Such conditions in the Indiantown, Fla. plant pose a constant threat of contamination to the bearing units supporting the washers’ multiple shafts. Even the method of cleaning the washers — a high-pressure spray of water mixed with caustic soda — is potentially damaging. The powerful washdown can flush lubricant right out of the bearings.

Over the years, the brush washers have made short work of just about every traditional bearing solution — nickel-plated housings, cast-iron pillow blocks lubricated with grease lines, and pillow blocks with solid lubricant packs. No matter which method, most bearings failed within 9 or 10 weeks.

Finally, in an experiment 3 years ago, Caulkins installed two MRC composite mounted bearing units on one brush washer. Not only did the units work effectively for that entire season, they are still running today. The test was so successful that Caulkins purchased 120 of the composite units and is replacing all present cast-iron blocks.

Housing corrosion

“We had a tremendous problem with rusting of cast-iron housings,” says Joe Delisle, Caulkins maintenance supervisor. “The rust could flake off, and we’d have to replace the housing whenever it happened. But rust, of course, is not a problem with composites.”

The MRC unit is specially designed for the harsh environments of the food and beverage processing industry. Made of a reinforced polymer, the unit’s housing resists the corrosive effects of frequent washdowns and chemicals such as citric acids and cooking fats. And a double-protection seal guards the insert bearing.

How they run

During the 6-month processing season at Caulkins, the two brush washers clean more than 4 million lb of oranges and grapefruit daily. The fruit is transferred from a holding bin via conveyor to the washers, which are outside the plant. The washers move the fruit along to an elevator, which brings it inside for squeezing.

Each washer consists of about 30 long, horizontal shafts which rotate in the same direction and are equipped with brushes. Two bearings, one at either end, support each shaft. The washers clean and convey fruit simultaneously. As the fruit rides along toward the elevator, spray heads above the washers release a sanitizing shower composed of phosphoric acid and water. As the brushes rotate, they scrub the fruit.

“The washer bearing housings are continually exposed to contaminants,” says Mr. Delisle. “Citric acid from the fruit can wash into a bearing and harm the lubricant. And the sanitizing spray is extremely powerful.”

Trials

Metal bearing housings have generally succumbed to the severe conditions within a few months of installation. At one time, Caulkins used nickel-plated housings, a common option in the foodprocessing industry. In plated housings, a protective coating is bonded to all exterior surfaces of the base metal. But the coating has a tendency to peel or chip in the brush washer environment, according to Mr. Delisle, and exposure to food acids can turn it black. At Caulkins, nickel-plated housings soon corroded and had to be replaced.

Good for you; not for bearings. As citrus fruit travels on brush-washer conveyor toward elevator, it also gets a sanitizing shower. Brush-shaft bearings down below must take citric acid seepage plus phosphoricacid shower solution. New composite-housing bearing with double sealing keeps bearings from dying of excessive Vitamin C and cleanliness.

Another problem, lubricant contamination and subsequent attack on bearing running surfaces, also dogged brush washer bearings. A few years ago, Caulkins tried cast-iron pillow blocks lubricated by means of grease lines. As a special precaution against contamination, the bearing units were purged by regreasing manually every day, sometimes two or three times a day, increasing maintenance costs. Even so, the bearings failed within about 6 weeks.

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