Question: “We recently received a shipment of L10-rated bearings. Can you explain the meaning of the L10 designation?” Rotating-element bearing manufacturers measure reliability using a “load–life” calculation rating known as the L10 rating life. To achieve this rating, the manufacturer assumes the bearing will be run in a clean operating environment that provides an adequate lubricant film (adequate described as a film equal to, or greater than, the composite roughness of the two mating surfaces) of the correct viscosity for the designed maximum bearing speed and operating temperature ratings. The L10 rating is given to bearings manufactured with cleaner, degassed…