Failure Prevention Procedure of the Very Large Telescope Hydrostatic Bearing Pads Based on the Lubricating Film Thickness Measurement

Abstract Maintaining a uniform film thickness is crucial for ensuring the safety of hydrostatic bearings in telescopes. If the lubricating film is disrupted, it can lead to the collision of sliding surfaces, resulting in costly and time-consuming repairs. Since hydrostatic bearings enable the telescope movement, repairs interrupt observations. By monitoring film thickness, potential errors in specific bearing pads can be detected and addressed at an early stage. The current film thickness measurement method, using dial indicators, is applicable only under static conditions and can be influenced by human error when setting or reading the values. In contrast, using contactless sensors provides a more reliable and efficient method, ensuring higher safety for hydrostatic bearing systems. However, factors such as working conditions and the number of required sensors need to be considered. In this study, field tests were conducted to evaluate the current dial indicator method and simulate the effects of clogged capillary errors. The proposed contactless sensor setup was also tested under real conditions on bearing pads. The results indicate a potential approach for interpreting telescope movement scenarios. Given the serious consequences of bearing failure, regular monitoring of film thickness should be prioritized to mitigate the risk of significant damage.