Accurate Identification and Early Warning of Bearing Failures
The company mainly produces three core series of products: cylindrical roller bearings, self-aligning roller bearings, and thrust self-aligning roller bearings. The product can be adapted to multiple industrial fields such as metallurgical equipment, mining machinery, heavy machinery, engineering equipment, etc., and can meet the operational and load-bearing requirements of equipment under different working conditions.
SZ Bearings
In modern industrial production, rolling bearings are the core components of rotating machinery, and their condition directly affects the stable operation of equipment and production efficiency. Should a bearing fail, the consequences range from increased equipment vibration and noise to unplanned downtime, resulting in significant financial losses.
Therefore, timely and accurate fault diagnosis of rolling bearings is of paramount importance.
Traditional ‘inspection, listening, questioning and palpation’-style rounds are no longer sufficient to meet the high demands of modern industry for equipment reliability. Today, experienced maintenance engineers are akin to ‘master physicians’ within the factory; relying on a range of precision diagnostic instruments, they ‘take the pulse’ of equipment, facilitating the transition from reactive repair to predictive maintenance. This article will provide an in-depth analysis of the three core ‘tools’ in rolling bearing fault diagnosis—portable vibration analysers, impact pulse/resonance demodulators, and online monitoring systems—and, drawing on practical application scenarios, explain their operating principles and diagnostic value.
The ‘stethoscope’—portable vibration analyser: Pinpointing the source of faults Vibration is a direct reflection of the operating condition of mechanical equipment. When damage such as wear, spalling or cracks occurs in the inner ring, outer ring, rolling elements or cage of a rolling bearing, periodic impact forces are generated during operation, thereby exciting specific vibration signals. A portable vibration analyser is akin to
a ‘master physician’s stethoscope’, capable of capturing and analysing these faint vibration signals to pinpoint the source of the fault with precision.
Working Principle
The vibration analyser collects vibration signals from the bearing housing via an accelerometer and uses Fast Fourier Transform (FFT) technology to convert the time-domain signal into a frequency-domain spectrum. On the spectrum, different types of bearing faults exhibit unique “failure characteristic frequencies”
Outer ring fault characteristic frequencies: When the outer ring raceway is damaged, an impact is generated each time a rolling element passes over the damaged point; the frequency of this impact is related to the bearing’s geometric dimensions, rotational speed and contact angle.
Inner ring fault characteristic frequencies: The impact frequency generated by inner ring damage also follows a specific formula; however, as the inner ring rotates with the shaft, the primary fault frequency is typically accompanied by sidebands spaced at the rotational frequency. This is a key indicator for identifying inner ring faults.
Characteristic frequencies of rolling elements: Damage to the rolling elements themselves (such as pitting or cracks) generates vibration components related to their rotational frequency.
Characteristic frequencies of the cage: Wear or deformation of the cage induces low-frequency vibrations related to its rotational frequency.
By comparing the peak frequencies in the measured spectrum with the theoretically calculated characteristic frequencies, engineers can accurately determine which component of the bearing is faulty. For example, at a machining centre belonging to an automotive parts manufacturer, abnormal spindle vibration was observed. Vibration spectrum analysis revealed an excessively high 2x rotational frequency component, which was ultimately traced to a misalignment issue caused by loose coupling bolts; following recalibration, the vibration amplitude decreased significantly.
Application Benefits
Portable vibration analysers offer flexible operation and are ideal for rapid on-site diagnostics. Not only can they detect obvious faults that have already occurred, but they also enable trend analysis to monitor changes in vibration amplitude, predict the progression of faults, and provide a basis for maintenance decisions.
II. ‘Microscope’ – Impact Pulse Analyser/Resonance Demodulator: Detecting Early Micro-Damage
Fatigue failure in bearings often begins with minute pitting or cracks on the raceway surface. In the early stages of failure, the impact energy generated by these micro-damages is extremely weak and easily drowned out by background noise, making it difficult to detect using conventional vibration analysis. At this stage, a ‘master technician’ must employ a more precise ‘microscope’
— an impact pulse analyser or resonance demodulator.
Working Principle
Both the impact pulse method and resonance demodulation technology fall under the category of high-frequency vibration detection techniques. Their common feature is a focus on capturing high-frequency stress waves (also known as acoustic emission signals) generated by minute internal defects within the bearing.
Impact Pulse Method: This method utilises the transient impact force generated when a damaged area of the bearing comes into contact with the rolling elements; this impact force excites the natural frequencies of the bearing and the sensor system. The instrument assesses the extent of bearing damage and the lubrication condition by measuring the amplitude and frequency of the impact pulses. The LR value and HR value are commonly used assessment indicators, with the LR value reflecting the lubrication condition and the HR value reflecting the extent of damage.
Resonance Demodulation Technology: This technique first extracts high-frequency resonance signals containing fault information via a bandpass filter, then performs envelope demodulation to convert the high-frequency modulated signal into a low-frequency envelope signal. By performing a spectral analysis on this envelope signal, the bearing’s characteristic fault frequencies can be clearly identified, even when the fault features in the original vibration signal are extremely faint.
Both techniques are highly sensitive to early-stage faults and can provide early warning before visible damage to the bearings occurs. For example, at a heavy machinery factory, the combination of vibration analysis and impact pulse technology identified ‘precursors to inner ring spalling’ in three motor bearings 15 days in advance, thereby preventing a disaster.