Why doesn’t my compressor recover full performance after washing?

One of the reasons gas turbine operators clean their compressors is to regain lost performance. However, their equipment sometimes recovers less than they’d expected.

Today we’re looking at the reasons gas turbine compressors may not be restored to full performance following washing, helping you understand and tackle this potential issue at your site. 

Why would gas turbine compressor washing restore lost performance?

Foulants accumulate within the gas turbine compressor during normal use, adhering to blade surfaces, reducing the volume of the compressor, impeding optimal airflow and damaging delicate components through erosion and corrosion.

By washing these foulants away, it’s logical to presume lost performance will be regained, and this is often the case. 

However, there are numerous reasons that not all performance loss can be recovered through washing. We will look at each in turn and discuss how to address them.

Fouling vs damage

Performance loss caused by fouling is generally recoverable through washing (although stubborn deposits may require more attention). The foulants can be removed, and performance should be regained. 

However, performance loss caused by erosion, blade damage, increased clearances or mechanical wear is not recoverable through washing. This physical damage cannot be repaired by washing, so if this is your issue and you’re suffering significant losses, you could consider replacing parts. 

Online and offline washing

Research suggests that different cleaning methods achieve different levels of performance recovery:

• Online washing is primarily used to maintain compressor cleanliness during operation.
• Offline washing generally provides a more thorough clean and greater performance recovery.
• Severe or hardened deposits may require manual cleaning during major maintenance.

A combination of wash types will:

a) keep fouling to a minimum and

b) remove tough deposits in good time. The idea behind cleaning is to prevent foulants from excessively affecting compressor volume/airflow and removing them before they have a chance to erode/corrode surfaces. An effective cleaning schedule should manage this. 

Spray distribution

Cleaning solution can only clean the places it contacts. If your spray distribution is limited/uneven, you have no chance of conducting a thorough clean.

When addressing spray distribution, you should consider:

• Nozzle location
• Spray angle
• Compressor geometry
• Airflow through the compressor

Droplet characteristics

Research suggests that cleaning effectiveness depends on more than simply increasing wash pressure. Droplet size, momentum and penetration all influence how effectively deposits are removed from compressor blades.

Your wash nozzles should be optimised to deliver droplets engineered for the best wetting, coverage and clean possible. 

Water quality

The main (sometimes only) component of wash solution is water. The purity of this water is of great importance when it comes to cleaning, as you want to avoid introducing avoidable foulants and/or leaving residue after a wash and rinse.

Cleaning chemistry

Different operating environments create different contaminant types which generally enter the system via the air inlet (even once filtered).

Depending on your site, your compressor may suffer from foulants including

• Salt contamination
• Industrial pollution
• Hydrocarbons
• Oil aerosols
• Pollen
• Insects
• Dust

You should ensure your chosen cleaning chemicals target relevant foulants.

Alternative causes of performance loss

If you carry out regular washes, are happy with your spray pattern, droplet size, water quality, and everything else already mentioned, there may be another cause of performance loss at your gas turbine site. 

Consider the following as you seek to regain lost power:

• Inlet filter condition
• Turbine degradation
• Combustor condition
• Instrumentation
• Ambient operating conditions

Troubleshooting

If you’re struggling to regain lost power through cleaning, use this summary table to help:

Get in touch

Sometimes gas turbine site operators hope a single wash will regain all lost power in one go, despite years of neglect. Sometimes they are already conducting regular washes and can’t figure out why they’re not getting better results.

The reason(s) for washes not leading to full performance restoration may not always be clear, but hopefully this article has given you some suggestions to consider.

Whether you know exactly what you want to address or not, we’re here to support you.

At Rochem, we’ve specialised in gas turbine compressor cleaning for decades. Our cleaning chemicals and equipment are chosen at thousands of sites around the world, and we’re trusted by customers for our world-class products and customer support.

If you’d like to regain lost power at your gas turbine site and are struggling, we’ll be happy to help. Please get in touch to discuss your requirements.