This paper is focused on new methods of noncontact sensing vibrations and deflections of rotating machine parts, especially blades of steam turbines. Special attention is paid to the induction and magnetoresistive (MR) sensors developed in the Institute of Thermomechanics for noncontact measurements of characteristics of rotating blades inside steam turbines under operation. Different principles of noncontact sensors based on measuring deflections or velocity components are described and compared, including new types of MR sensors. Hitherto unpublished principles of sensors intended for shrouded blades are described and discussed.

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The paper is focused on new methods of non-contact sensing vibrations and deflections of rotating machine parts, especially blades of steam turbines. Special attention is paid to the induction and magnetoresistive sensors developed in the Institute of Thermomechanics for non-contact measurements of characteristics of rotating blades inside steam turbines under operation. Different principles of non-contact sensors based on measuring deflections or velocity components are described and compared, including new types of magnetoresistive sensors. Hitherto unpublished principles of sensors intended for shrouded blades are described and discussed.

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The study deals with the opportunities for the assessment of damage to blades in low-pressure steam turbine stages under operation. So far existing methods are based on measurements and evaluation of blade vibrations. Calculations of fatigue cycles are used as a basis for an estimate of the residual life of the blades. A new approach using the analysis of impulse blade signals generated by non-contact stator sensors was applied. Basis for the assessment of blade damage are static characteristics and mutual position of blades. Geometrical and mechanical characteristics of blades change due to creation and progress of a crack. The presence of the crack leads to a change in position between adjacent blades. This method has been applied and verified by long-term measurements at the nuclear power plant Temelin. Other static methods based on blade untwisting and elongation are suggested for monitoring the state of turbine blades.