Ultrafiltration is a rigidly controlled “cleaning” or filtering process that removes microscopic particulates from synthetic oil and grease.
Ultrafiltered synthetic oils and greases were first developed for the military. However, more stringent demands for quality, reliability, and long operating life have made ultrafiltration a requirement for many other types of applications, typically those where particulate matter can jeopardize the operation of miniature and high speed devices. For example, Nye regularly ultrafilters synthetic oils and greases for precision bearings - in disk drives, navigational gyros, high speed dental drills, or positioning equipment used in vacuum chambers - where any solid contaminant greater in diameter than the EHD film that separates the bearing from the race can damage one or both surfaces. Other products that are routinely ultrafiltered include optical gels, disk coating fluids, and lubricants for micro-switches.
Ultrafiltration is not just an ordinary, post-production filtering process. Standards of cleanliness are clearly defined by the US government for both oil and grease. MIL-STD 1246 includes five cleanliness levels for oil: 50, 25, 10, 5, and 1, where each number refers to the largest particle (in microns) allowed in an oil. There are three cleanliness levels for grease. Unfiltered grease can contain particles larger than 75 microns. Filtered or "clean grease" cannot have any particles larger than 75 microns, and there must be less than 1,000 particles per cubic centimeter between 24 and 74 microns in size (MIL-G-81322, Aircraft Grease). Ultrafiltered or "ultraclean grease" must not have any particles larger than 35 microns, nor may it have more than 1000 particles per cubic centimeter between 10 and 34 microns in size (MIL-G-81937, Ultraclean Instrument Grease). Included in the ultrafiltered category is a new standard for optical gels. They may not contain any particles larger than 25 microns and must have no more than 50 particles per cubic centimeter, none larger than 24 microns.
Nye offers ultrafiltration services in a Class 100 environment for our own synthetic oils or greases - and for those of other manufacturers, which continues to be a sizable portion of our operations.
To determine whether your application would benefit from an ultrafiltered synthetic oil or grease, submit the Lubricant Samples and Questions Form or contact us.
Related Technical Articles and White Papers
Ultraclean Lubricants: A Specialized Process for Critical Applications