An important aspect of the design phase has the engineer establishing the dimensional requirements of the various components comprising the steam path, the tolerances within which they are to be produced, and the material to be used. In addition to these obvious requirements, surface finish must be defined, special process procedures possibly identified, and the total quality (conformance level) to be achieved.

During original component manufacture when a component outside normal tolerances is produced, or when a nonconforming situation occurs during assembly it is the design engineer's responsibility to evaluate the condition and provide a disposition that will help ensure the unit meets its expected performance levels.

A nonconforming condition is one in which the existing elements no longer meet design requirements, i.e., individual components have deteriorated in their mechanical properties or surface and dimensional requirements. They have probably lost surface material, and no longer comply with the requirements established by design.

If deterioration is found at a maintenance outage, it is again the responsibility of a design or plant engineer to rule on the condition and develop an acceptable disposition. However, in this case, the disposition may not return the unit to the same condition it possessed as a new addition to the system. While such a disposition may return the unit to an acceptable condition perhaps even possibly long-term reliability it may also compromise efficiency. Often this has to be the case until a final disposition possibly involving the provision of replacement parts can be implemented.

Subsequent evaluation...