Energy - Maintenance
GE Energy - "GLITCH" Definition, Sources, and Methods of CorrectingPage 1 of 5EnergyISearchSEARCHONLINE TOOLSPRODUCTS & SERVICESOUR COMMITMENTABOUT USCONTACT US"GLITCH" Definition, Sources, and Methods of CorrectingHomePrint this pageOptimization and ControlApplication Notes"GLITCH"Bently Nevada AssetCondition MonitoringControl SolutionsOilfield TechnologyIIIMechanicalElectricalN onconcentricRotorsResidualMagnetismBO'Aed RotorMelalurgicalMicroscopicSegregationPerformance andOptimization SoftwareReuter StokesMeasurement SolutionsOptimization and ControlProd ucts A-ZIISurfaceIrregularitiesand ImperfectionsILocalizedStressConcentrationsThe term "GLITCH" is Bently Nevada Corporation'snomenclature for describing all forms of vibrationmeasurement error from an observed shaft surface. Thisdoes not include other possible noise and signal errorsources, such as electrical line noise, monitor problems orproblems associated with casing mounted transducers.Casing mounted transducers, such as velocity coils oraccelerometers are also SUbject to signal error sources inthe form of cross axis vibrations, improper mountings, linenoise as well as several others particular to each type oftransducer; however, glitch deals with observed shaftsurface anomalies only. In order to clarify the sources ofthese vibration measurement errors, sometimes referred toas runout, the follOWing diSCUssion shall focus on the twocategories of "GLITCH", mechanical and electricalPredictive Maintenance throughthe Monitoring and Diagnosticsof Rolling Element BearingsREBAM an effective way tomonitor and analyze rollingelement bearing conditionInstallation of ElectricalEquipment in HazardOUs AreasConsiderations when using EddyCurrent Proximity Probes forOverspeed ProtectionApplicationsGuidelines for Grounding(Earthing) Bently NevadaRotating Machinery SystemsStandardized Rules forMeasurement on RotatingMachineryRelated OfferingsMonitoring SystemsSensors and TransducersTest and Calibration EquipmentRelated LinksApplication NotesBently Nevada User ForumCustomer Application CentersCustomer Success StoriesORBIT MagaZineRightrax SensorsSources of GlitchMechanically Induced Runout:Nonconcentric Surfaces/BowsA shaft surface which has been Improperly machined (egg shaped or non concentnc) will yield a Sinusoidaldisplacement Signal with a frequency COincident with the rotational speed of the .-otating element A secondcondition on a rotating element, which will yield the same apparent dynamic motion condition. manifests whenthe rotating element has been physically bent or bowed.Sources of improperly machined surfaces can usually be traced to a worn or defective set of bearings on themachine used for final machining or grinding or a worn-out set of lathe centers on a lathe. Bows in a rotatinghttp://www.ge-energy.com/prod serv/products/oc/en/bently nevadalglitch.htm9/10/201 0
GE Energy - "GLITCH" Definition, Sources, and Methods of CorrectingPage 2 of 5element are typically Introduced due to Improper handling of the rotor dunng its manufactunng cycle Thismay be the result of a sudden or Jarring load applied or due to long-term storage of the element with impropersupports for the rotor In the case of the latter. an Improperly supported rotor may Introduce a permanent sagor bow due to gravitatIOnal forcesSurface Irregularities or ImperfectionsThe presence of surface imperfections or irregularities will yield a runout condition as observed by theproximity transducer The sUliace imperfections discussed herein are Ir1 the form of scratches. dents. burrs,etcIn general. surface Irregularities are created due to improper handling of the rotor during the manufacturingcycle. Care should be taken to protect the shaft surface to be used for dynamic rnotion measurements. Inessence, these surface areas should be given the same protective measures used to protect a bearingjournal surface Crane lifts should be made with cables attached to shaft areas away from the probemeasurement surfaces Support fixtures for storage of rotors should not Introduce surface scratches, dents,etcOccasionally. surface irregularities are introduced via a machine-cutting tool If the too! is dull or the feed istoo rapid, some tool chatter may occur Which can introduce small ripples in the shaft surface.Electrically Induced Runout:Residual MagnetismIn general, proximity transducers will operate satisfactorily In the presence of magnetic field, as long as thefield is uniform or symmetrical and not iocalized to a particular location on the