ENGINE & TURBINE TECHNOLOGY
procedures also include changes in materials, coatings, or designs, which aim to improve performance and lengthen the periods between scheduled maintenance activities.
ASSESSING SERVICEABILITY Te basic operating principles of a gas turbine are relatively simple, but the components involved must handle high temperatures and work within very fine tolerances. Highly specialised parts and manufacturing processes are used to create the turbine’s components and these need to be properly maintained to ensure continued efficiency and reliability. Regular data collection from sensors
Large industrial gas turbines require spacious and well- equipped service centres
Campbell Archibald on optimising gas turbine performance through planned maintenance and repairs
WHY PLANNING PAYS OFF
G
as turbines are efficient and reliable sources of power that drive generators in national power stations as well as smaller industrial settings.
Teir flexibility allows them to be brought online to meet increasing demand for electrical energy and their reliability can be assured, providing an effective and well-planned maintenance programme is in place.
Te popularity of gas turbines across the world as a source of mechanical power emphasises the efficiency and reliability that can be achieved. Te range of designs from aero-derivatives to large-scale power generation units, means that a wide range of applications can be accommodated. Teir flexibility is enhanced by the capacity for frequent start/stop operations, but this makes planned inspection and maintenance all the more important, especially in applications with an increased risk of corrosion. Furthermore, higher operating temperatures and mechanical stresses are
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creating the need for the use of advanced technology components and refurbishment processes. In general, repair activities consist of the stripping and reapplication of coatings, the rebuilding of the geometry by welding, and the rejuvenation of the material condition through appropriate heat treatments. Advanced refurbishment
throughout the installation provides important information on vibration, temperatures, pressures and turbine output. Tis is collated and assessed to determine any anomalies as part of a serviceability report, which identifies the issues that need to be prioritised and addressed before they can cause significant damage.
Condition based monitoring and
recommended maintenance intervals are usually dictated by the original equipment manufacturer (OEM), however, these take a one-size-fits-all approach and may not suit some applications. Tis is especially true for gas turbines used for peak lopping or as back-up units; assets in these situations can benefit from remote monitoring and bespoke maintenance packages that take less common circumstances into account. Tis proactive approach is complemented
by upgrading the sensor package to use items such as sonic microphones in the hot gas path to indicate issues with the combustion process. A tailored package offers the best availability of the gas turbine by enabling maintenance and repairs to be completed during scheduled shut-down periods. Tese also offer the opportunity to install upgrades and improvements that can extend reliability and improve performance.
Gas turbines of all sizes require a regular maintenance programme to ensure their continued reliability
THERMAL INSPECTIONS At the heart of the gas turbine, hot gas path components require regular inspections since close examination of the individual turbine blades can reveal overheating issues. More obvious defects can be identified by a service engineer using a borescope, but occasionally a more detailed inspection may be required that demands more sophisticated tools. Te use of basic thermographic equipment can identify heat build-up in electrical equipment and bearings by using a passive detection system that relies
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