JB/T 8698-1998 This standard specifies the vibration limits of ventilators. This standard also specifies the measurement location for measuring ventilator vibration, the requirements for measuring instruments, the installation of the measured product, and the operating conditions during measurement. This standard applies to factory inspection, type testing, and acceptance of vibration indicators of centrifugal, axial flow, and mixed flow ventilators. JB/T 8689-1998 Vibration detection and limits of ventilators JB/T8689-1998 Standard download decompression password: www.bzxz.net

JB/T8689-1998
Appendix A of this standard is a reminder appendix.
This standard is proposed and managed by the National Technical Committee for Standardization of Fans. The responsible drafting unit of this standard: Shenyang Blower Research Institute The main drafters of this standard: Miao Liping, Chen Mingliang, Kong Guilan. 346
Mechanical Industry Standard of the People's Republic of China
Fan vibration detection and its limied value
Fan vibration detection and its limied value This standard specifies the vibration limit of fan operation. JB/T 8689-1998
This standard also specifies the measurement position for measuring fan vibration, the requirements for measuring instruments, the installation of the measured product and the operating conditions during measurement.
This standard applies to the factory inspection, type test and acceptance of vibration indicators of centrifugal, axial flow and mixed flow fans.
2 Definitions
This standard adopts the following definitions.
2.1 Root mean square value of vibration velocity
Root mean square value of vibration velocity is also called effective value of vibration velocity. For periodic vibration, it refers to the square root of the average value of the instantaneous value of vibration velocity in a vibration cycle. Its mathematical expression is as follows:
Wherein: Vrms—root mean square value of vibration velocity (effective value); V(t).
V2(t)dt (mm/s)
Function of vibration velocity changing with time t, mm/s; t—time independent variable, s;
T-—vibration period, s.
For sinusoidal vibration at a single frequency, V(t) = Vcoswt, then the root mean square value of the vibration velocity calculated by the above formula is: Vrms
Wherein: V single peak value of vibration velocity, mm/s; V=Xw
X-single peak value of vibration displacement, mm;
w-angular frequency, rad/s.
2.2 Periodic vibration
Vibration whose vibration waveform repeats itself after every time period T. Such as the vibration of a fan at a certain speed. 2.3 Rigid support
After the fan is installed, the basic natural frequency of the "fan-support system" is higher than the main working frequency of the fan, which is called rigid support. For example, a general fan is directly and firmly connected to a hard foundation. 2.4 Flexible support
After the fan is installed, the basic natural frequency of the "fan-support system" is lower than the main working frequency of the fan, which is called flexible support. For example, the Ministry of Machinery Industry of the People's Republic of China approved on March 19, 1998 and implemented on July 1, 1998
JB/T8689-1998
Under special conditions, the fan is connected to the foundation through a vibration isolator. 3 Requirements
3.1 Measurement parameters and their limits
3.1.1 The measurement parameter is the root mean square value of the moving speed (Vrms), which can be directly measured and displayed by an instrument with effective value detection characteristics. 3.1.2 In each measurement direction and measurement point specified in 3.2, the measured root mean square value of the vibration velocity should not exceed the following provisions: rigid support: Vrms≤4.6mm/s,
flexible support: Vms≤7.1mm/s.
3.2 Measurement location
3.2.1 For fans whose impellers are directly mounted on the motor shaft, the vibration values ​​in the vertical, horizontal and axial directions should be measured at the bearings at both ends of the motor stator (see Figure 1). When the motor is equipped with a fan cover, the axial vibration may not be measured. Vertical
Horizontal direction
3.2.2 For fans with two bearing bodies in double bearings, measure the vibration values ​​of each bearing in the three directions shown in Figure 2. Vertical
Horizontal direction
When both bearings are installed in the same bearing box, measure the vibration values ​​at the bearing part of the bearing box according to the requirements shown in Figure 3. 3.2. 3
Note: → and × in the figure are the direction and position of the measuring point. Figure 3
Yongping direction
3.2.4 When the bearing box to be measured is inside the fan housing, according to the requirements of 3.2.2 or 3.2.3, a vibration sensor shall be pre-installed, and then it shall be led out of the fan and connected to the indicator to measure its vibration value. The deviation between the installation direction of the sensor and the measurement direction shall not exceed ±5°. 3.2.5 When the bearing box to be measured is inside the fan housing and the vibration sensor cannot be preset, the vibration values ​​in the vertical and horizontal directions can be measured at the corresponding parts of the fan housing 348
JB/T8689-1998
at the support bearing, as shown in Figure 4. Vertical
Horizontal direction
3.3 Measuring instrument
3.3.1 The measuring instrument shall have the effective value detection feature and can directly display the root mean square value of the vibration velocity. When such an instrument is not available, Appendix A (the appendix of the prompt) may be referred to with the consent of the user. 3.3.2 The frequency range of the measuring instrument should generally be 10 to 1000Hz. The main working frequency of a few fans is lower than 10Hz. In this case, more specialized measuring instruments should be used, and the frequency range of the instrument must include the frequency at the working speed of the fan. 3.3.3 The measurement error of the measuring instrument should not be greater than ±10% of the indicated value. 3.3.4 The measuring instrument must be qualified by the metrology department before it can be used. 3.4 Installation of the measured fan
3.4.1 During the factory inspection, the measured fan should be directly fastened to a solid test bench base to achieve rigid support. 3.4.2 During the on-site acceptance, the measured fan should be installed completely according to the actual use, which can be rigid support or flexible support. 3.5 Operating conditions of the measured fan
3.5.1 The fan should operate at a stable rated speed and rated operating conditions. If the fan has multiple rated speeds and rated operating conditions, the vibration under various rated conditions should be measured separately. The largest value shall be taken to represent the vibration value of the fan, and the operating conditions during the measurement shall be noted.
3.5.2 If the fan cannot achieve the rated speed and rated operating conditions at the same time when being tested due to objective conditions, the vibration value shall be measured as close to the rated operating conditions as possible at the rated speed, and the operating conditions during the measurement shall be recorded. 3.5.3 If the fan adopts a variable speed regulator to adjust the use range, the vibration values ​​at high, medium and low speeds shall be measured separately within the speed adjustment range specified by the fan, and each speed shall be as close to the use conditions as possible. The largest measured value shall be taken to represent the vibration value of the fan, and the operating conditions during the measurement shall be noted. 3.5.4 If the fan cannot meet the actual hot operating conditions when being tested, it can be operated in a cold state, taking the conditions closest to the rated operating conditions allowed by its motor, and the operating conditions during the measurement shall be noted. 3.5.5 The difference between the vibration value when the fan is running and when it is not running must be greater than three times when the fan is not running, otherwise it is considered that the fan is in an external vibration environment and measures should be taken to avoid external influences. 3.5.6 The temperature, humidity, magnetic field, corrosion characteristics, etc. around the fan should meet the requirements for instrument use. 349
JB/T86891998
Appendix A
(Suggested Appendix)
Vibration velocity and vibration displacement limits
If the existing vibration measuring instrument does not have the effective value detection function, the vibration velocity (peak value) or vibration displacement (peak value) can be measured with the user's consent. Their limits are shown in Table A1.
Support type
Rigid support
Flexible support
Vibration velocity (peak value) V
Note: n is the working speed of the fan (r/min). 350
Vibration displacement (peak-to-peak value) XWww.bzxZ.net
≤1.24×105/m
≤1.9×105/n
Approximate corresponding dynamic velocity effective value m
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