rotor If a particular area orzone of the shaft surface is highly magnetic and the remaining surface is nonmagnetic or at a much lowervalue. an electrical runout condition will manifest. This is due to the resultant change in sensitivity on the shaftsurface to the applied field from the pro)(imity transducers.Residual magnetism runout problems are seldom encountered. However, various physical inspectiontechniques employed during the manufacturing cycle, such as the use of magnetic chucks, can introduceresidual magnetism problems. The most common inspection technique, where residual magnetism may be abyproduct, is a Magnetic Particle inspection (Magnaflux ) to check for cracks on castings, or weldments, orafter other manufacturing cycles. The magnetic field introduced to the rotor for this inspection should beneutralized after the inspection program is completed. This is done with the Magnaflux machine and involvescontinuously reversing the polarity and passing a current through the rotor at continuously decreasingamperes. If done properly. this procedure should neutralize the magnetic properties of the rotor. In somecases a proper polarity reversal is not performed, and residual magnetism is produced.Precipitation Hardening17-4 pH steel nearly always presents an electrical runout problem. Some form of material replacement (shrinka collar, overspray a matenal) IS normally required to eliminate glitch.Other pH steels, such as 15-5 pH, seems less prone to glitch, but any pH steel may cause difficultiesMetallurgical SegregationThe scale factor yielded from a proximity transducer IS dependent upon several variables. One variableinvolves the specifiC metal or metallurgy it is to observe. Typically. steel alloys for shaft matenals contain avariety of alloying agents. In general, the final metallurgical composition of these alloys is a homogenousmixture. On some rotating elements microscopic segregation of the steel alloys may occur. Since theproximity transducer responds with different voltage outputs depending upon specific metals. the lack of ahomogenous metallurgical composition around Ule circumference of a shaft may give rise to varying electricaloutputs.Residual Stress ConcentrationsDuring the normal manufacturing cycle of rotors, a vanety of machining and surface treatment processes canintroduce small amounts of localized stress concentrations Although these stress areas do not adverselyaffect the mechanical properties of the rotor, they may give rise to an electrical runout from the proximitytransducers. Since one of the variables affecting voltage OLitput from the transducer is the resistance of theobserved shaft surface. any deviation of the resistance around the circumference of the shaft (due to varyingstress levels) will produce a voltage change.Measurement of GlitchThe observation of mechanical runout at a rotor speed below which dynamic vibration is eliminated (typicallyless than 10 c/o of the rotor operating speed) on an oscilloscope will yield a SinUSOidal dynamic waveform fornon-concentric surfaces or shaft bows. Surface irregularities or imperfections will appear on an oscilloscopeas sharp voltage spikes superimposed on the dynamic waveforrnhttp://www.ge-energy.com/prod serv/products/oc/en/bently nevada/glitch.htm9110/2010
GE Energy - "GLITCH" Definition, Sources, and Methods of CorrectingPage 3 of 5Nonconcentnc surfaces or shaft bows may also be measured by a dial indicator moun1ed in the probe area ofthe shaft, which in turn, is mounted at the bearing journals in vee blocks. or roller bearings. Thecircumference of the probe area IS marked off In 36 positions (10 degree Intervals) with zero in line axially withthe thrust collar keyway Dial gauge readings are recorded at each Indicated position Two sets of readingsare taken. approximately half an Inch apart axially, one on each side of the probe position centerline. The twosets of readings are averaged to give a record of mechanical runout Amencan Petroleum Institute (API)Standard 670 recommends that "the combined total electrical and mechanical runout does not exceed 25percent of the maximum allowed peak to peak vibration amplitude or 0,25 mil (6 micrometers), whichever isgreater" The shaft surface finish should be from 16 to 32 micro inches (OA to 0.8 micrometers) root meansquare, also per API 670,The observation of a residual magnetism runout condition on an oscilloscope can yield a sinusoidal motionindication. However, tile sine wave wJ!i be distorted and to some extent tend towards a square