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MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Introduction to MPS and Monitoring of Shaft Voltage and Shaft Grounding Current in Rotating Machinery By Paul Nippes, P. E. and Beth Galano Magnetic Products and Services, 2135 Highway 35, Holmdel, NJ Copyright 2007 Magnetic Products and Services 07733 USA www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” • • Founder and President, Mr. Paul Nippes, P.E. has been consulting to Petrochemical, Power Utilities and Industry since 1965. • IEEE C50 Chairman for many years, Cigre, ASNT and ASTM Contributor. • A Motor and Generator designer with Allis Chalmers and Elliott Company, Electro Dynamic Division of General Dynamics, a Penn State Graduate and a Professor at the University of Wisconsin. In Paul’s Electrical Engineering consulting capacity, due to the frequency of “bearing failures” in his consulting practice, Mr. Nippes championed this research and developed products to provide solutions. Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” • Areas of specialization… 9 Magnetism and the problems it can cause in Rotating Machinery, Industrial Processes, or in any application. 9 Shaft Condition Monitoring - CBM using Stray Shaft Currents and Shaft Voltages in Rotating Machinery for Early Warning of Developing Faults. 9 Field Services – Degaussing, Magnetizing and Shaft Voltage Testing Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” SHAFT CURRENT FROSTING Shaft Journal Bearing Pad Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” SHAFT CURRENT EFFECTS Spark tracks Copyright 2007 Magnetic Products and Services Gear Pitting www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Electric Current Erosion of Thrust Bearing Pads from a Turbine Driven Natural Gas Compressor Spark Tracks on the Active Pad Face Pad Steel Backing Erosion on Two Adjacent Pads Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Spark tracks Developing into Heavy Current Discharge Melting into the Babbitt Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Degaussing Turbine Diaphragms Degaussing Blower Casing Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Demagnetizing Screw Compressor Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Auto Degauss Auto “Down-Cycle” Demagnetizing is Systematic Removal of Magnetism Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Measuring Magnetism MPS Gaussometer Avoid Field Indicators (Magnetometer) Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Red – No Weld, Yellow – Maybe?, Green – Good to Weld Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” South China Sea On Barge Vertical Pipe Welding Magnetic Field Stabilization Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Portable Magnetic Particle Inspections Applied to Military Impellors Procedures Developed by an ASNT Level III (MPS Customer) Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Military Applications – Degaussing Solutions Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Shaft Voltage Surveys Grounding Brush Performance Checks Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Failure Analysis and Solution Recommendations Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Carbon brush contact surface comparison Normal Glazed Figure #4 Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” 1. Ground the Shaft 2. Check Grounding Devices Often via Local or Remote Monitoring Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Grounding Brush Reliability is Critical Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” SHAFT CONDITION MONITORING (SCM) a Patented Technology A continuous monitoring technology that uses shaft current and voltage profiles in operating units for early diagnostics and prognostics to identify developing problems in electrical and non-electrical rotating machinery. Permanent Mount Monitors, Rack Mount, Din-Rail Modules or Sensors = Grounding Brushes Hand-Held Monitors Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” MPS Signal Conditioning VCM-E disposes of numerous and varying frequencies and amplitudes for the purpose of sensing only the important signal changes in waveform fundamental frequency, peaks and averages. At the earliest changes and/or an excess in these quantities, action can be taken to identify and confirm possible problems. Confirmation may include collection and analysis of other unit operating parameters. Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Shaft Grounding And Voltage Sensing Applied To Industrial Class Rotating Machinery Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” GENERATOR HP TURB. IP TURB. LP TURB. EXCITER NO BRUSHES NO MONITORS AND NO PROTECTION Shaft currents are not confined nor controlled. Shaft current damage to bearings and seals is not prevented. Bearing and seal oil films insulate against stray currents. Stray voltages can damage unit or impair efficiency . Events or oil impurities can establish electrical circuits. MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” GENERATOR HP TURB. IP TURB. EXCITER LP TURB. SHAFT GROUNDING BRUSH GROUNDING BRUSH, NO MONITOR, POSSIBLE PROTECTION A quality grounding brush should discharge static electrical charge before damage occurs. A quality grounding brush should establish good shaft contact protecting the nearby bearings. The grounding brush could provide a return path for magnetically-generated current. The brush may require maintenance, with loss of shaft grounding without warning Damage can occur to bearings and/or seals if the generator outboard bearing insulation fails! Shaft current damage to bearings and seals is first indicated by excessive vibration/temperature. MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Shaft Voltage Decrease And Current Increase Indicates Shaft Rub. High Voltage At Sb#1, Inversely Proportional To Steam Temperature Indicates Wet Steam In Turbine. High Current In Grounding Brushes And Low Voltage At Brush Sb#2 Indicates Loss Of Bearing Or Seal Insulation . Rapid Escalation In Both Sb#2 Voltage And Grounding Currents Indicates Developing Stator Winding Fault. Erratic And Pulsing Voltage And Current Indicate Stator Lamination Shorting And Melting . Long Term Gradual Increases In Voltage And Current Indicate Shift In Air Gap. Pulsing, Then Gradual Increase In Shaft Voltage And Current Indicate Rotor Winding Faulting. Shaft Voltage Changes As Excitation Changes May Indicate The Need For A Shaft Voltage Harmonic Filter. Trending Of Each Brush Grounding Current, With Maximum Current Alarm On Each Brush. Each Brush Will Alarm On Low Brush Grounding Current Indicating Brush Or Grounding Maintenance Required. Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Oscilloscope recordings taken from the identical shaft grounding current but with different voltage and time scaling. Upper trace = 112mV @ ~ 70MHz Lower trace = 720mV @ ~ 80Hz Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Erratic grounding on shaft (Voltage source = The blower motor) Ungrounded OB end – similar to IB end OB trace, IB end Ground brush skip Ungrounded IB end – similar to OB end Grounded IB end skip not apparent Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Oscilloscope trace of shaft grounding current composed of a 60Hz fundamental plus a strong common mode bucking third harmonic. Characteristic of magnetic saturation Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Effect on shaft of Electromagnetic Voltages, determined from different resistances in the shaft grounding cable. Ungrounded (40 Volts) 1k Ohm (40 Volts) 100 Ohm (25 Volts) 10 Ohm (5 Volts) Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Effect on shaft of electrostatic voltages determined from different resistances in the shaft grounding cable. Ungrounded (30 Volts) 10k Ohm (4 Volts) 1k Ohm (0.5 Volts) Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” CHART SCALES - ZERO TO 1.0 VOLTS AND 10.0 AMPERES BRUSH CURRENT ONE HOUR 750MW GENERATOR VCM OUTPUT INDICATING A UNIT OR SYSTEM RECURRING CONDITION Figure #11 Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Ground Fault Condition at a Nuclear Power Plant and Root Cause Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Root Cause Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Unit 1 Shaft Peak Currents and Voltages for Six Days Grounding brush Currents = 3.1 and 8.7 Amperes Generator OB End Shaft Voltage = 23.4 Volts Turbine Shaft Voltage = 0.2 Volts Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” Unit 2 Shaft Peak Currents and Voltages over a Day Grounding brush Currents = 2.2 and 6.7 Amperes Generator OB End Shaft Voltage = 14.0 Volts Turbine Shaft Voltage = 4.8 Volts Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” 500 MW Turbine generator Recorded Field Voltage and Peak Shaft Grounding Current During a Field Ground Fault Figure #14 Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” SCModules, Either Voltage or Current, Battery or AC Power, Local Alarm Indications; Remote Analysis VCM-EN-SII Single Enclosure Housing Two Separate VCM-E Boards/Circuits For Large Or Critical Units. Hand-Held VCM or SCMeter or use with SCModules, Displays Voltage or Current Peaks and Averages Also Available… (Explosion-proof Models) VCM-E, AC Powered, Local VCM-C, Battery Power, Local Display, Ungrounded Peak-Voltage And Grounded Peak and Average Ground Current, Max I = 3 Amps. Industrial Type Applications. Display, Alarm LED’s of Shaft Grounding Current And Shaft Voltage. Continuous Signals via 4-20 mA for use in Control Room, via wired or wireless connections. VCM-EN-RM Rack Mount Model configurable with 1 to 4 VCM-E units. MPS’ Family of Shaft Condition Monitors…for Early Detection of Rotating Machinery Faults Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” SHAFT MONITORS provide Early Warning… • Grounding Brush or Ground has lost continuity. • Wet steam conditions at the exhaust end of the turbine causing charge separation with possible blade erosion and cavitation. • Dry Steam conditions at the inlet of the turbine with partial admission, caused charge separation and spark discharge. • Self Excitation or compounding of shaft voltages and grounding currents from shorted rotor coil. Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” SHAFT MONITORS provide Early Warning… • Shaft Rubs at bearings, seals due to oil whip, coupling misalignment, thermal growth, loss of lubrication, impurities in the oil, etc. • Diode Failure in Generator Excitation. • Intermittent Rotor Winding Ground Fault • Loss of or Shorting of Insulation at Bearings, Seals, Gear Teeth and Coupling, etc. • Excessive transients in pulse width modulated rotor and/or stator electrical supply. • Stator core lamination shorting in an electrical generator. Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” • Simplicity and Value - SCM reduces data to basic terms (a fraction of the digital data), while still preserving critical data events • Supported by technology and performance of units installed in the Utility and Petrochemical Industries. • Offers significant enhancement to PDM and Prognostic programs of Utilities, Industry and the Military. • It could be an important input to the decision-making process as to whether a rotating machine is Operational or “Service” Ready. • Alerts at earliest possible problem development requiring • • • confirmation, investigation and possible parts replacement Copyright 2007 Magnetic Products and Services www.gaussbusters.com MPS Gaussbusters are proud to be “Safeguarding Machinery Worldwide” CONCLUSION • SCM Provides Early Warning of Rotating Machinery Problems by Consolidating Signals to the Critical Data And Power Components of the Signals. • Application To Machines Requiring Shaft-riding Brushes And Reliable Monitors. • Integration into existing DCS or CBM systems is straightforward and beneficial. Copyright 2007 Magnetic Products and Services www.gaussbusters.com