Patent ID: 7856337
Filing Date: 2010-12-21
Classification: G01P

Abstract:
1. A method of monitoring the rotational speed of the shaft of a gas turbine having a pre-determined number of spaced blades on or rotating with the shaft, and wherein the blades each have a tip and the tips of the blades can move relative to each other, the method including monitoring blade time periods between successive blades as the successive blades pass a sensor, and deriving a correction factor associated with each blade time period for correcting future sensed blade time periods; wherein the method includes the steps of: i) providing a sensor for sensing movement of said spaced blades; ii) determining a current blade time period between the passage of successive spaced blades past the sensor; iii) deriving the correction factor for said blade time period by: iv) determining the rotational speed by dividing the sensed current blade time period by the correction factor derived for the equivalent blade time period in a previous revolution of the shaft.