TRI Resolution of Turbine High Amplitude Rotor Vibration Problem

Problem and Solution:

A utility has several identical 190 MW, 3600 RPM large steam turbine-generators with excellent heat rates and a vibration problem at certain loads (certain control valve positions). With the original bearings, it is not possible to balance the turbine rotors at all loads. The typical solution has been to operate the units at fixed loads near maximum generation. Because other units have to be turned down further or shut off at night, the resulting system costs are relatively higher. In 1995, TRI designed, built and installed a set of TRI Align-A-Pad® tilting pad bearings for the HP and IP turbines of one of these units. The rotor-bearing dynamic characteristics were changed so that the turbines can now be balanced at all MW loads. The new system exhibits lower vibration and reduced turbine losses. The system is now run by the Automatic Generation Control (AGC) and the overall average generation cost for the system has been reduced.

As this electric utility re-evaluates power sourcing and costs, units are being retrofitted with TRI Align-A-Pad bearings. Contact TRI with a description of your turbine-generator rotor vibration or bearing problems, and TRI will be pleased to provide you with a proposal for resolution. TRI offers performance warranties in most cases.

TRI Replacement of Older Fluid Drive Impellers and Runners Damaged by High Cycle Fatigue

Problem and Solution:

Most fluid drives installed in the U.S. were put into service in the 1960s. With increasing service life, fluid drive impellers/runners are beginning to fail via endurance limit problems. Also known as High Cycle Fatigue (HCF), an impeller/runner blade fails due to blade passing excitation frequencies that match the blade natural frequencies. The problem arises more when units are used in sliding pressure applications because the output shaft speed varies widely. Flaws in the material or other manufacturing defects can exacerbate HCF problems.

TRI has solved the HCF problem by manufacturing new impellers and runners using improved blade shapes, materials, and manufacturing techniques. With increasing probability of HCF failure of older units due to extended time in service, and because impellers and runners have long lead times, TRI recommends a spare rotating element or a complete spare fluid drive for critical service applications. If not possible, TRI recommends purchasing spare impellers and runners. Such spares permit a fluid drive assembly to be rebuilt quickly, minimizing the time that a utility is exposed to the prospect of purchased power at exorbitant rates.

For the most demanding applications, TRI manufactures impellers and runner with integral reinforcing rings, US patent 5,331,811.