Performance Deterioration of Intake Air Filters for Gas Turbines in Offshore Installations

Efficient inlet air filtration is a key element for limiting fouling, erosion, and corrosion in the compressor section of offshore gas turbine installations. Current filtration systems are normally successful in preventing serious erosion and corrosion problems in the compressor section, but significant performance deterioration caused by compressor fouling still remains a challenge. This performance deterioration increases fuel consumption and emissions and has a particularly severe economic impact when it reduces oil and gas production. Operating experience from different offshore installations has shown that the deterioration rate in gas turbine performance increases when the turbines are operating in wet or humid weather and that the differential pressure loss over the intake system is affected by ambient humidity. An experimental test rig has been built in the laboratory at the Norwegian University of Science and Technology (NTNU) in order to increase understanding of the fundamentals related to gas turbine inlet air filtration. This paper presents the results from an experimental investigation of the performance of gas turbine inlet air filter elements that have been in operation offshore. Performance under both dry and wet conditions is assessed. Different types of filter elements show significantly different changes in differential pressure signature when exposed to moisture, and all of the tested filter elements demonstrate a loss of accumulated contamination after operating in wet conditions. Hence, contaminants originally accumulated by the filter elements are re-entrained into the airstream on the downstream side of the filters when they are exposed to moisture. The change in differential pressure signature as a result of operating in wet conditions demonstrates another weakness of solely applying differential pressure for condition monitoring of the filter system.