wave. A finalcheck for residual magnetism embraces the use of a small handheld field strength indicator manufactured byMagnaflux Corp, Holding this meter at the shaft smface and hand turning the rotor will confirm the presenceor absence of magnetic fields of less than 2 gauss with variations less than 1 gaussAn oscilloscope observation of metallurgical segregation will typically indicate a somewhat sinusoidalwaveform With 11igh voltage, high frequency spikes supemnposed on the waveform.Observation of reSidual stress concentrations on an OSCilloscope will yield a sinUSOidal waveform with highvoltage, high frequency spikes supenmposed on the waveformIt should be noted that the oscilloscope waveform in all the above cases may also be very irregular,depending on the number of other shaft surface anomaliesIf desired, the electrical runout can be detemllned by subtraction of mechanical ,unout from the total rUnoutGlitch ReductionVarious methods of reducing glitch are available and have been successfully used by firms. It is not possibleto define which method is best because each can achieve lhe desired result However, it is possible to narrowthe chOice of methods when they are con idered on a cost and time basis,It IS also notable that proper matenal selection, heat treating, and allOWing control can have a large effect onthe runout condition of a rotor. If rotors are to be replaced or rebUilt, it is far more cost-effective to detect andcorrect glitch at the earliest stages of machine assembly.aDegausslng- ReSidual magnetism In a shaft, caused as a result of magnetic particle crack detection orby working in a magnetic field, can produce very senous electrical runout It is therefore prudent tomeasure residual magnetism in the probe area of every shaft before attempting glitch removal. Alocalized residua' magnetism of field strength 5 gauss on a rolling shaft can give an electrical runout inthe order of 0,5 mil. Thus any shaft, which exhibits residual magnetism in excess of 2,0 gauss, orvariations greater than 1 gauss, should be degaussed. This is generally not a complete glitch removalprocess on its own, but it does help to ensure that glitch readings do not change as a result of a shaftlosing residual magnetism in service.b. Diamond Burnishing - This API recommended method has a high success rate of reducing glitch towithin acceptable limits The probe area IS rolled under a diamond-burnishing tool to work a shaftsurface to a uniform finish. In effect, th!s procedure produces an even work-hardened surface, whichrequires no additional treatment This method is undoubtedly the easiest with very little skill required.c. Further Macl1!ning - Should a probe area be oLitside acceptable limits, the target area can be reground,and should be degaussed following grlndll1g. This can be a hit and miss method that could lead to evenmore unacceptable resultsd. Polishing or Stoning - Similar process to Ic) but not qUite so drastic However, the problem of makingmatters worse stili exists.eSleeving - Shrinking a sleeve onto the shaft tlas been used, but It is an expensive way of producingresults as unpredictable as (e) and (d) above. As with both of those methods. further treatment may benecessary,f. Plasma Spray Finishing - Altt10ugh not recommended by API, metal coating has been used effectivelyas a solution for stubborn runout problems Aluminum . Nickel flame spray coatings are currently beingused very successfuliy In the Industry to reduce glitch problems, often to lessl!lan 1/2 mil pp.The Metco@ process consists of machining a 1-1/2 inch Wide. 0.060 deep grove around the shaft, The groovethen grit blasted, and coated with a bond coat of Metco 447 to about 0,010 inch thickness. The remainderof the grove IS then flame sprayed filled with Meteo 52C aluminum Silicon composite and machined flat withIShttp://www.ge-energy.com/prod serv/products/oc/en/bently nevada/glitch.htm9/10/2010
