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In the international standard ISO 10816-1 "Part 1: General Principles of the Series of Standards for the Measurement and Evaluation of Mechanical Vibration of Machines on Non-Rotating Parts" established by ISO (International Organization for Standardization),3 Measurement 3.2 Measurement Positions, the relevant descriptions of which are excerpted below:
1. Measurements should be made on bearings, bearing supports, or other structural components that respond significantly to dynamic forces and are indicative of the overall vibration characteristics of the machine.
2. In order to determine the vibration characteristics at each measurement position, it is necessary to make measurements in three mutually perpendicular directions.
Sensor mounting for different devices
With reference to the relevant standards of vibration condition monitoring, and combined with the actual experience of equipment fault diagnosis, we summarize that the following principles should be followed when selecting the location and direction of the installation and deployment of condition monitoring sensors:
(1) The installation location should try to select the parts of equipment with high structural rigidity, such as the bearing seat and end cover of the equipment, to reduce the loss of vibration information in the transmission path;
(2) The installation direction should give priority to the direction of high vibration intensity, such as the direction perpendicular to the installation pipeline, the direction of the force of the equipment, the direction of gear meshing, etc., to improve the amplitude of the vibration signal.
Below we focus on several types of industrial equipment commonly found in the field, specifying the recommended installation location and direction of vibration sensors for equipment condition monitoring.
(1) Horizontal motors
Horizontal motors that are reliably mounted on a rigid support, where the drive end drives the load equipment, vibration intensity is greater than that of the non-drive end, and the direction of restraint of the equipment is vertical, so vibration in the horizontal direction is greater than that in the vertical direction in most cases.
Further considering that the longer the transmission distance, the greater the attenuation of vibration signals, horizontal motors, if the selection of single-axis vibration sensors, the installation location and direction of the priority in descending order as follows: the drive end of the horizontal → drive end of the vertical → drive end of the axial → non-drive end of the horizontal → non-drive end of the vertical.
If a three-axis sensor is used, priority should be given to measuring vibration in the horizontal direction, with the installation position and direction prioritized from high to low as follows: drive end horizontal → non-drive end horizontal.
(2) Vertical motors
Normally, the driving end of a vertical motor is close to the mounting plane and better restrained, while the non-driving end is farther away from the mounting plane and has high vibration intensity.
Therefore, when vertical motors deploy single-axis or 3-axis sensors, they should all be preferentially installed at the non-driving end away from the mounting plane, and can be installed at the driving end when conditions do not permit.
2. Drive components
(1) Straight Gear Reducer
Gearboxes can be divided into single-stage gearboxes and multi-stage gearboxes according to the number of transmission stages. To monitor the operating status of a gearbox, at least one vibration sensor is installed on the input shaft and one on the output shaft. For the internal straight gear spur gear reducer, its force direction is mainly along the radial direction.
Therefore, if a single-axis vibration sensor is selected, the installation position and direction are prioritized in descending order as follows: input/output end vertical → input/output end horizontal → input/output end axial.
If a three-axis sensor is selected, priority should be given to measuring vibration in the vertical direction, and it is sufficient to install the sensor in the vertical direction of the input and output shafts.
(2) Helical and bevel gear reducers
For helical gear or bevel gear reducer, its force direction is mainly along the axial direction, and it should focus on monitoring the vibration signal in the direction of the main shaft.
If a single-axis vibration sensor is used, the installation position and direction are prioritized from high to low as follows: input/output end axial → input/output end horizontal → input/output end vertical.
If triaxial sensors are used for condition monitoring, priority should be given to measuring vibration in the axial direction, and it is sufficient to choose to install the sensors in the axial direction of the input and output shafts.
(1) Cantilever centrifuges/fans
Cantilever centrifuges/fans have bearings on one side of the impeller, and the measurement point is usually selected close to the bearing at the drive end. It should be noted that the inlet and outlet pipes of the pumping machine/fan also play a restraining role for the equipment, which to a certain extent suppresses the vibration of the equipment in the direction of the pipes, and the vibration measurement direction should be perpendicular to the inlet and outlet pipes if the conditions allow. However, compared with the fixation of the bolts at the bottom of the pumping machine, the restraining effect of the pipeline is limited. When the pipeline direction is horizontal, it is still preferred to install the vibration sensor in the horizontal direction.
When using single-axis sensors for condition monitoring of cantilevered centrifuges/fans, the installation position and direction are prioritized in descending order as follows: horizontal at the drive end → vertical at the drive end → axial at the drive end.
When using a triaxial sensor for condition monitoring, measurement of horizontal vibration is preferred.
(2) Double-supported centrifuges/fans
Compared with single-supported centrifuges/fans, double-supported centrifuges/fans have bearings on both sides of the impeller, so that both the driving and non-driving ends need to be arranged with measurement points when monitoring.
When single-axis sensors are used, the installation priorities are, in descending order: drive end horizontal → drive end vertical → drive end axial → non-drive end horizontal → non-drive end vertical → non-drive end axial.
If triaxial sensors are used, measurement of horizontal vibration should be prioritized, with the drive end of the installation having higher priority than the non-drive end.
(3) Roots Fans/Twin Screw Compressors
The fan blades in a Roots fan/twin-screw compressor engage in a vertical direction, so vibration in the vertical direction is relatively high. For Roots Fans or Twin Screw Compressors where the distance between the center of the shafts of the active and driven shafts is less than 800mm, one sensor at each end (driven/non-driven) can be used for vertical vibration measurement in the middle of the two shafts. If the distance between the centers of the active and driven shafts is more than 800 mm, the vibration in the vertical direction of the active and driven shafts needs to be collected by installing 2 sensors respectively.
If a single-axis sensor is used, due to the same rotational speed of the active and driven shafts and the same bearing type, considering the cost of the sensor, problems can be avoided by not locating the faulty bearing, and the condition monitoring can be carried out for one shaft.
(1) If the active axis is selected for monitoring, the priority of the sensor mounting position becomes as follows in descending order: the active axis at the driving end is vertical → the active axis at the driving end is axial → the active axis at the non-driving end is vertical → the active axis at the non-driving end is horizontal → the active axis at the driving end is horizontal → the active axis at the non-driving end is axial.
(2) If the driven shaft is selected, the priority of the installation position becomes: driven end driven shaft vertical → driven end driven shaft axial → non-driven end driven shaft vertical → non-driven end driven shaft horizontal → driven end driven shaft horizontal → non-driven end driven shaft axial.
If three-axis sensors are used, the measurement of vertical vibration should be prioritized, and the priority of the sensor installation position and direction should be as follows in descending order: the driving end of the active shaft is vertical → the non-driving end of the active shaft is vertical → the driving end of the driven shaft is vertical → the non-driving end of the driven shaft is vertical.
In the actual site, there are many types of equipment and complex operating conditions, and the installation location and measurement direction of the vibration sensor need to be selected by comprehensively considering the installation method and operating conditions of the equipment. Reasonable installation location is the basis for ensuring the accuracy of equipment operation monitoring, can effectively improve the accuracy of fault diagnosis, create conditions for accurate maintenance of equipment, reduce operating costs and enhance the competitiveness of enterprises.
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