Creep strain management of power plant components.

Extended life of power plant can only be achieved if it can be shown that the high temperature components have adequate residual creep life. There is often a significant margin between minimum assured creep rupture properties and the actual properties of a component in service. Regular strain monitoring can demonstrate quantitatively that components are fit for extended service and enable utilities to capitalise on this margin. Hitherto, however, widescale application of high temperature strain monitoring has been prohibitively expensive, technically difficult and unreliable in practice. A method of creep life management of high temperature pressure components is described, employing different means of measuring strain which become more focused and refined as creep life exhaustion progresses. Initially, widespread use is made of a direct strain measuring system, employing low cost gauges or ''targets'' capable of operation at temperatures ranging up to dull red heat - circa 600 degrees C. The targets are read intermittently at room temperature by a diode array ''camera'', the ''reading'' including universal time and date and a target identifier. This information passes directly to a database, maintaining the integrity of the recorded information and minimising the possibility of errors. As creep strains approach unacceptable levels, the system has identified the most appropriate components and locations for continuous strain measurement, employing capacitance gauges. It has also prioritised components for plant replacement.