Four Installation Methods of Vibration Velocity Sensors

Vibration velocity sensors are generally used to measure bearing vibration, and in a small number of cases, they are also applied to measure rotating shaft vibration. When measuring vibration velocity, improper or insecure installation of the sensor will lead to distorted measurement results or sensor damage caused by vibration. This article introduces four installation methods of vibration velocity sensors for your reference.

Vibration velocity sensors are generally used to measure bearing vibration, and in a small number of cases, they are also applied to measure rotating shaft vibration. When measuring vibration velocity, improper or insecure installation of the sensor will lead to distorted measurement results or sensor damage caused by vibration. Therefore, we must carefully select the installation method for vibration velocity sensors.

When sensors are adopted to measure rotating shaft vibration, four on-site installation methods are commonly used: hand-held fixation, plasticine adhesion, permanent magnetic chuck fixation and bolt fixation. For temporary vibration measurement, the hand-held sensor method is mostly adopted. This method features flexible measurement and convenient operation, and has unique advantages especially when there is a shortage of vibration velocity sensors and poor sensor interchangeability. Its disadvantages lie in relatively large test errors and high labor intensity.

Adhering sensors with plasticine is also quite convenient, and the accuracy of measurement results is much better than that of the hand-held method. It should be noted that plasticine cannot attach vibration velocity sensors to vertical planes and can only fix them on horizontal planes, for instance, measuring vertical, horizontal and axial vibration at the top of bearing housings. With firm adhesion, this method can measure a maximum vibration displacement of 300 μm at a frequency of 50 Hz.

Another drawback of plasticine is that its adhesive force is greatly affected by temperature; both excessively high and low temperatures will significantly reduce its adhesion. Hence, it is not suitable for fixing vibration velocity sensors used in measurements on high-temperature high and medium-pressure rotors of steam turbines and bearings equipped with wheel discs. It is also not advisable to use this method during cold startup in winter when the bearing temperature is too low.

Fixing velocity sensors with permanent magnetic chucks is more convenient than the plasticine method. At present, domestic manufacturers can produce permanent magnetic chucks with dimensions of φ50 mm or 50 mm × 50 mm, which can generate a suction force of up to 196 N. Such chucks can secure vibration velocity sensors weighing less than 500 g on horizontal surfaces, supporting a maximum measurable vibration displacement of 1000 μm. The downside is that the surfaces of most unit bearing housings are coated with putty or paint, which weakens the suction force of the chuck. As a result, auxiliary hand support is required when attaching the chuck to vertical planes under large vibration amplitudes to prevent the sensor from falling off and being damaged.

Directly fixing velocity sensors to bearings with bolts enables reliable measurement of vibration in three directions at the top of bearing housings, as well as vibration in two directions on vertical planes. This installation method offers the firmest fixation among the four approaches.

In summary, the installation of vibration velocity sensors should match measurement requirements and different working environments by selecting the most suitable one among the four above methods. Only in this way can smooth measurement be guaranteed and measurement and test errors be minimized.