To read part I (introduction) of this series, click here.
To read part II (regulatory environment and safety) of this series, click here.
Lubricant selection is critical to bearing performance and life, yet it is often overlooked by designers and engineers. Bearing life in the harsh environments found in food processing depends on proper lubrication in terms of both type and amount.
Thousands of greases and oils are available that are designed to function in a variety of conditions. Operating temperature is the primary consideration when selecting a lubricant. Temperature directly impacts the base oil’s viscosity, which in turn impacts the ability to support loads.
Lubricant selection not only depends on the operating conditions the bearing will face, but may also be subject to regulatory requirements. Manufacturers of food processing machinery are often required to use “food-grade” lubricants. These lubricant types are broken into categories based on the likelihood they will contact food. The USDA created the original food-grade designations — H1, H2 and H3 — and the designations are described as follows:
H1 lubricants are food-grade lubricants used in food processing environments where there is some possibility of incidental food contact.
H2 lubricants are lubricants used on equipment and machine parts in locations where there is no possibility that the lubricant or lubricated surface contacts food.
H3 lubricants, also known as soluble or edible oil, are used to clean and prevent rust on hooks, trolleys and similar equipment.
Lubricants should provide good wear and corrosion resistance. Lubricants used in high-temperature applications such as meat, poultry, fruit-vegetable and beverage processing should have high-temperature oxidation stability.
Machinery used in beef, pork and poultry processing is typically exposed to “wash down” conditions using high-pressure water and anti-bacterial solutions which are often caustic, or steam, which can displace the grease. To avoid grease displacement, grease with high resistance to water washout are used and fill 70-100% of the bearing (as opposed to a typical fill amount of ~30%). While this level of filling can negatively affect rotational speed, it significantly improves grease life.
H1 lubricants used in these environments typically have synthetic, hydrocarbon base oils with urea, polyurea or aluminum complex thickeners. H2 lubricants typically have mineral or PFPE base oils with calcium soap or PTFE thickeners. Polyurea greases typically perform well in smaller ball bearings.
Solid lubricants can be used in very demanding applications. These are oil-filled polymers, or grease and polymer mixtures that solidify once heated and cooled. Solid lubricants can eliminate problems with grease leakage and emulsification when water is present.
Due to the wide array of products along with price and availability, both a lubrication specialist and the bearing manufacturer should be consulted before making a final lubricant selection.
There are a wide range of lubrication options to take into account for optimal application performance. Food processing engineers and designers are advised to consult a bearing applications specialist for assistance to best navigate these regulations. If you have a question regarding lubrication in the food industry (or any industry!) click here to pose it to our experts.
AST’s series on food and beverage bearing considerations will continue on December 11 with an in-depth look at materials options.