Once assembly is complete, an application should undergo a test run to determine that all components are operating properly. During a test run, the bearing(s) should run under partial load and, where there is a wide speed range, at low or moderate speeds. A rolling bearing should never be started up unloaded and then accelerated to high speed, as there is a significant risk that the rolling elements will slide and damage the raceways, or that the cage will be subjected to impermissible stresses.
Any noise or vibration can be checked using an SKF electronic stethoscope. Normally, bearings produce an even "purring" noise. Whistling or screeching indicates inadequate lubrication. An uneven rumbling or hammering is in most cases due to the presence of contaminants in the bearing or to bearing damage caused during mounting.
An increase in bearing temperature immediately after start-up is normal. In the case of grease lubrication, the temperature does not drop until the grease has been evenly distributed in the bearing arrangement, after which an equilibrium temperature is reached. For additional information about running in of grease lubricated bearings, refer to Running in of grease lubricated bearings.
Unusually high temperatures or constant peaking indicate that the preload is too heavy, that there is too much lubricant in the arrangement or that the bearing is radially or axially distorted. Other causes could be that associated components have not been made or mounted correctly, or that the seals are generating too much heat.
During the test run, or immediately afterwards, check the seals, any lubrication systems and all fluid levels. If noise and vibration levels are severe, it is advisable to check the lubricant for signs of contamination.