Proactive shop strategy for a successful turbine-generator rotor outage

摘要

Standard power generation industry practices of inspection, machining, balancing, assembly and alignment have been developed by OEMs for newly manufactured rotors, and implicitly assume that rotors are within ideal dimensional specifications. However, applying these standard practices in the service industry can fall short for rotors with eccentricities outside such specifications, and by design do not catch the errors that cause true dynamic problems, because they are assumed not to exist, or their effects are unrecognized by traditional industry practice with regard to real rotordynamic behavior. This misunderstanding leads to costly problems, like reinstalling a "balanced" rotor from the shop only to experience high vibrations upon installation, often followed by days or weeks of lost production while field balancing in an effort to salvage the situation. A "successful" start up following a planned outage means that there will be no need for field balancing following the restart of the unit. Since most causes of dynamic problems on turbine-generator rotors are present (in the form of rotor and coupling eccentricities) even prior to starting the unit, almost any such problem can also be identified and fully prevented during the outage if only a few key, improved steps of measurement and analysis and the proper balancing method are included into an outage scope. Specifically, this must include collection and evaluation of total indicator runout (TIR) readings to identify any coupling defects and any excessive rotor bow or distributed eccentricity, and utilization of a new balancing method (using 2N+1) planes if the rotor body exceeds runout limits of ～0.002" eccentricity.