A Comparison of Oil and Gas Lubrication Systems for Closed-Loop Gas-Turbine Machinery Free

Most gas turbines in service today have oil-lubricated bearings. However, when these machines are utilized in closed-loop applications (where the cycle gas is continuously recirculated), means must be provided to insure that the lube oil cannot leak into the cycle gas. The criticality of this problem has led, in some instances, to complete elimination of the problem by use of process-fluid lubrication wherein cycle gas is used as the bearings lubricant. This paper describes design and operational experience with both oil-lubricated and gas-lubricated closed-loop gas-turbine machinery. Comparison of the two lubrication concepts reveals the inherent potential advantages of gas lubrication in terms of system simplicity and reliability.