Miniature test techniques for life management of operating equipment

Life management of operating equipment is always a preferred way for maximising its operating life effectively and safely. Many novel test techniques, based on hardness or indentation methods, are used for assessing the material properties of the equipment to ensure its safe operation. The novel test techniques are correlation based indirect test methods to provide tentative material properties, which help in determination of residual life of the equipment. In comparison to these indirect test techniques, residual life estimate based on miniature test techniques are unique and precise as they give direct material data from the equipment. This is achieved by conducting destructive test of miniature test specimens, which are made from the material scooped out from the operating equipment. The critical issue is reliability and acceptability of these results from miniature test specimens in absence of any international standards. Considerable work is going on in this direction for making the miniature test techniques as standard test techniques, which will make it acceptable to all concerned enabling them to exploit many of its advantages. Even though various applications of miniature test techniques are found in literature, this paper discusses one of the important industrial applications of the technique which is in the field of life management of operating equipment. Due to lack of standardisation, there are many issues with the miniature test techniques, which must be addressed prior to its application in any area. This paper discusses the issues with some of the miniature test techniques, viz. tensile test, fatigue test and small punch test techniques. These issues have been addressed using experimental, analytical and metallurgical methods to make the techniques suitable for application in life management of equipment. At the end, scope of application of miniature test techniques in development of a new material, named as functionally graded materials (FGM), has been discussed.