Digital Speckle Photogrammetry Techniques Applied to Monitoring High Temperature Steam Pipes

Digital Speckle Photogrammetry (DSP) is proving to be a very useful technique for studying, in the laboratory, the distribution of strain about cracks and other defects in stressed specimens. This non-contact technique is able to resolve strain gradients over a small physical area, for example across a weld heat affected zone. The technique has good potential for use as a condition monitoring tool for a variety of components in electrical power stations. In addition this measurement technique could also be applied to monitor the integrity of critical components of newer generation plant, such as wind turbine generator blades. There are, however, many installation problems to be overcome. For example, there is the need to have regard for the hostile environment in steam generating plant and the demanding conditions to which wind turbine blades are subjected. Ideally the outputs from individual DSP sensors would be used for continuous remote monitoring. However, DSP measurements can also be useful each time the plant is shut down during a plant outage; which would be used to complement data from existing proven rugged monitoring methods. This paper describes ongoing work to develop a ruggedised digital speckle ‘sensor’ and associated image capture system.