Recycle Gas Compressor Designed For High Unbalance Tolerance And Stability.

Abstract

A process recycle gas compressor was needed that would be highly reliable and tolerant of suction contaminants of sticky material that is abrasive and corrosive. Squeeze film dampers, pinched diffusers, and other technologies created a robust design that proved highly tolerant of extreme process upsets as well as normal demands. Impeller tip speed limits help control erosion and an open-faced, radial vane impeller minimizes fouling. Custom five-axis milled Inconel 625 impellers with splitter vanes and pinched diffusers allowed adaptation of a standard compressor frame to meet thermodynamic needs without excess flow. Squeeze film damper bearings with flexible pivots yielded a rotor bearing system highly tolerant of unbalance with excellent cross-couple stability. The compressor was test run four hours with a shaking force two and one half times rotor weight while running below vibration and bearing temperature interlocks. Other features were also provided to improve reliability. During two extreme process upsets, the impeller blade tips were almost completely eroded away in just 10 days, but operation was able to continue until a scheduled outage.