Standards for motor vibration speed and amplitude
Equipment life and operational safety are directly related to the intensity of motor vibration. Just stating "large vibration" is not enough. Scientific quantitative indicators must be used when measuring.
Amplitude velocity acceleration distinction
For what we usually call vibration, there are three physical quantities that can accurately describe it. Among them, the unit of amplitude is millimeters, which refers to the maximum distance that a vibrating object deviates from its relative equilibrium position. Simply put, it is the amplitude of the vibration when it swings back and forth. The unit of vibration speed is millimeters per second, which reflects the speed of vibration changes within unit time and is closely related to the amount of energy. It is also a key parameter for evaluating the impact of vibration on mechanical fatigue damage.
Vibration acceleration has a specific unit, which has a measurement unit of millimeters per square second. It describes the severity of the change in vibration speed and is often used in the analysis of vibration impact and high-frequency components. In 振幅杆加工 in the category of rotating equipment such as motors, vibration speed is a very commonly used evaluation indicator because it is directly related to structural stress and potential risk of failure. Understanding the differences between these three units is actually the basis for correct vibration measurement and diagnosis.
Interpretation of motor vibration speed standards
For small and medium-sized motors, there are clear international and domestic standards for vibration. These vibration standards mainly rely on vibration speed to classify levels. Taking a motor with a shaft center height in the range of 132 to 225 mm as an example, the standard divides different limits based on the motor's speed. When the motor speed is in the range of 600 to 1800 revolutions per minute, once the corresponding effective value of the vibration speed exceeds 1.8 millimeters per second, it is an ordinary level situation, that is, it just reaches the standard level.
To reach a higher level of standards, the vibration speed must be controlled within 1.12 millimeters per second; if you want to get an evaluation like an excellent grade, the vibration speed must be lower than 0.71 millimeters per second. What this set of data shows is that under the same medium and low speed conditions, the requirements for the smoothness of motor operation are extremely strict.
High speed motor standard differences
When the motor speed increases to the high-speed range of 1800 to 3600 rpm, the corresponding vibration limit is also relaxed. At this time, the allowable vibration speed of the ordinary grade is increased to 2.8 mm per second, the first grade standard is the motor vibration speed and amplitude standard of 1.8 mm per second, and the excellent grade is 1.12 mm per second. This adjustment is due to the fact that when the same vibration energy is generated at high rotational speed, its amplitude will be smaller.
The loss effect of vibration energy on the structure may enhance the amplitude rod machining . The standards are not relaxed in equal proportions. This distinction reflects the scientific nature of the standard formulation, avoids the use of low-speed standards for high-speed motors, and ensures that high-speed equipment has a reasonable safe operation range.
Amplitude and state correlation
An important reference is the amplitude itself, not just the vibration speed, especially when making preliminary judgments or when analyzing specific frequencies. Field experience will correlate the double amplitude value of vibration displacement with the status of the equipment. For example, if the amplitude is less than 0.05 mm, the equipment is generally considered to be in good operating condition. When the amplitude is between 0.05 and 0.12 mm, it is within the acceptable normal or good range.
If the amplitude exceeds 0.12 mm, it often means that the equipment may be unbalanced, misaligned, or loose, and you must pay attention to it and conduct inspections. This method of making judgments based on the intuitive amplitude range provides equipment maintenance personnel with a quick assessment method, but more accurate analysis requires combining vibration speed and acceleration data.
Acceleration evaluation system
Vibration acceleration has its own evaluation criteria, which is particularly critical when evaluating high-frequency impacts such as bearing defects or gear meshing. A common simple evaluation system is as follows: when the vibration acceleration value is less than 9.8 meters per second squared, the motor is in excellent condition. When the acceleration value is between 9.8 meters per second squared and 39.2 meters per second squared, the status is good and can continue to operate, but it requires attention.
If the measured value indicating how fast the object's speed changes over time exceeds 39.2 meters per second squared, it means that the equipment is most likely to be in an abnormal condition, such as the raceway is damaged or the tooth surface is peeled off. At this time, the machine must be stopped immediately for inspection and repair. This system complements the vibration velocity assessment and cooperates with the amplitude rod machining to build a more complete network for vibration diagnosis.
Correct measurement method practice
Before starting to measure, be sure to select the appropriate physical quantity based on the purpose. When measuring the vibration speed, you need to turn the instrument switch to the speed position and make sure that the arrow in the display unit points to millimeters per second. For general motor vibration assessment, speed gears are usually used for measurement.
If there is a situation where high-frequency impact faults are to be detected, the switch should be placed in the acceleration gear, and the unit arrow of the acceleration gear should point to meters per square second, and the high-frequency or low-frequency filter gear should be selected according to the corresponding situation. When measuring amplitude, the displacement gear is selected, and the unit arrow of the displacement gear points to millimeters. Correct gear selection is the first step to obtain effective data. Wrong settings will cause the diagnostic conclusion to completely deviate from the facts.
When conducting on-site inspections, you are more inclined to refer to the kind that can bring an intuitive feeling of amplitude as a basis, as well as the vibration velocity measured by using a vibrator, or other acceleration measurement data to make a final judgment. Do you want to do this here? You are welcome to share your personal experience and more opinions here.
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