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Analysis: The perils of incorrectly installed filters

by Guest on Dec 18, 2017

Tim Nicholas, gas turbine technical services leader, CLARCOR.
Tim Nicholas, gas turbine technical services leader, CLARCOR.

The impact an inlet filter has on protecting gas turbines and maintaining the efficiency is well known among operators. Filter manufacturers can recommend filtration solutions that will best handle local environmental solutions but even the best filter in the world will not protect a turbine if it is not correctly installed.

Ultimately operators care about how the gas turbine performs and to ensure this is optimised, they need to rely on consistent quality of air entering the machine. Filters are often installed incorrectly and the impact on gas turbine performance is dramatic. What are the common mistakes that are made in filter installation and what should operators look for in terms of turbine and filter performance?

When considering the impact of poor filter technology and incorrect installation, it can be seen that in around six months, output power drops by 8MW as turbine performance degrades. This is due to contaminants entering the system, fouling the turbine blades and reducing aerodynamic efficiency.

This reduction in performance not only directly impacts process efficiency but also indicates the turbine is at risk of more permanent damage. If left in this condition, the installation will have elevated risk of unplanned outages and increased maintenance overheads, which will decrease process availability.

Protecting turbine performance

Modern, correctly installed filtration technology protects turbine performance. While the old technology resulted in immediate decline in turbine output following an offline wash, the months following the new filter installation show turbine output remains flat.

If we were to look at this difference with respect to the financials, the difference is extremely significant. In 4,500 fired hours of operation before/after, a difference of >$400k could be recognised (before – 4,500 hours x 8MW x $30/2 = $540k; after – 4,500 hours x 1MW x $30/2 = $67.5k).

Selecting an appropriate filtration solution to match particular site conditions is critical to protecting turbine performance. One filtration solution cannot meet the needs of all the varying environmental conditions at different turbine installations in locations that have very diverse environmental conditions.

Gas turbines are installed in some of the harshest environments on the planet, ranging from offshore platforms, where salt and sea spray challenge systems, to hot desert locations with high levels of dust and seasonal fogs that can lead to rapid blockage of some filter media types.

Standard filter tests and ratings may show that different models offer very similar performance, but these are based on laboratory conditions and may not reflect how the filter will actually perform once installed. It is imperative to select a good filter option to handle local environmental conditions.

However, ensuring the filter is correctly fitted and managed through its lifetime is just as critical. At the end of the day, the outcome an operator is looking for is based on the performance of the turbine, not the specification of the filter product. Trying to save a few dollars on filters or their installation costs is false economy, and may result in the loss of millions of dollars in some high-value processes due to unplanned outages.

Results of incorrect installation

An installation should be inspected by qualified personnel to ensure the turbine and associated processes are properly protected. The descriptions about the images given  demonstrate few examples of things that can go wrong.

Image 1 shows the results of an incorrectly sealed gasket. If the gasket was sealed correctly, the inside area would be clean and white. Instead, dust and dirt can clearly be seen throughout the installation. This will impact turbine performance, increase maintenance and may result in permanent damage to the turbine.

It is widely accepted and proven that how a filter is performing will impact the output of a turbine. Image 2 shows a filter with brittle glue and Image 3 displays a filter that has corroded. Both of these have been installed for too long. Contaminants can bypass damaged filters, leaving the turbine unprotected.

Glue or corroded mesh from the filter can also become detached and ingested by the compressor. This has the potential to cause sudden and major damage to the turbine internals. Knowing how important it is to maintain air inlet quality for turbine performance, it makes no sense to leave filters installed beyond their recommended life.

Regular inspection by qualified personnel is important to ensure any issues within the inlet house are identified and rectified. Image 4 shows the result of a valve failure which led to filters not being cleaned. It can be seen that the filters have become clogged and the result was a considerable increase in differential pressure, which significantly reduced turbine performance. If filters eventually become completely blocked, air cannot reach the turbine and this will result in an unplanned outage.

Significance for filtration experts

There are many aspects of an installation to consider when selecting a filtration solution that will best protect a gas turbine and help deliver on operational goals and targets. Although a relatively small part of an overall installation’s cost, a filter can have huge impact on the performance and reliability of a turbine. Incorrectly installed or improperly maintained filters present a huge risk to an operation and, especially in high value processes, could result in the loss of millions of dollars.

Any mechanical team can install filters but if they are not experienced or do not have sufficient expertise in this area, mistakes can be made. The importance of a filter to a plant’s performance means they should not be treated as a commodity. Filtration experts offer a range of services to ensure filters are correctly installed and continue to protect machinery throughout their lifetime.

This includes qualified personnel to manage and inspect installations, yearly inspection services and predictive maintenance. A proactive approach to filter maintenance is highly recommended as this can increase process availability, reduce risks to operations and offer excellent return on investment.


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