Processing Magazine

Filtration solution leads to three years between shutdowns

Pre-filters can be changed out while turbine engines continue running

March 1, 2014

By Frank Schollmeier

A primary goal of many a plant manager is maintaining continuous and cost-effective operation of a plant’s turbine engines. When considering this goal, it is important for plant managers to be aware of recent advances in filter designs for turbine air intakes. The latest-generation filters allow longer waits between filter replacements, while improving energy efficiency and reducing CO2 emissions.

Traditional folding, pleated-style cartridge filters have shorter life-spans, consistently lower MERV (Minimum Efficiency Reporting Value) ratings, less surface-area and higher resistance to airflow, resulting in decreased energy efficiency. With many plants using hundreds of these filters at a time, these drawbacks together can impact plant output.

While filtration is vital to efficiency, many continue using outdated lower-grade filters. Over a product lifecycle, these filters cost more and need be replaced more than their more modern counterparts. Shutting down turbines to replace filters is a further waste of plant resources.

A turbine engine must be completely shut down to replace its intake filters. Replacing 100 filters “costs” as much as $40,000. As a result, turbines are only shut down every 12 to 18 months. During shutdown, other critical maintenance and upgrades also often are performed to take advantage of the rare occurrence.

Lifespan is key

Valin Corp., San Jose, Calif., is a technical solutions provider for the technology, energy, life sciences, natural resources and transportation industries.

To reduce plant shutdowns in one of its northern California cogeneration plants, Valin Corp. installed turbine pre-filters made by Louisville, Ky.-based Koch Filter Corp., which can be changed while the turbines continue running. This allows continuous operation for up to three years without a single shutdown, saving thousands of dollars in extra costs and simultaneously increasing energy efficiency and reducing CO2 emissions.

Improved operations were achieved by replacing the turbines’ pre-filters and final filters such that, while initially they may cost as much as 30% more than standard filters, yet over the course of time they deliver better lifecycle value.

While standard final filters require replacement every 18 months, Koch DuraMax 4V High Efficiency Minipleat filters can last three years. Pre-filters are replaced every nine months, but without shutdown. This allows the plant to go twice as long without turning its turbines off, spend less on filter replacement costs and save money it otherwise would have lost during shutdowns.

After upgrading its turbine intake filters, the plant not only found that the higher-efficiency filters reduced shutdown time and saved money; they also decreased plant annual energy costs and reduced CO2 emissions.

The filter’s V-style design allows for a larger surface area on the filter interior, resulting in a low resistance to airflow. This decrease in air resistance reduced the annual energy cost of the filters by 12%. Additionally, the decreased energy consumption created a corresponding reduction of CO2 emissions, diminishing the previous year’s output of 908,553 pounds by 11.4% to 804,719 pounds.

The numbers speak

Prior to converting to the upgraded filters, the cogeneration plant was using a standard MERV 8 rated pre filter with a 30 to 35% efficiency rating for 1.0 to 3.0 micron particle sizes. These filters were replaced with MERV 11 rated Koch Multi-Pleat GT Panel pre filters, which have a 60 to 65% efficiency rating for the same particle sizes. Improving the efficiency of the pre filters allowed the final filters of the plant to run twice as long as previously.

To compare numbers, the final filters the plant was using prior to the switch cost $75 apiece, so after purchasing the required 180 filters, the cost was $13,500. The newer Koch filters were $110.10 each, costing the plant a total of $18,234 for 180 items. The original pre filters cost $8.80 each, totaling $1,584 for all 180, and the new Koch GT filter they were replaced with cost $11.35 each, totaling $2,043 to replace all 180 filters.

While initial investment for the higher-efficiency filters was higher, the plant saved in the long term by having to replace the final filters on a far less frequent basis. The plant was changing out the original final filters and pre filters every 12 to 18 months, which added up to a cost of $30,168 over a 24- to 36-month period.

After switching to the Koch high-efficiency filters, the plant was able to operate continuously for a 24- to 36-month period while only spending $18,234 on a one-time filter replacement. In addition, the new Koch Multi-Pleat GT Panel pre filters needed to be changed out every nine months, which cost $8,172 over a 24- to 36-month period. However, the plant was able to keep its turbines running for that entire amount of time, saving money it would have lost by shutting down to replace the final filters. After all was said and done, Valin had saved the plant $11,095 annually, or 16 percent of their entire filter costs.

Frank Schollmeier is the northern California industrial sales manager for Valin Corp. (

Koch Filter Corp. ( manufactures a wide range of filters for gas turbine air intakes of all sizes and types. Koch products are presently installed in nearly every imaginable environment, from hot and gritty desert environments to salty coastal locations to icy arctic applications.