Gas Turbine Air Filtration Systems For Offshore Applications

TutorialAir filtration plays a key role in achieving high availability and low maintenance cost for Gas Turbines, in particular in offshore applications. Offshore applications pose a particular challenge, since they have to provide protection both against liquid water ingestion (and the salt particles dissolved in this water), as well as against very small particles (dry salt and other dust). Two fundamentally different concepts have emerged: High velocity systems and low/medium velocity systems, distinguished by the face velocity of the air entering the filter elements. While high velocity systems rely on vanes to remove liquids from the airstream, modern low/medium velocity systems use special filtration materials (usually in the last, high efficiency stage) that prevent water from passing through the element. Older systems did not have this type of filters available. The tutorial will discuss the physical principles of these air filtration concepts. The paper discusses the issues of filtration efficiency, dust holding capacity, as well as the capability to prevent water from entering the gas turbine. The discussion involves also the change in filtration characteristics over time. For the operator, it is important to understand the impact of the filtration system on engine degradation from fouling or hot corrosion, the frequency of intervention (water washing, change of filters), in conjunction with the operating conditions at site