Nondestructive Evaluation of Gas Turbine Blade Cooling Holes Blockage by Thermography

Turbine blades are one of the most sensitive and important hot parts of gas turbines, so that the efficiency and life of turbines are directly related to the operation of these components. Therefore, to prevent damage caused by high temperatures, they must be properly cooled. The common method of cooling these parts is to pass the cooling fluid through their complex internal channels. Non-destructive testing of thermography, is one of the new methods for detecting imperfections in these cooling paths which is considered in this article. Thermal loading is applied in an active manner by hot steam generator system. In order to identify the capability of this system in the detection of the residuals in the cooling system of blades, 3 kinds of different blades are studied and tested using active thermography. Results show the appropriateness of the system in detection of the blockages in all three blades. But it worth to notify that the success of the system is strongly related to the best detection of the system parameters as steam pressure, temperature and Fluid flow. So, the best parameters are chosen as: pressure of 2bars, ambient temperature of 25 oC and the maximum fluid of the hot steam.