Paper Machine Dryer Bearing Reliability- Lubrication Issues

摘要

Paper machine dryer bearings rarely achieve a fraction of their design life due to lubrication causes, installation andrnoperating problems. The bearings are subjected to heating from steam within the journal. The temperature of thernbearing and the lubricant depends on the oil flow rate to each bearing. The elastohydrodynamic (EHD) lubricationrntheory can be used to determine a required oil film thickness to minimize wear, but oil (bearing) temperature mustrnbe known. Analytical methods of determining bearing temperature have been developed and validated with onmachinernmeasurements by several researchers. A dryer journal with a leaking steam inlet insulating sleeve can haverna 87 ℃ /(156 ℉) higher temperature than a journal with a non-leaking sleeve, with the temperature of the bearing'srninner race close to that of the journal. The oil flow rates recommended by major machine builders are sufficient torncool bearings with leaking steam inlet insulating sleeves and obtain acceptable oil film thicknesses. Other causes ofrnreduced bearing life include particulate contamination and water contamination which can be resolved by properrnfiltration and water removal.rnCase histories are discussed that illustrate problems caused by system design deficiencies, maintenancernshortcomings, and human error.