NEWS RELEASE                                                                                        October 2019

True Cost of Gas Turbine Inlet Filters

The McIlvaine Company is working with associations, media and suppliers to create true cost analyses of combust, flow and treat products and services. One such initiative is the “True Cost of Gas Turbine Inlet Filters”.

The true cost of a gas turbine inlet filter can be affected by a large number of factors. These factors are not constants but are changing. The filter purchaser is challenged to not only identify these factors but to keep up with the changes.

Large gas turbines are used to generate electricity by utilities. Smaller gas turbines drive pumps and compressors in locations with extreme conditions such as desert dust, artic snow or sea spray on an oil rig. As turbines have become more efficient, they have become more susceptible to damage from contaminants in the combustion air.  This ambient air from the surrounding environment can contain high dust loads.  In California with very tight emission standards the particulate in the  inlet air to the turbine can exceed emission limits. Thus the gas turbine has to act as an air cleaning device.

The challenge for  gas turbine inlet fiber, media, and filter suppliers is to increase gas turbine availability in all environments with newer and more sensitive gas turbines. The newer turbine designs are negatively impacted by small particles.  This has led to the use of HEPA filters with efficiencies classed as H10/E10 and higher.  Studies show that turbine maintenance can be reduced with even higher efficiency E12-U17. One study showed that even if the cost of higher efficiency filtration were four times higher than lower efficiency filters, the true cost would be lower.

One can choose a system with non-cleanable filters. They are relatively inexpensive but require continuous filter replacement.  By using a sequence of inefficient but inexpensive pre filters and a final high efficiency filter, the replacement cost can be minimized.

An alternative is to use a cleanable filter. Periodic air pulsing knocks off accumulated dust.  These systems are available from many suppliers if the F-9 efficiency is all that is desired.  Cleanable filters with H12 efficiency are available from only a few suppliers.  On the other hand there are many new developments which will expand the number of choices.

In terms of high efficiency dust capture mechanisms there is a choice between wet laid glass and synthetic nanofiber non-woven laminates or membranes. The traditional glass media for HEPA filtration has been used primarily in non-cleanable filters.

Quantifying the benefit is a balance between reduced fouling and increased pressure drop. The increased pressure drop can be estimated to restrict performance by approximately 0.4%, while cutting fouling provides a 1.2% improvement in output (empirical average). Therefore, the overall result is a potential efficiency improvement of 0.8%.

Alliance Pipeline believes that the E12 filters from Gore may allow Alliance to extend the interval between overhauls of its aero engines from 25,000 to as many as 50,000 hours (from three to six years).

The many factors and media choices impacting gas turbine inlet filter selection  have been discussed in a background document on display at

In the past the most efficient filters which were used on gas turbine inlets were rated F-9 with efficiency of more than 95% on particles 0.4 um diameter.  The most penetrating particle size is about 0.2 um where the efficiency is much lower.  Higher efficiency filters are rated based on the most penetrating particle size as follows.

HEPA Class

Retention (total)


> 85%


> 95%


> 99.5%


> 99.95%


> 99.995%


> 99.9995%


> 99.99995%


> 99.999995%

Membrane laminates such as used for dust collection can meet efficiencies up to E12.  The question is whether this is sufficient?

There are a number of new filter and media designs which need to be evaluated.  Mann & Hummel Vokes introduced the Aircube Pro Power S which utilizes a new synthetic base media with much higher resistance to mechanical stress than glass fiber media and a stable high efficiency during operation. It is water and salt repellent while being extremely robust.

DHA filter has introduced a cleanable HEPA filter for gas turbine inlets which it will be displaying at PowerGen

The Guide to True Cost of Gas Turbine Inlet Filters will be used to facilitate discussions at a number of events in the coming months. It will be used along with a tour guide on the subject at the  PowerGen exhibition in November.

It will also be the subject of a discussion at FiltXPO which will be held in Chicago in February.

The Decision Guide is continually updated and included Gas Turbine and Reciprocating Engines  Decisions  It is free of charge to gas turbine and engine owners and funded through supplier subscriptions.

To participate in the True Cost of Gas Turbine Intake Filters contact Bob Mcilvaine at This email address is being protected from spambots. You need JavaScript enabled to view it.  direct 847 784 0013 cell 847 226 2391.