Bearing systems for grinding rollers in vertical roller mills and high-pressure roller presses; part 1

摘要

The grinding rollers are the key components in every vertical roller mill and high-pressure roller press. The basic requirement for reliable operation is optimum configuration of the bearing system and of the immediate surroundings of the bearings. This article provides an overview of the most important bearing designs and the associated issues relating to specific bearings, including calculation of the bearing life, structural configuration of the surroundings of the bearing, lubrication and bearing sealing. Although not all the designs available on the market can be shown here the explanations and design principles can also be applied to the bearing designs that are not explicitly mentioned. Due to the nature of the system the bearings in vertical roller mills are usually located inside the grinding area and the bearing outer ring rotates with the grinding roller with a static shaft. In contrast to this the rollers in high-pressure roller presses have bearings located in a mechanical support outside the grinding area. Self-aligning bearing systems are needed in this case due to the nature of the design; this is taken into account by using self-aligning roller bearings or an appropriate housing design. The bearing is dimensioned by determining the calculated bearing life as specified in ISO 281. Special calculation programs are used to take account of particular operating conditions and to determine the correct bearing clearance and component deformation. Lubrication by oil circulation has the advantage that the oil can be filtered and supplied at the required temperature. The purpose of the sealing system is both to avoid leakage and to provide protection against the now hot, abrasive, mill feed. The bearings in high-pressure roller presses are often lubricated with grease and the grease serves not only for lubrication but also as a seal. The latitude in design means that a wide variety of labyrinths and shaft sealing rings can be used but a certain self-aligning capability must always be taken into account. In spite of the application of proven design guidelines and methods of calculation the support system for grinding rollers still remains a challenge for designers and the manufacturers of rolling contact bearings even after decades of experience.