However, if the outer race of the bearing is cocked in the housing, or the inner race is cocked on the shaft i. Additionally, the bearing race likely has a much lower ductility which means that if there was a corrosion pitflaw. Outer bearing race defect bend shaft cracked rotor end rings inner bearing race defect static airgap irregularities shorted rotor field windings open or short circuit of stator windings ball defect dynamic airgap irregularitrain defect ties 1 s s f p f s when. The peakvue brand of enveloping technique was used successfully by the author in detecting a cracked inner race on a fan bearing. The crack may be initiated from material defects such as inclusions and, owing to presence of tensile stress, grows upward and finally breaks the surface, leading. Defense technical information center compilation part notice. The challenge becomes one of detecting and quantifying the stress wave activity relative to energy and repetition rate. In the case of ball bearings, the bearing has inner and outer races and a set of balls. Bearing failure can take place because of wear and improper installation. However, ultrasonic emissions degrade quickly each time they move through an interface.
Brinelling and why bearings fail linear motion tips. A sphericalroller bearing inner race has a fractured small rib caused by improper installation tools. This bearing defect was not seen in the normal velocity data but was easily seen in the peakvue data. Aviation maintenance alerts federal aviation administration. Picture of the defective bearing with a significant inner race defect identified by. A corresponding surface map of the dent is shown in fig.
There is a crack in the bearing inner ring, straight through the hardened steel, all the way across. Thus, in principle, the ball contacts each race at a single point. Dynamic analysis of a rotorbearingsfd system with the. Based on my findings, i advised the site that catastrophic failure of the bearing was probably not imminent, but the bearing should be changed in the near. As you mounted the bearing inner ring on the tapered shaft, the stresses on the ring increased. Like others have said it also shows early stages of other defects as well.
This is the first known defect of this type for this part. Sufficient data was available to demonstrate the importance of trending for the inner race defect case. Analysis of bearing outer race defects in induction motors. Active magnetic bearings used as exciters for rolling. This assumes the inner race is rotating and that it is in a horizontal machine where gravity imparts a radial, rather than axial, force on the bearing.
It will always be accompanied by a marked increase in vibration, indicating an abnormality. Active magnetic bearings used as exciters for rolling element. Your task at the cement plant today is to replace the wornout bearings on a. Aug 12, 2017 the characteristic defect frequencies are widely used for diagnosing the local defect of the ball bearing. Poor lubrication of the fan bearing is also a potential issue and this should be addressed. Timken engineers give a stepbystep process for an accurate and complete analysis when investigating any bearing damage or system breakdowns. Place the heated inner race solid against the cold shoulder on the shaft until the inner race grabs on to the shaft. In order to indicate this issue, a semianalytical methodthe harmonic balance. Journal of low frequency noise, fault detection enhancement. The active health monitoring of rotordynamic systems in the presence of bearing outer race defect is considered in this paper.
Flaking and pitting occur early in a bearings service life under the following conditions. This was typical of throughhardened e52100 bearing steel. Bearing inner race 123bearing online bearing expert. A tapered roller bearing inner race cone with spalling from debris contamination bruises. Optimal feature set for detection of inner race defect in. Radial bearings include an outer ring with a concave spherical surface.
The system is purported to detect a defect before it breaks the surface of the bearing race. The result is a cracked ring regrettably, a preventable damage. Rotor dynamics analysis have been performed by different authors in the past. Distinction of roller bearing defect from gear defect via. Bevel on driver for larger inner bearing was slightly oversized and didnt fit.
This type of failure is progressive and once initiated will spread as a result of further operation. Severe brinell marks can cause premature fatigue failure. This basic pattern is repeated once per revolution of the highspeed gearbox shaft and is highly suggestive of a single, innerrace defect in a bearing on that shaft. The characteristic defect frequencies are widely used for diagnosing the local defect of the ball bearing.
Defect free bearing, bearing with inner race defect and bearing with outer race. Not necessarily, heat treating is a huge factor in the speed of attack. Initially, the extremely narrow, sharp spike appearance in figure 2. Condition monitoring of ball bearing using vibration analysis. Bearing failure has been studied extensively and numerous methods have been developed for fault detection. In some cases a crack may not be readily visible, but large enough to create fine metal chips that will deteriorate the bearing. Cracked bearing race detection in wind turbine gearboxes. Monitoring gear boxes with peakvue niagara frontier. A bearings smooth performance is assured by a combination of four basic working parts fig. There are two different types of spherical plain bearings. I have seen the retaining nut on a tapered bore come loose and allow the inner race to move, increase the internal clearance, and eventually spin on the journal.
