NONCONTACT VIBRATIONAL MEASUREMENT TECHNOLOGY OF STEAM-TURBINE BLADE

One of the important ways to increase reliability of a power plant is to measure the vibration of steam turbine blades during operation. The measurement of the rotating blades is usually executed by a strain ga ge; however, since the turbine has multiple stages, it is generally di fficult to attach the strain gages to the rotating blades and obtain s ignals from the gages, especially in the intermediate stages. Furtherm ore, gages and wiring must endure high centrifugal force of rotating b lades, steam pressure, and moisture in the turbine under operation. Th is paper presents noncontact measurement technology which measures the vibration of the steam turbine blades during operation using a laser beam installed in a stationary casing. Furthermore, this paper delinea tes technical problems in the measurement of the steam turbine blades, such as the severe environment in which light is irregularly reflecte d, the durability of sensors, and small amplitude due to the shroud bl ade.