This page explains the main inspection types and what drives their timing.
The three main inspection levels
A combustion inspection covers the fuel nozzles, liners, transition pieces and related parts that wear fastest. A hot gas path inspection goes further, opening the turbine section to inspect and replace nozzles and buckets or blades exposed to the highest temperatures. A major inspection opens the whole machine, including the compressor, and is the longest and most expensive outage.
Aeroderivative turbines follow a similar logic but often swap the whole gas generator for a refurbished one, which shortens the site outage.
Hours, starts and trips
Manufacturers set intervals in fired hours, in starts, or in a combination of both, with factors for trips and fast starts. A turbine running baseload accumulates hours; a peaking unit accumulates starts. Each trip from full load counts as several normal starts because of the thermal stress.
That is why the same model can need inspections at very different calendar intervals depending on how it is run.
How duty and fuel change the picture
Running on liquid fuel, peak firing, water or steam injection and poor inlet filtration can all shorten intervals. Dirty air erodes the compressor; contaminated fuel attacks hot section parts. Good filtration, fuel quality control and avoiding unnecessary trips extend the life of components.
Our page on inlet air filtration explains how cleaner air protects the compressor.
Planning outages and spares
Inspections need parts on site before the outage starts: combustion hardware, hot gas path sets, seals and consumables. Many owners keep a rotable set of hot section parts that is refurbished between outages. Outage planning also covers cranes, specialist tools, inspectors and accommodation for the crew.
Plants with several units stagger their inspections so that firm capacity is maintained.
Using inspection intervals to compare turbines
When comparing turbines for a project, look at the interval structure as well as the price. A turbine with longer intervals, or one that allows module exchange instead of long site outages, can deliver more energy over its life. The cost of parts at each inspection, and whether they can be refurbished rather than replaced, also shapes long-term value.
A simple model that combines the expected operating profile with the inspection pattern shows how many outages each option will need over the project life, how long they will last and what they will cost.
Records and remaining life
Accurate records of hours, starts, trips and parts history are essential, both for maintenance planning and for resale value. When a used or remanufactured turbine is offered, these records show how much life remains before the next inspection. USP&E’s remanufactured GE Frame 6B units, for example, are refurbished to zero hours.
Our gas turbine operations and maintenance page explains how we run turbines between inspections.
About USP&E
USP&E installs, operates and maintains gas turbine plants as an EPC and O&M contractor, not a broker, with 150+ power projects in 45+ countries, 25,000 MW contracted since 2002 and 24+ years in the field. Our turbine O&M services include outage planning and inspection management.
Offices: Colorado Springs (1755 Telstar Dr, Suite 300), Knoxville (800 S Gay St, Suite 700), London (162-168 Regent Street), Johannesburg (22 Kildoon Rd, Bryanston), Cape Town (31 Brickfield Road, Woodstock) and China (No. 1 Ningzhou Road, Wuxi). Regions: USA | AFRICA | UK | UAE | CHINA. ISO 9001 and ISO 45001 certified.
Questions about gas turbine inspections
What is a hot gas path inspection?
An inspection that opens the turbine section to check and replace the nozzles and blades exposed to the highest temperatures.
How often does a gas turbine need a major inspection?
It depends on the model, fired hours, starts and trips. The manufacturer sets the interval, and duty changes it in practice.
Do starts or hours matter more?
Both. Baseload units are driven by hours, peaking units by starts, and trips count as extra starts.
Why do inspection records matter when buying a turbine?
They show how much life remains before the next inspection and therefore how soon major costs will arise.
Planning your next turbine outage?
Share the unit history and operating profile, and we will help plan the inspection scope, parts and outage schedule.
For a first conversation, use the turbine service contact page, ring +27 10 822 2324 or send the details to info@uspeglobal.com. Turbines and parts available now are in the natural gas turbine inventory.