Operation Process and Detection Content of Bearing Testing Machines

Operation Process and Detection Content of Bearing Testing Machines

For bearing testing machines, the testing direction, methods, reference data to be adjusted during the test, and comparison standards vary according to different bearing conditions. Below, Kaiyuan’s editor will detail the operation process and detection content of bearing testing machines.

I. Operation Process of Bearing Testing Machines

1. Selection of Measuring Point Positions

Different mechanical bearings have different installation methods and structures. Some bearings are mounted on bearing housings that are exposed, so the measuring points (i.e., sensors) should be arranged on the bearing housings. Others are installed inside machinery or directly on the box body; in such cases, the measuring points should be selected at positions with high connection stiffness on the bearing housing or suitable locations on the box body.

2. Selection of Measuring Point Directions

The measuring direction should be determined based on the load-bearing condition of the bearing. If the bearing bears radial load, radial vibration should be measured; if it bears axial load, axial vibration should be measured; if it bears both radial and axial loads, sensors should generally be arranged in both directions. Sensors should be placed as close as possible to areas with high load density to ensure the acquisition of maximum vibration signals from the bearing itself.

3. Determination of Measurement Standards

(1) Definitive Standards

Definitive standards are formulated after specifying correct measurement methods. They include international standards, ministerial standards, industry standards, and enterprise standards, etc. When using definitive standards, measurements must be performed with the same instruments, at the same location, and under the same conditions. Attention should be paid to mastering the applicable frequency range and measurement methods of the selected standard.

(2) Relative Standards

Relative standards involve periodically measuring the same location, comparing the results over time, and taking the value under normal conditions as the reference value. Judgments are made based on the multiple ratio of the measured value to the reference value. For low-frequency vibration, the measured value reaching 1.5~2.0 times the reference value is usually designated as the attention zone, and approximately 4 times as the abnormal zone. For high-frequency vibration, the attention zone is when the measured value reaches 3 times the reference value, and the abnormal zone is around 6 times.

(3) Comparative Standards

Comparative standards refer to criteria for judging by conducting vibration detection on the same location of several bearings of the same model under the same conditions and comparing their vibration values with each other.

II. Detection Content of Bearing Testing Machines

Temperature, noise, and frequency are the three key elements of bearing diagnosis, but they are not closely correlated in the early, middle, and late stages of common faults. Abnormal noise and frequency do not necessarily cause temperature rise, and temperature rise does not mean the bearing is damaged.

1. Vibration Characteristic Level

Due to production and processing factors, some newly installed bearings have characteristic frequencies of certain bearing components (usually the characteristic frequencies of the inner and outer rings of the bearing), resulting in higher speed values. However, the amplitude does not increase and may gradually decrease with extended operation time. This situation does not endanger the practical application of the bearing, but it only applies to newly installed bearings. Taking advantage of the characteristics of bearing high-frequency vibration (fast attenuation and difficult transmission), the speed and instantaneous speed amplitude of each bearing can be accurately measured. The amplitude difference between faulty bearings and normal bearings is significant, especially the instantaneous speed amplitude, which can differ by several to dozens of times.

2. Temperature Characteristic Level

Bearing temperature rise is generally caused by bearing defects or lubrication issues. If caused by bearing defects, it indicates the fault has reached the middle or late stage. The focus of temperature characteristics is on temperature rise rather than just the temperature value. However, sometimes both temperature rise and increased high-frequency vibration are caused by lubrication problems rather than bearing defects. A common method to verify lubrication is to add new grease and observe the vibration response. If the vibration returns to normal afterward, it indicates the issue is lubrication-related. If the vibration recurs after several or more than ten hours, the bearing has defects.

3. Noise Characteristic Level

Bearing faults are usually accompanied by noise, and different faults produce different noises, which require rich on-site experience to distinguish. Clear and single noise is usually caused by certain common faults and generally does not lead to a rapid temperature rise, leaving sufficient time for scheduled maintenance. However, if other noises indicate obvious friction and the temperature rises significantly, the bearing must be replaced immediately. Intermittent abnormal noise is generally caused by internal defects of the bearing. As the bearing rotates, the defect also rotates; when entering the load zone, the defective side of the bearing surface may not be under load, resulting in no abnormal noise being heard.

The above is the complete content of the operation process and detection content of bearing testing machines, including the determination of bearing measurement positions, directions, standards, etc. Kaiyuan has rich experience in the R&D and production of bearing testing machines and can meet the testing needs of bearings of various specifications and models. For more questions, please feel free to call us for consultation.