A gas turbine is a sophisticated piece of equipment that operates under extreme temperatures and pressures. It should be inspected and repaired in a timely manner to avoid breakdowns, accidents, unscheduled downtime and other negative developments. Furthermore, periodic inspection and verification are usually required by equipment manufacturers and environmental organizations.
On average, an inspection should be carried out every 8000-12000 equivalent operating hours. A specific period for each gas turbine unit depends on the manufacturer, class, operating conditions, type of combustion chamber, burner, etc. On average, it should happen every 1–1.5 years.
Types of inspections
There are several types of inspections, depending on the complexity, amount of work and frequency:
This type consists of inspecting the combustion chamber, blades, compressor inlet and hot gas path. No turbine disassembly is required at this stage. The inspection is carried out using a borescope (therefore, A-inspection is also called the borescope inspection). The main purpose of this procedure is to assess the general condition of the equipment and to determine the scope of work for subsequent, more detailed inspections, as well as to make recommendations for the operation of the unit. Minimal tuning and calibration of the turbine components can be performed during the A-inspection.
B-inspection involves a more detailed inspection of the hot gas path and the chamber, as well as some maintenance work. However, for some types of gas turbine units, B-inspection is no different from A-inspection and can also be performed using only a borescope without any disassembly of the unit. For other turbines, according to the maintenance regulations, it is necessary to replace some parts of the gas outlet and the combustion chamber. The final decision is made by the commission based on the results of the inspection.
C-inspection involves the largest amount of work. During the C-inspection, also called the main inspection, a complete disassembly of the turbine is carried out. It is followed by an inspection of the compressor, of all internal components, of the protective and control equipment elements and of the devices that monitor the operation of the gas turbine unit. Diagnostics of the main gas turbine unit components, parts replacement (planned or required by the results of A- and B-inspections) and restoration of components are performed.
The importance of scheduled replacements of turbine components should be noted. If a component has exhausted its service lifetime then it should be replaced even if it has no visible damage. This is due to the fact that it is currently impossible to accurately calculate failure-free operating hours for key components. Mathematical models used in these calculations involve a significant number of tolerances.
Unfortunately, not all companies that operate gas turbine equipment comply with the manufacturers' requirements. From time to time it leads to significant financial losses caused by the failures of gas turbine units.
Our specialists are ready to carry out the full scope of inspection activities for turbine units of various types and manufacturers. Working together with our company is a guarantee of safe and continuous operation of your equipment.