A single axial crack has propagated completely through the inner ring. Each race is a ring with a groove where the balls rest. Hot oil pots, with a tray or hook to support the bearing cone inner race, effectively ease the installation of tight inner races on shafts. This short case history does a good job of illustrating the power of enveloping and high frequency techniques at identifying bearing defects. Chapter 8, vibration in bearings section 7, calculations for bearing defect frequencies. The groove is usually shaped so the ball is a slightly loose fit in the groove. Vibration, stator current, acoustic emission and shock pulse methods spms for the detection of a defect in the outer race of induction motor ball bearing have been compared. Vibration signal was acquired by piezoelectric accelerometer and output was fed to fft analyzer for frequency domain analysis of signal. These include mounting bearings on shafts by applying pressure or blows to the outer race, mounting bearings into a housing by pressing on the inner ring, loose shaft fits, loose housing fits, excessively tight fits, outofround housings and a poor finish on the bearing seat. The cause is unknown and i have no recommendations to prevent recurrence at this time. Bearing defect bpfo with run speed sidebands vibration. Inner race faults have an additional characteristic.
The peakvue brand of enveloping technique was used successfully by the author in detecting a cracked. A model for the highfrequency vibration produced by a single point defect on the inner race of a rolling element bearing under radial load is extended to describe the vibration produced by. Symptoms of a defective cv axle in a car it still runs. Pdf detection of crack initiation in the ball bearing using fft. The amplitude modulation comes from the fact that the defect on the inner race moves in and out of the bearing load zone once per revolution. Use an inner primary bearing race puller to remove the existing race from the mainshaft and discard.
Failure anaysis of ball bearings metallurgical technologies. D slightly smaller than the bearing race so it did the job. The deviation of the measured width from the actual, using the proposed method, is sought below 5%. During mounting, that chip got lodged between the bearing bore and the shaft seat. Inspect bearing for excessive radial and axial wear in accordance with appropriate bearing wear limits in table 92. As the inner race rotates with the shaft, the defect moves from within the load zone of the bearing to outside the. Any static overload or severe impact can cause brinelling. The shaftkeyrotor are probably not hardened to around 6070 hrc the way the bearing race likely was. The heated inner race will pull away from the cold shoulder unless held in position. Unfortunately, much of the information required is not always readily available, so the use of. The waterfall trend diagram at the top race defect and the spectrums after replacement of the bearing. Vibration in bearings calculations for bearing defect.
Defect in bearings mismounting of bearings defect in sealing device, contamination of water, dust or other foreign matters, or shortage of lubricant 1 fracture occurring immediately after bearings were mounted or within a short time after mounting 2 fracture occurring immediately after overhaul 3 fracture occurring immediately. Only radial load is applied with the help of load cell. The experimental localized fault signals vibration acceleration signals were. Rolling element bearing problem vibrationsteknik ab.
Proper installation of bearing components know your parts. I was still able to use it by simply flipping the driver over and using the back side to drive the race. Antifriction bearing defects inner race, outer race, cage, rolling elements 10. The cv constant velocity axle is a very important component in most rear and frontwheel drive vehicles. Peakvue has saved me many times by picking up a cracked inner race on paper machine rolls. Hard particles caused contamination bruising on this spherical roller bearing. Study for ball bearing outer race characteristic defect. The chip is about the size of a fingernail trimming, embedded in the shaft. What i learn from this is not every bearing defect reacts the same.
Bearing 1 failed with one visible axial crack on the inner ring raceway. Timken bearing damage analysis with lubrication reference guide. The worst case scenario would have been if the inner race had cracked and the impeller had worn down. Identification of broken or distorted blades from modulation of the blade passing frequency. If the defect is on the inner race of the bearing, the turning speed will amplitude modulate the bearing tones, and this will cause sidebands around the bearing tones, spaced apart at 1x, to appear. It was immediately noted that the grease in the four bearings had turned to a thick viscous black sludge, full of particulate. No longer self centering, but it was the correct o. Fault diagnosis of power components in electric vehicles. Ball passage frequency, outer race bpfo the rate of which the ballroller passes a defect in the outer race. Outer race also called outer ring or cup inner race also called inner ring or cone rolling elements either balls or rollers separator also called cage or retainer the outer race, or cup, is the bearings exterior ring.
