Offline compressor washing - where time is really spent

While offline compressor washing is essential, it’s important to make it as quick and efficient as possible without compromising on cleanliness.

So, what actually happens during the wash process? What takes up the most time and are there ways to speed it up? While most people assume the wash stage dominates the outage time, in fact it’s the rinsing and procedural requirements that consume the majority of the time. Let’s dig a little deeper…

Typical outage planning

Good gas turbine management allows outage time for compressor offline washing. Usually, sites plan approximately one shift for an offline wash. However, the actual duration of the wash varies considerably depending on the rinse requirements.

Wash vs rinse time distribution

If you think of compressor washing as having two basic stages: washing and rinsing, you’d be forgiven for assuming it’s the wash stage that takes up the majority of the time. However, washing is typically quick relative to the total outage time and often completed in multiple injection pulses.

Conversely, the rinse phase can become the largest time component in offline compressor washing. As conductivity targets and full foam removal are so important, the rinsing stage of the process must be thorough and complete before the compressor can be considered ready to get back to work.

OEM flow rate differences and procedural impact

Establishing that rinsing accounts for the majority of necessary downtime, next we can look at why rinsing takes so long and steps we can take to cut the time.

One of the factors is offline flow rate, e.g.:

Your rinse efficiency is limited by your turbine’s offline flow rate. In this example, the GE 7FA’s higher offline flow rate enables faster rinsing.

Another limiting factor is procedural differences. We would always advocate following OEM recommendations, and Siemens and General Electric (GE) procedures often specify rinsing until clear or conductivity is achieved. For example, some OEM procedures specify around 29 rinse pulses, often with additional cycles required to reach conductivity targets. This will dictate when you may consider a rinse stage complete and will vary between makes/models of gas turbines.

Detergent choice

An obvious variable to look at is the amount of foam produced during a wash. Foam is a necessary part of effective washing for several reasons including effective blade coverage and contact time. However, excessive foam is superfluous and merely increases rinse time and effluent. Getting the balance right when it comes to foam generation is down to the correct wash chemical choice and accurate dilution. (You can read more about foam in this article.)

We’ve seen reported ranges in offline compressor wash time when using traditional detergents of 12+ hours, and sometimes up to 16-20 hours. In some cases, this can be reduced to approximately 1.5-2 hours with a low foam detergent, often with just 15-20 rinse pulses while achieving desired cleanliness. We don’t need to explain the difference to productivity this time saving could make to your operations!  

While that’s an extreme example, customers often report their observed outage reduces by 2-3 hours and sometimes 5-10 hours by switching to FYREWASH®.

Faster rinse → faster return to operation → revenue protection

Water as a limiting factor

Some gas turbine sites face the added obstacle of a limited water supply, which complicates the wash/rinse process. In some cases, water usage can exceed 3,000 gallons per wash, and significantly more when high-foam detergents are used. Most plants have demineralised water systems (recommended) but challenges occur at:

• Remote pipeline stations
• Older facilities
• Sites without large water capacity

Limited available demineralised water can extend outage time and again highlights the benefits of selecting a detergent which produces the necessary foam without excess.

Operator behaviour insights

In the real world, operators will tweak processes depending on their unique situation. Regardless of OEM recommendations/guidelines on how long a wash will take, there is inevitable variation between sites, and water availability is a significant limiting factor.

Operators must wait to achieve conductivity targets, and some report double-diluting detergent in order to cut down on the foam produced. However, while this will reduce foam, it also means the wash will be less effective, and the compressor/productivity will suffer in the long run.

How to reduce offline compressor wash time

Offline compressor washing is about so much more than the wash step itself. Time is spent on:

• Setup and preparation
• Wash cycles
• Rinse cycles
• Conductivity verification
• Water handling

If you’re looking for ways to reduce your downtime spent on washing, instead of double-diluting detergent, we would recommend looking at your detergent choices and finding the one most appropriate for your site and situation. Getting the balance right between cleaning efficacy and foam production is essential.

Utilising wash skids effectively can also cut down on procedural steps and save valuable time while ensuring the most effective wash possible.

Get in touch

At Rochem, we have specialised in gas turbine compressor washing for over 40 years. Based on our industry experience, we believe rinse efficiency may be the most underestimated variable in compressor maintenance, and we can help you address this at your site.

Our range of products is designed to achieve exceptional results as efficiently as possible. From bespoke wash nozzles and our range of industry-leading FYREWASH® chemicals through to wash skids that simplify the whole process and support from our global team of experts, we are here to help you maximise efficiency through cleaning. Whether you are looking to cut down the rinse time during offline washes or want to address another aspect of your cleaning regime, please get in touch to find out how we can help.