Recent Developments in Methods to Study Creep Strain Variations in Power Station Steam Plant

In power station steam plant, experience has shown that portable monitoring equipment is ideal for reliable point-to point measurement of creep strain and also acquisition of strain mapping information. On going laboratory tests have shown positive initial results in that direction; the results being validated against metrology standards. In addition to the monitoring of in-service strain in steam pipes, the study of the effects of strain distribution across welded pipe sections and other known early failure locations on steam pipes and other plant components is growing in interest. An existing strain monitoring method employs the E.ON UK ARCMAC gauge system with a capability of both uniaxial and biaxial strain measurements. For strain mapping, digital image correlation (DIC) is also incorporated and integrated with the ARCMAC system. In an effort to further improve the ARMAC system portability, the use of a digital single-lens reflex (DSLR) camera system is investigated. The scope of a combined ARCMAC/DIC system to provide for both point-to-point and strain mapping of piping features is studied. Identification of a feature using a combination of ARCMAC and DIC techniques is presented here. Additionally, the investigation of an edge-finding technique which can complement the existing ARCMAC system is presented.