INTRODUCTION

The stationary components of the steam path are not subject to the same level of stress as a consequence of rotation and centrifugal loading. However, they can still be in a high temperature/high pressure environment and will therefore be subject to loads sufficient to affect their operating life. In addition, the alignment these components are able to maintain relative to the rotating components during their operating life can be affected by steam conditions and various operating characteristics. When some form of deterioration is found in stationary components (and possibly progressing to an unacceptable level), it is necessary to evaluate the situation and to take corrective action. To undertake such correction, procedures must be developed.

It is necessary to develop and assess suitable procedures for both monitoring and correction so that at each outage the various affected components can be examined, critical dimensions recorded, and a non-destructive examination (NDE) of critical regions undertaken. These condition reviews should be an integral part of all outages. Any nonconforming condition must be monitored so the condition can be corrected when deterioration has occurred to the extent the unit cannot be returned to service without continuing to operate at risk, or with a significant reduction in the operating efficiency.

Two major stationary components possess conditions that must be examined because corrective action is most often necessary the casing (including the gland seal housings) and the diaphragms, or stationary blades. (These stationary vanes are often referred to as partitions.) Both components can be subject to...