Cooling and Lubrication of High-speed Helical Gears

Centrifugal compressor and turbine manufacturers are building machines that operate at increasingly higher speeds to reduce the size and cost of their equipment. Helical gears are commonly used to step down the speed of these machines to match nominal motor and generator speeds. The demand for higher compressor and turbine speeds has resulted in an increase in the maximum pitch line velocities of helical gears. Gear manufacturers have also increased the allowable tooth loading to reduce the size and cost of their equipment. The increase in pitch line velocities and tooth loadings has not been without problems. Several new and updated American Gear Manufacturers Association (AGMA) standards have been published to educate end users on the issues with high-speed helical gears and to provide consistent criteria for rating gears. One of the key issues is lubrication and cooling. The purpose of this paper is to present some of the current methods for evaluating the lubrication and cooling requirements of high-speed helical gears to assist end users with selecting new gears and to provide a tool for solving gear problems.