GE Energy - "GLITCH" Definition, Sources, and Methods of CorrectingPage 4 of 5the surface of tile sllaf!. Since the electrical properties are different from 4140 steel, a specially calibratedProximitor must be used at lhese locations.Protection of Probe AreasThe removal of glitch by one or a combination of the treatments discussed above is essential for customeracceptance of levels of recorded vibration Having treated the probe areas it is essential to protect theseareas to prevent corrosion damage, scratching and indiscruninate "cleaning up" During production andtesting, this protection IS afforded by the care taken by skilled craftsmen wr,o appreciate the sensitive natureof this surface.Between acceptance testing and startup much less care can be exerCised There have been many fieldreports of probe areas being damaged by rust scratches or dents Cleaning up the damage by stoning orpolishing may give the desired appearance but ttle onginal glitch recordings would tlave been completelyaltered and undoubtedly taken beyond acceptable limits. Glitch removal then has to be carried out in the fieldby selective micropeening, and conSidering the adverse conditions. the results are Invariably inferior to thosewhich can be achieved In the shop It is therefore recommended that after glitch treatment and recordings aretaken in the shop, the probe areas be given a coating of non-metallic epoxy resin, which can remains, for thelife of the machine. This coating Will not affect probe readings but will protect ttle probe area from corrosionand all minor mechanical damageCompensationObviously, shaft treatment to remove the source of runout IS the most desirable procedure. If this is done,there is no reason to have to "account for" runout rn subsequent vibration signalsHowever, the occasional shaft material or forging may not respond well to the standard shaft treatmentmethods. The shaft may have a "permanent" bow or It may be impossible or Impractical to treat the shaftsurface before a time when Vibration data IS required on a given machine If it IS Impractical to treat the shaftsurface or remove the shaft bow, an electronic method may be used. The following IS an explanation anddiscussion of this application.Vector Nulling - Digital Vector FilterAlso called slow roll compensation; this system IS an integral part of the Digital Vector Filter. It provides ameans for nulling a slow roll vector. It should be noted that the nulling operation IS a true vector subtraction(phase and amplitude) and not merely a voltage suppression circuit. The nulling Circuit operates on the filteredvibration wavefoml (the vector information in the DVF) Since the filter employed in the DVF-3 is tuned to therotational (1 X rpm) frequency of the rotor the nulling circuit eliminates that portion of shaft runout, which iscoincident with the rotational frequency. Typically, it is used to eliminate a 1X component of runout such as abow in the shaft or a nonconcentric (egg-shaped) shaft condition at the probe measurement plane, All higherorders of runout (non 1X components. such as scratches. metallurgical Irregularities. etc.) are eliminatedthrough the filter action of the DVF-3Once the initial slow-roll vector has been nulled, It is automatically subtracted from all future dynamic signals.This system provides the means for properly examining the mechanical response and impedance of asystem, definition of the balance resonances (critical speeds), and amplification factors. over the operatingspeed range. Vector nulling also allows for the compensation of the reSidual unbalance vector after a balanceresonance, and for observation of a higher balance resonance response.It is possible, and even probable on larger machinery, tllat nominal axial position changes and differentialexpansion up to running speed will cause a vibration probe to observe a "new" lateral location on the shaft,When considenng the overall runout pattern this "new" shaft location may be significantly different than theoverall pattern observed with the machine at slow-roll.Vector nulling does not, 11Owever, deal with the overall runout pattern because of the filter in the system. onlythe 1X runout vector is considered The once-peHurn runout vector is not likely to change from slow-roll tooperating speed and tel11peratul'e. In this regard, vector nulling offers a distinct advantage over any other typeof digital runout compensation. Vector nu!llng also offers the capability of nullll1g the residual vector of shaftmotion after passing through a resonant speed region to observe the action of the next higher resonancewhen Bode plots (amplitude vs rprll and phase vs rpm) are madeRecommendationsThe above considerations lead to the follOWing conclUSions and recommendations by Bently Nevada:Glitch can often be controlled at its source (the shaft) to a Jevei acceptable for monitonng purposes, andin most cases to levels usable for machine acceptance testing and diagnostic purposes. Everyreasonable attempt should be \nade to correct the runout problem at its source2 The use of electronic run out compensation for continuous machine monitOring should be avoidedexcept in rare cases (e g. a damaged srlaft that cannot be corrected until the next turnaround). Bentlyhttp://www.ge-energy.com/prod serv/products/oc/en/bently nevada/glitch.htm9110/2010
