A nuclear power plant needed help identifying the source of sudden vibration step changes of a cyclic nature from a feedwater pump.  This vibration issue only occurred on one of the two proximity probes, which led to MSI being called for assistance.

steam-turbine-driven-feedwater-pump-1024x764

  • Problem Statement (Challenge)
    • What (type of machine): Single Stage, Double Suction, Turbine Driven, Centrifugal Pump
    • Where (State/ Country): Louisiana
    • Why (problem/reason): A nuclear power plant needed help identifying the source of sudden vibration step changes of a cyclic nature from a feedwater pump. This vibration issue only occurred on one of the two proximity probes, which led to MSI being called for assistance.  Additionally, a speed pick up probe’s signal was lost temporarily.
  • Work Performed
  • Results/ Solution
    • Findings: Review of the plant provided data along with the data collected by MSI in the field led to the conclusion that potential magnetism of the rotor system was to blame. The vibration levels measured on the turbine and pump bearing housing were low and acceptable for this style of machine.  ODS testing indicated a minor soft foot phenomenon, but its impact on the rotor vibration issue in question was not related.
    • Impact: The findings led to MSI recommending the inspection of the turbine grounding system.  Voltage, amperage, and a visual inspection of the riding brush mechanism were to be collected and analyzed.  A comparison between residual magnetism on both operating pumps was recommended to see if a difference was present.  Most importantly, the findings led to the increase in the vibration set point to compensate for the elevated vibration levels which were predicted as a result of the residual magnetism.  This allowed the plant to avoid a down power (huge loss in profit) and stay online until the next outage, when further investigation would take place.

double-suction-single-stage-pump-cross-section-300x230
                                                                                             Pump cross section


pump-and-turbine-vibration-trend-plot-300x139
                                                                                    Plot showing reason MSI was called.

                                                                           feewater-pump-orbit-plots-300x220

                                                                                                  Feedwater pump orbit plots  

                                                                              steam-turbine-driven-double-suction-single-stage-centrifugal-pump-MEscope-ODS-model-300x220                                                                                                ODS data points and model

steam-turbine-driven-double-suction-single-stage-feedwater-pump-300x197

                                                                            steam-turbine-driven-double-suction-single-stage-feedwater-pump-300x197                                                                                                          Click image to animate

REAL-WORLD EXAMPLES AND CASE STUDIES

MSI In Action

Case Study

A Cure for the Common Cold – in Turbines

A steam turbine at a waste-to-energy facility in the Northeast underwent a scheduled repair, at which time the turbine bearings were reworked, after which the turbine periodically experienced very high amplitude shaft vibrations.

Case Study

BFP Fluid Drive Troubleshooting

A boiler feed pump (BFP) driven off of the main steam turbine via a fluid drive was experiencing high vibration levels leading to frequent replacement of the fluid drive bearings.

Case Study

Aeroderivative Gas Turbine Modifications to Solve a Problem

MSI was contracted to understand and help solve a high vibration problem on an aero-derivative gas turbine driven generator.