The following is the second entry in a four-part series by John Wallace (AST’s Vice President of Operations) focused on bearing choices in medical technology. Click here for part 1, featuring bearing materials, and look for future updates including surgical/dental tools and laboratory/diagnostic equipment.
Lubricant selection may be the specification most overlooked by designers and engineers. Bearing life depends on proper lubrication in terms of both type and amount. In many cases, miniature and smaller instrument bearings are lubricated once for the life time of the device. Thousands of greases and oils are available that are designed to function in a variety of conditions and environments.
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. In the world of medical devices, bearing lubricants are subjected to sterilization, temperature extremes, high speed rotation, saline wash down or irrigation, chemicals and reagents, blood, and radiation.
Lubricant selection not only depends on the operating conditions the bearing will face, but may also be subject to regulatory requirements. Manufacturers of medical devices are often required to use what are known as food-grade lubricants, which are broken into categories based on the likelihood they will contact food.
H1 lubricants are food-grade lubricants used in food processing environments where there is some possibility of incidental food contact. H2 lubricants are used on equipment and machine parts in locations where there is no possibility that the lubricant or lubricated surface contact food. Finally, H3 lubricants, also known as soluble or edible oil, are used to clean and prevent rust on hooks, trolleys, and similar equipment.
Due to the wide array of products, price, and availability, both a lubrication specialist and the bearing manufacturer should be consulted before making a final lubricant selection.
To read the article in full, click the link below and the article begins on page 97.