Has Your Compressor Cleaning Strategy Kept Up With Changing Turbine Duty?

The operating profile of gas turbines changes over time. Small tweaks to practises over the weeks, months and years add up to a duty profile unrecognisable from how the turbine started out.

Often, cleaning strategies are left lagging behind; a schedule that was set up for the gas turbine’s original working pattern remains unchanged and no longer suitable. This can have a big impact on productivity and equipment lifespan without you even realising.

So, here’s the question: is it time to review your gas turbine cleaning strategy?

Why is gas turbine duty changing?

The way we generate electricity has changed a lot in recent years and the way we use gas turbines today is not the same as they were run when their maintenance programmes were originally set up.

With increasing wind and solar power generation, the habitual use of gas turbines has dropped. However, when there is insufficient wind or sun to meet demand, gas turbines are fired up to fill in the gaps. This has led to a more ad hoc use: more starting and stopping and a very different profile of use beyond those foreseen under the classic base-load or cyclic operations.

Existing inspection intervals were likely put in place on the assumption that the gas turbine will predominantly run at base load. If that is no longer the case, it’s important to review these intervals and make any necessary changes to maintenance practice.

Demand for gas-fired power is high

With the emphasis on renewable power, it might be surprising that there is relatively high demand for new gas turbines. Demand currently outstrips supply, and there is at least a five-year waiting time from order to delivery of large gas turbines. This means many older turbines are still in use, often sticking to outdated cleaning schedules.

Are gas turbines used more or less than before?

The age of the gas turbine can impact how its usage has changed. US Energy Information Administration data suggests newer, more efficient plants are run more, with combined-cycle plants at an average capacity factor of 64%. Meanwhile, those built in the 1990s average 35%, running less often/more flexibly.

Whether your gas turbine now operates more or less often, under higher or lower loads, has the cleaning schedule kept up? If you haven’t reviewed your strategy for a while, it’s a good idea to think about it now.

Does cycling or peaking cause more compressor fouling?

After acknowledging your turbine’s duty programme has changed since implementing your current cleaning schedule, you’ll likely be wondering whether cycling or peaking causes more compressor fouling. We’re not here to categorically say whether one is ‘worse’ than the other, as there isn’t enough evidence to guide us. The simple rule is: if your duty has changed, you should review your cleaning strategy.

What we do know is that fouling levels are heavily influenced by airborne deposits and a variety of factors include:

• Location and surrounding environment
• Airborne contaminants
• Inlet filtration
• Humidity and weather
• Compressor design
• Operating conditions
• Existing contamination
• How the compressor is cleaned

How do you know it’s time to review your cleaning strategy?

It can be tricky to know when to review your cleaning strategy, which is why they go unchanged for years, sometimes decades. If the turbine appears to be working fine, it’s tempting to leave things as they are.

However, if you take a closer look, your gas turbine may be giving you telltale signs that it needs a clean. Signs such as a gradual reduction in power output and higher exhaust heat may go unnoticed but could indicate fouling and associated loss of efficiency. This article goes into detail about the signs you can look for.

Another good way to determine if your cleaning strategy should be reviewed is to answer these questions:

• Has the turbine’s duty changed since the cleaning schedule was implemented?
• Are starts and stops more frequent, or is the unit running longer between shutdowns?
• Is the turbine spending longer periods offline?
• Is it running at different loads?
• Have seasonal or ambient conditions changed?
• Has the rate of compressor performance loss changed?
• Is the current cleaning interval simply based on how things have always been done?

If the answer is “yes” to any of the above, you should check that your cleaning programme is still suitable and make adjustments if necessary.

Calendar-based or condition-based cleaning?

Deciding on a new cleaning schedule can feel daunting. Perhaps the biggest question is whether you should clean at regular, scheduled intervals (calendar-based) or at a time determined by the condition of the gas turbine compressor.

Calendar-based

Washing after a set period or number of operating hours might be what’s specified in your OEM requirements, and that should be followed. This method is a good rule of thumb and starting point to ensure a level of cleanliness.

Condition-based

Using performance and condition to help decide when a wash is necessary/worthwhile. This approach can be helpful in particularly harsh environments when foulants may accumulate faster than OEMs may expect.