GE Energy - "GLITCH" Definition, Sources, and Methods of CorrectingNevada does not recommend the use of electronic runout COlllpensatlonWired for automatic machine shutdown.Page 5 of 5Ina vibration monitor system3Nul!lIlg - compensation for an initial 1X vector - can be accomplis fled with the Digital Vector Filter 34When reproducillg vibration data from magnetic tape special care should be taken to ensure propersynchrollization of the signal Most tape recorders provide a function whereby one channel can bededicated as a synchronizing Signal for tape flutter compensation5. When runout compensation IS used, it should be used as a "last resort" In all cases, both the anginaltransducer signal and the compensated signal must be available for observation on externalIIlstrumentsReferences"New Techniques 'n overcomlllg Electrical Runoul' by Dale W Beebe, Turbodyne Corporation, HydrocarbonProcessing August 1976.Electrical Runout and Eddy Current Displacement Proximity Transducers, by Biggs, David H , ASME Paper,September 1975. (Bently Nevada Literature No, L0360)Elliot-Wledeke paperAPI 670, Second edition, Section 4 12 Machine Shaft Requirements for Electrical and Mechanical RunoutPrint this pageGE Energy Home I Products I Services I Lifecycle Services! Online Tools i Our Commitment 1About Us I GE Careers I Customer Advocate I SiteMapGE Corporate Home I Investor Information I Privacy Policy 1 Terms of UseCopyright General Electric Company 1997-2010http://www.ge-energy.com/prod serv/products/oc/enlbently nevada/glitch.htm9110/2010
square, also per API 670, The observation of a residual magnetism runout condition on an oscilloscope can yield a sinusoidal motion . indication. However, tile sine wave wJ!i be distorted
on work, power and energy]. (iv)Different types of energy (e.g., chemical energy, Mechanical energy, heat energy, electrical energy, nuclear energy, sound energy, light energy). Mechanical energy: potential energy U mgh (derivation included ) gravitational PE, examples; kinetic energy
Forms of energy include radiant energy from the sun, chemical energy from the food you eat, and electrical energy from the outlets in your home. All these forms of energy may be used or stored. Energy that is stored is called potential energy. Energy that is being used for motion is called kinetic energy. All types of energy are measured in joules.
reduces Kinetic Energy and increase Potential Energy A: The energy is stored as potential energy. PE is like your saving account. Potential energy gain (mg h) during the rising part. We can get that energy back as kinetic E if the ball falls back off. During falling, Kinetic Energy will increase mg h. Potential energy will reduce mg h.
Energy is often defined as the ability to do work. Pair up and list as many forms of energy as you can. Electrical. Chemical. Nuclear. Magnetic. Elastic. Sound. Gravitational energy. Kinetic energy (energy of motion). Thermal energy (heat energy). Potential energy. Potential energy
kinetic energy and potential energy as the ball moves. The bars in the figure show that the ball's total energy does not change. The Law of Conservation of Energy The total energy in the universe is the sum of all the different forms of energy everywhere. According to the law of conservation of energy, energy can be transformed from one
changes to thermal energy. Thermal energy causes the lamp's bulb to become warm to the touch. Using Thermal Energy All forms of energy can be changed into thermal energy. Recall that thermal energy is the energy due to the motion of particles that make up an object. People often use thermal energy to provide warmth or cook food. An electric space
32 Renewable Energy 33 References To learn more about DOE programs in energy efficiency and renewable energy, visit the Office of Energy Efficiency and Renewable Energy's web site at www.eere.energy.gov "High energy costs can really pinch American families. While the Department of Energy is working hard to develop new technologies to
transformations. Describe an energy transformation that took place in each of the numbered events above. Solution: 1. Electrical energy to sound energy; 2. Electrical energy to radiant energy (light and heat); 3. Chemical energy from food to kinetic energy; 4. Chemical energy from natural gas to radiant energy (heat and light). 1.
