Coal, Gas

Turbine blade monitoring system milestone

6 June 2005 – A new system that continuously monitors operating blades in gas turbines has surpassed 5000 hours of operation, confirming that the technology is ready for commercialization.

Developed by Siemens Power Generation, with funding from the US Department of Energy, the online monitor makes it possible for operators to replace turbine blades based on their actual condition, when the thermal barrier coating is worn or damaged. This capability optimizes the life of the blades, avoids the high cost of unscheduled replacement, and extends the time between preventative maintenance periods, increasing the availability of the plant.

The technological breakthrough could help keep electricity rates down by saving gas turbine utility operators an estimated $600m per year.

The first full-scale high-temperature, full-pressure commercial system was installed in a Westinghouse 501FD gas turbine at Empire Stateline Electrical Company in Joplin, MO, during a scheduled outage last October to demonstrate its capabilities in capturing real-time infrared images of rotating blades. Siemens engineers are monitoring the performance of the first row of thermal-barrier-coated blades on both pressure (front) and suction (back) sides.

The demonstration will evaluate the mechanical design and integrity of the blades’ thermal barrier coating, camera performance, environmental enclosures, spectral filter, integration and development of the supervisory system, and the life model that predicts when the thermal barrier coating on a blade will fail.

Turbine blades operate in an exceptionally hostile environment; they rotate at more than 3600 revolutions per minute, with a linear tip speed of 800 mph, under very high pressure (220 psi, nearly 15 times the force of gravity or about the same as under 450 feet of water) and extremely high temperature (in the range of 2600 ºF, about the melting point of steel).

To operate in these conditions, Siemens Westinghouse developed a cooled optical probe that is installed in the gas turbine reaching down to the moving blades. A near- and mid-wave infrared high speed camera is also situated in a cooled housing and connected to the probe outside of the turbine.