Train Torsional Vibrations: Monitoring System Based on Model Result

Development of a novel train torsional vibration monitoring approach utilizing system modal analysis has been reported in this paper. Common use of high power electric helper machines especially in large turbocompressor strings together with LCI speed control system characteristics dramatically increase the risk of machinery torsional vibration problems. Contemporary, industry-wide accepted measurement technologies (strain gage with telemetry, optical probes, laser) fit well the test needs but their lack of ruggedness and durability as well as problematic installation impacting machine operation don’t allow to consider them for the long-term monitoring applications. The authors present a methodology which allows to evaluate alternating torque amplitudes in different string sections based on standard instrumentation installed on a train. The approach adopted in this paper relies heavily on modal representation of dynamic system, being analyzed. Described calculation method utilizes results of such analysis along with gas turbine speed pick-up signal spectrum. Robustness and accuracy of the proposed technique was benchmarked against test data coming from several LNG production train measurement campaigns, where the alternating torque was measured by means of standard measurement systems. Authors present the results of such verification together with prospective system applications.