Generator inspection and maintenance are two of the most critical measures for industrial gas turbines. These measures ensure that your equipment is functioning correctly while reducing the cost of repair to the owners. However, for this maintenance program to be effective, a number of factors have to be considered. This includes operating plans, operations priorities, personnel skills level, manufacturer’s inspection and maintenance recommendations, replacement parts, and other key factors determining the service life and operational efficiency of the equipment.
Three core reasons for effective gas turbine inspection and testing are reliability, efficiency and reduced operating costs. Essentially, gas turbines and their components are individually inspected and tested before being delivered to the owner. It is recommended to ensure a complete unit test of the gas turbine without the auxiliaries on and then tests the individual components for integrated functionality. Other components such as fuel gas filters can be used when testing both gas turbines due to their practicability.
According to new industrial rules on gas turbines, any newly acquired equipment shall undergo a qualification process that involves a more robust inspection and testing than the usual shop tests. During individual testing of gas turbine auxiliaries, mechanical integrity and performance are the two main checkpoints considered for key components. For instance, gas turbines can be tested for both — mechanical integrity to identify vibrations levels and performance testing to verify operating parameters according to acceptable international codes and standards.
Generally, a comprehensive gas turbine and generator inspection would involve five basic systems.
- Control and accessories
Testing and inspection of the controls and accessories are normally done in short duration outages, whereas the rest of the system components are serviced during long-duration outages. While the main focus of testing is usually on the combustion and turbine systems, other systems need to be included as well for comprehensive plant maintenance.
When it comes to generator inspection and repairs one popular method used is called borescope inspections. This process involves the inspection of the combustion chamber and gas turbine systems without removing the equipment casing. An optical borescope is inserted through any of the radially aligned holes on the compressor casings and displays the state of the internal hardware through a monitor connected to the boroscope.
Boroscope inspection is done in intervals and this depends on the operating modes and experience, fuels used, and the borescope inspection history. Boroscope inspection of gas turbines is effective in uncovering signs of compressor fouling, physical system degradation, cracks, dents, deformed of displaced components and other abnormal conditions.
Maintenance inspection of gas turbines and generators can be broadly classified into three:
- Running Inspections involves monitoring and observation of major operating parameters while a unit is running. It simply involves establishing initial operating data of a new gas turbine and after replacing major assemblies. Having the baseline data for performance can help measure unit deterioration after a period of time.
- Standby Inspection is conducted during off-peak when the unit is in-operational. The inspection involves routine service, repairing and replacement of accessory systems and device calibration. Operating parameters are assessed while the unit is operating.
Based on the inspection interval recommendations, which are determined by operating modes of a unit, the estimated repair and maintenance intervals could vary. More advanced technological upgrades are available that extend both inspection and maintenance intervals. Experts recommend part replacement when it doesn’t make economic sense to repair any part that is deteriorating.