A regular pattern of on-line and off-line washing is sensible as it ensures the cleans are completed. It’s a good starting point but it’s useful to keep collecting and monitoring performance data. The art is finding the right balance, and the timings for one turbine will be different for another. Plus, when there are changes to how a turbine runs, the schedule should be reviewed.

Where does off-line washing fit in a flexible operating strategy?

Regular on-line washes are extremely useful for keeping foulants to a minimum. However, off-line washes, which give cleaning chemicals more contact-time, are also important for removing stubborn build-up. Read more about the differences between on and off-line washes here.

Encouragingly, Meher-Homji and Bromley state that when performed correctly, off-line washing “will typically restore virtually 100 percent of the lost power and efficiency attributed to compressor fouling.”

If your gas turbine now has more periods of downtime, these could be useful opportunities for off-line washes. Are you making the most of them?

On the other hand, if your turbine is running harder with fewer shutdowns, are you neglecting off-line washing to the detriment of your equipment?

It’s time to look at how your turbine currently runs, not how it ran when your cleaning schedule was devised, and ensure it considers:

• The gas turbine compressor’s condition
• The plant’s schedule

Keep OEMs in mind regarding off-line washing procedures, including cool-down requirements before washing.

Why location and season matter

When you think about it, turbine location and even the time of year inevitably have a huge impact on compressor cleanliness. As most foulants are introduced via the air, variables such as pollen and humidity not only play a huge role in fouling levels, but also vary site-to-site, season-to-season.

Take a look back at your site’s historical performance for the best guide to fouling levels and their fluctuations. Do seasonal patterns affect cleanliness at your site? Could a tweak to your cleaning schedule address this?

Summary checklist: what to review when your turbine’s duty changes

Whether your turbine’s duty changed years ago or much more recently, if you haven’t reviewed your cleaning strategy since before the change, it’s time to take a look.

This useful checklist helps you decide if you need to review:

• Has your turbine’s operating profile changed?
• Has the rate of compressor performance loss changed?
• Are you monitoring compressor performance consistently, and correcting for ambient conditions?
• Does your offline washing programme still reflect how the turbine runs today and the compressor’s actual condition?
• Are you making use of planned stops for offline washing?
• Is your wash equipment working correctly?
• Are the nozzles and wash delivery giving good blade coverage?
• Is the cleaning chemical suited to the contamination present?
• Is the wash solution being mixed at the right strength, rather than over-diluted to reduce foam?
• Is the wash being given enough soak time before rinsing?
• Are you following current OEM recommendations?
• Are you checking the results after each wash to see whether the programme is working?

Conclusion

Compressor cleaning works best as a programme, not a one-off maintenance task. Operating profile, environment, compressor condition, wash equipment, chemistry and wash timing all affect the result. With so many variables, it’s important to review your cleaning programme when something changes to ensure you’re still getting the most out of your washes.

If you’re ready to review your cleaning programme and have any questions, please get in touch. We specialise in cleaning equipment and chemicals for gas turbine compressors and are here to help tailor a strategy optimised for your site.

References

1. Farhat, H. and Salvini, C. (2022). New lifing criterion for land-based gas turbines in flexible operation mode. Energy Reports, 8. Open access:https://www.sciencedirect.com/science/article/pii/S2352484722000610 [Accessed 6/10/26]
2. Noble, B. (EPRI), writing in Utility Dive: 5-year waits and rising costs: How demand is redefining the gas turbine market: https://www.utilitydive.com/news/5-year-waits-and-rising-costs-how-demand-is-redefining-the-gas-turbine-mar/813385/ [Accessed 6/10/26]
3. US Energy Information Administration (November 2023): Natural gas combined-cycle power plants increased utilisation with improved technology: https://www.eia.gov/todayinEnergy/detail.php?id=60984 [Accessed 6/10/26]
4. Meher-Homji, C.B., Chaker, M.A. and Motiwala, H.M. (2001). Gas Turbine Performance Deterioration. Texas A&M Turbomachinery Symposium. Full paper: https://oaktrust.library.tamu.edu/handle/1969.1/163330. Use for: recoverable versus non-recoverable deterioration and performance monitoring. [Accessed 6/10/26]