To initiate the crack artificial vnotch defect in the inner race of the ball bearing was induced and the bearing is made to run for 124 hours under. A stress wave races through the metal components, causing the components to vibrate due to resonance. Diametrically opposite cuts were made in the outer races of the four seized bearings. Axial wear is measured parallel to the shaft or bolt which mates with the inner race or spherical ball of the. Understanding the root causes of axial cracking in wind turbine. It is clear that the vibration amplitudes aggravate obviously under the electromagnetic force. The remedy is to replace the bearing or consider redesigning to use a bearing having a greater calculated fatigue life. An inner race defect must move from the defect into the roller, then. Detection of fault in rolling element bearing using condition. By connecting two fixed rotating shafts with a set of cv joints, the axle maintains steering stability while handling the ups and downs from the vehicles suspension. In every case my normal spectrum reading did not show any inner race defect but it was easily seen in the peakvue reading. The theoretical outer race defect frequency calculated by eq. Ball passage frequency, inner race bpfi the rate of which a ballroller passses a defect in the inner race.
Axial cracking in bearing races has become all too common in large. Radial wear is measured 90 from the shaft or bolt which mates with the inner race or spherical ball of the bearing. The signal which one of these cases gave was an inner race defect, but when removed, there was no damage to the inner race, only damage to the shaft and the id of the inner ring. Amplitude modulation in machine vibration signatures. Bsf ball spin frequency frequency emitted when a rolling element bearing with a superficial defect impacts the inner or outer races. The outer races were then parted from the rest of the bearings to facilitate visual examination. Apr 21, 20 timkens 14 step procedure for bearing analysis. The outside diameter of the inner ring, or ball, has a convex spherical surface.
Detecting bearing faults part 2 metaltometal contact sets off a ripple effect. Part 1 bearing failure can grind your operations to a halt, resulting in significant lost time and. Overloaded bearings must be repaired or replaced, or you run the risk of further damage and. This is a common example of an antifriction bearing assembly defect.
Chemical composition analysis of a large seized bearing inner race, outer race, and ball was performed according to astm e41999a. The varying compliance vc frequency of a faultfree rotorbearing system equals to the bpfo ball bearing outer race defect frequency due to the internal kinematic relationship of a bearing assembly. One of the common modes of failure in a rolling element bearing is a point defect on the inner race or the outer race of the bearing. The hardness of the inner and outer races from the same seized large bearing was measured to be 61 hrc, respectively. An inner race fault about 38 of an inch wide and 1 inch across the bearing was found figure 4. If the inner race has a small defect such as a crack, this defect will move in and out of the bearing load zone at the rate of the shaft rpm. Bearing with cracked inner race this short case history does a good job of illustrating the power of enveloping and high frequency techniques at identifying bearing defects. Cracked inner race question amp maintenance forums. Feb 10, 2014 a sphericalroller bearing inner race has a fractured small rib caused by improper installation tools. Outer race also called outer ring or cup inner race also called inner ring or cone rolling elements either balls or rollers separator also called cage or retainer. The frequency spectrum of a faulty rolling bearing includes not only the inner and outer races.
The third case demonstrates severe cracked teeth in a precision tension bridle gearbox. Radial ball bearing inner race defect width measurement. The shaft is assumed to be supported by conventional mechanical bearings and an active magnetic bearing amb is used in the mid of the shaft location as an exciter to apply electromagnetic force to the system. Identification of cracked or broken teeth from impulsive modulation of the tooth meshing frequency turbine blades. If the bearing had not been replaced it is possible the size and caused to bearing to fail, which would lead to possible catastrophic failure of the ventilation.
A number of conditions can cause denting, wear, cracked rings, high operating temperatures, early fatigue and premature failure of bearings. Bearing with cracked inner race vibration institute. An inner race defect must move from the defect into the roller, then through the roller into the outer race, and finally through the outer race to the accelerometer on the machine surface. Inner primary bearing race puller shown in picture 1. Timken bearing damage analysis with lubrication reference. Vibration analysis gear bearing mechanical free 30.