Since the early nineties a strong trend towards gas turbine application for power generation may be noticed. Decreasing gas prices in connection with high efficiency in combined cycle mode and small staff required made this technology attractive compared to the traditional coal based power generation. From the late nineties, advanced gas turbines have become available with power rates even more than 250 MW with about 40 % simple cycle / 58 % combined cycle efficiency. This great development could only be achieved by applying advanced technologies and materials available.
Gas turbines usually use fluid-film bearings for both radial and axial shaft support and generally employ conventional lube oil and seal oil auxiliary systems, featuring heavy construction. These devices often have a direct-coupled, integral power turbine that extracts all the energy needed to both drive the compressor section of the turbine and transmit torque to the driven equipment through an output shaft.
As always, nothing is gained for free. The more complex the machines got, the higher the turbine inlet temperature was pushed, the more exotic cooling techniques and materials had to be applied, resulting in an increased risk for abnormal behavior with the threat of non-availability on the horizon. Without reliable health monitoring systems to actively monitor and protect machinery’s health, power generation may encounter severe problems. As turbine or generator health degrades, performance decreases, generation declines, and even unplanned shutdowns may occur.
Use of vibration and process control parameter monitoring and machinery protection systems on large rotating machines has long been recognized as a valuable tool in the prevention of component and machinery failure. Several international standards have been developed exclusively for gas turbine’s protection and monitoring. Some of these standards have been summarized here for introduction: API 616, API RP11 PGT, API 670, ISO 10816-4, and ISO 7919-4.
In accordance with the mentioned standards, Vibsens has developed a specific condition monitoring & protection system customized for gas turbines and generators. In addition to the mentioned above requirements, a complete set of useful monitoring parameters and display functions have been added to increase the efficiency of the maintenance policies and regimes to ensure the continued good health of the power generating assets and to detect underlying problems early. Moreover,Vibsens condition monitoring system integrates machinery health data to process control parameters, allowing the user to correct issues before they affect power generation.
- Gas Turbine Condition Monitoring
A detailed layout from main measurement points usually used in Vibsens gas turbine condition monitoring systems is depicted bellow. Each of these measurement points are described in further detail.