Calculation of Friction Coefficients in Journal Bearings to Determine the Turning Gear Motor Power

Abstract

Steam turbine turning gear is a gear train, driven by electric motor, which is used to drive the rotor at a given speed and capable of breaking away the turbine and its load equipment from a standstill. Steam turbine rotor trains are supported by journal bearing which require lube oil for cooling. The normal turning gear operation requires that lube oil and the lift oil systems must be in-service in order to reduce the friction coefficient at the journal bearings during breakaway. The rotor train breakaway and running torque is the resisting moments at each of the journal bearings. The resisting moments at each journal bearing are functions of bearing loading, pad type, journal diameter and friction. Therefore, it is important to determine the static and dynamic coefficient of friction in journal bearings of the rotor system to design the turning gear motor power. In the present work, a detailed study has been made for calculating the static and dynamic friction coefficients in the bearings and validated the values with experiments for designing a suitable motor to run the rotor of a steam turbine.