation of carrier liquid.
Other Separator Mainstays
While suppliers are working to roll out new separator models and accessories, other traditional types of separators remain popular among dairy processors. “Our most common separator would be our 618 model, which runs at a slower RPM. The inlet design allows for smaller flow rates,” says Biel, adding that the flow rate is about 70,000 pounds an hour for skimming applications. Like other Tetra Pak separators, the 618 is powered by a motor specifically engineered for the supplier.
The leading separator suppliers continue to be Tetra Pak and Westfalia in this country, along with other suppliers such as DCI Inc., St. Cloud, Minn.. Meanwhile, many companies specialize in the distribution of branded separators, both new and reconditioned.  df
Lynn Petrak is a freelance journalist based in the Chicago area.