Component deterioration is observed in fleet gas turbine units during overhaul and maintenance activities of utilities providing electric power, co-generation or mechanical drive operations. Affected components include those provided by Original Equipment Manufacturers (OEM) and newly-manufactured and repaired hardware from OEM or aftermarket suppliers. This study details: i) the gas turbine flow path component deterioration and distress typically observed from operation, ii) some of the typical reasons (expected and abnormal) for the component damages, iii) the resulting effects and detriment to the utilities, and iv) a means for reducing the potential for component damages and operational risk to the utilities.
Abnormal gas path component deterioration is one of the leading causes for forced opening of IGT units. Unscheduled opening of production gas turbine units during normal and critical operating time periods can result in significant costs to the utilities and insurance providers due to unplanned overhaul and maintenance costs, replacement components costs, and lost production revenue during the outage. Often the majority of the premature component deterioration within a set can be attributed to the quality of manufacturing or repair processing and inadequate inspections of the components.
Escapes in quality assurance can occur resulting in components being supplied to utilities that do not meet design intent, such as debris contamination, coatings issues, and mis-machined features. Additionally, component suppliers are often pressured to meet production deadlines and provide delivery of the components to the utilities to avoid contractual penalties. This scenario can result in the potential for reduced focus on the quality of the components and quality-control escapes of design-deviated components delivered to the utilities for unit operation. Any uncontrolled deviations, damage, and discrepancies that result from hardware manufacturing and repair processes can have a significant impact on the long term durability of turbomachinery components. These component “damages” and manufacturing defects can be reduced or eliminated through proper functional quality inspections and component assessment, prior to unit installation. Additional issues concerning, improper tooling and methods employed during component removal and re-installation during maintenance activity can also result in damage to components and premature deterioration.
This study focuses on how utilities can perform or audit the functional checks on components prior to unit installation in an effort to reduce component degradation, operational risk and potential of forced outage of units resulting in additional maintenance costs and lost revenue.