Paper Machine Dryer Bearing Reliability- Lubrication Issues, 2004 Paper Summit, Spring Technical & International Environmental Conference, (including Papermakers; Process Control, Electrical & Information; Product & Product Quality)

Paper machine dryer bearings rarely achieve a fraction of their design life due to lubrication causes, installation and operating problems. The bearings are subjected to heating from steam within the journal. The temperature of the bearing and the lubricant depends on the oil flow rate to each bearing. The elastohydrodynamic (EHD) lubrication theory can be used to determine a required oil film thickness to minimize wear, but oil (bearing) temperature must be known. Analytical methods of determining bearing temperature have been developed and validated with onmachine measurements by several researchers. A dryer journal with a leaking steam inlet insulating sleeve can have a 87 oC /(156 oF) higher temperature than a journal with a non-leaking sleeve, with the temperature of the bearing’s inner race close to that of the journal. The oil flow rates recommended by major machine builders are sufficient to cool bearings with leaking steam inlet insulating sleeves and obtain acceptable oil film thicknesses. Other causes of reduced bearing life include particulate contamination and water contamination which can be resolved by proper filtration and water removal.

Case histories are discussed that illustrate problems caused by system design deficiencies, maintenance shortcomings, and human error.