Making Rotor & Bearing Alignment Moves EasilyOctober 5, 2010
A large number of bearings for steam turbines have “alignment pads” mounted on the outside of the bearing housing that seat against the bore of a pedestal or standard. Almost all of these alignment pads have only shims that move the pads in or out on the bearing, and these are used to make the bearing go up or down, or to the left or right. As a standard part of the alignment of a string of turbine rotors, the shims are changed and then the alignment blocks are “scraped in” by hand. This takes days to do, sometimes as much as a week.
TRI bearings use “alignment pads” with two types of shim packs: Type 1. standard radial shim pack that moves the alignment pad in or out, Type 2. two tangential shim packs, one pack on each side of the alignment pad. The use of both types of shim packs permits precise movement of the bearing housing in any direction according to a table of changes while maintaining full contact of the alignment pads on the pedestal bore without any hand scraping.
This feature adds cost, but it has shortened outages by several calendar days. We are told “they pay for themselves before the turbine is on line.”