Inspections and proper turbine support are needed to ensure gas turbines can continue working efficiently and safely. There are many factors that can impact the designated intervals for inspections and these can influence the three primary gas turbine modules, the compressor modules, the turbine module, and the combustion modules, making frequent or less frequent turbine inspections necessary depending on the conditions.
The largest factors that impact turbine support and inspection intervals are the types of operations, including the base and peak loads, as well as the trips and starts. The type of fuels and the quality of air entering the turbine will also impact these intervals.
Peak load can have six times the effect on turbine blades when compared to base load. Likewise, a trip from full load will be the equivalent of 8 starts. While a part load operation at 80% can reduce the inlet temperature by 10%; however, this isn’t sufficient enough to influence inlet pressure until the load gets to around 70%.
The Types of Fuel
Fuels heavy in hydrocarbons release more heat than natural gas. This excess heat can reduce the life of combustion modules and components making frequent turbine support and inspection essential. Furthermore, heavy oils that have corrosive elements can lead to corrosion of the blades and nozzles. Switching to a natural gas fuel source can reduce corrosion problems making inspections of this nature less frequent.
Air that contains particles of oil, dust, and salt can corrode and wear away the compressor modules. These abrasive materials can remove material from the flow path and create detrimental issues. Likewise, fouling, caused by dust becoming caked to the blades, can reduce efficiency and lead to further issues. To prevent this, more frequent turbine support is needed, as well as additional filter cleaning and replacement.
Every turbine manufacturer will provide a schedule by which inspections should be conducted. These inspections typically include a hot gas component inspection, combustor inspection, and major inspection. On average the recommended maintenance intervals are:
Hot gas inspection at 24,000 equivalent operating hours
Combustor inspection at 8,000 equivalent operating hours
Major inspection at between 48,000 and 50,000 equivalent operating hours
It’s important to keep in mind the manufacturer specifics, as well as the unique operating conditions that your turbines are working at. Keeping this in mind and scheduling turbine support inspections at the right times can help you keep your turbines running as efficiently as possible.