Simple diagnostic method (only to assess whether there is an abnormality)
1. Select the measuring point
(1) Do not change the measuring position to ensure the same premise, preferably the bearing seat.
(2) The contact surface of the probe is smooth and firm.
(3) Generally measured in the vertical and axial directions. There are three directions for speed and one direction for acceleration.
The bearing seat is exposed, and the measuring part is the bearing seat; the bearing seat is inside, and the measuring part is the part or foundation with high rigidity of the bearing seat.
The shock vibration caused by the fault propagates outwards in the form of a hemispherical wave and is transmitted once at the interface of the part, and the energy loss is about 80%. The sensitivity of the sensor is 100% in the bearing direction, 95% in the 45 degree direction and only 2% in the axial direction.
2. Measurement parameters
Bearing vibration frequency ranges from a few Hz to thousands of Hz. Generally, less than 10HZ, displacement measurement; 10HZ to 1KHZ (medium frequency), speed measurement; more than 1KHZ (high frequency), acceleration measurement (commonly used for more than 10KHZ).
Commonly used speed and acceleration, to remove other vibration signals, use a filter to take the required bandwidth. The amplitude of normal working parts follows the normal distribution, and the amplitude distribution of a certain frequency will be more concentrated under abnormal conditions.
3. Measurement cycle
The measurement time interval depends on the economy and does not leak abnormal conditions, the shorter the better.
4. Judging standard
The absolute standard and the relative standard are used together.
There is no absolute standard for all bearings, and the same bearing is used in different cases with different criteria. Therefore, we must pay attention to the use of occasions to select the appropriate criterion.
It is difficult to determine the absolute standard of value judgement of the low-frequency part. The relative standard or relative judgement method is used. Therefore, two judging criteria should be used to judge the high-frequency and low-frequency bearing vibration at the same time.