Allowable vibration value of equipment in production operation area - national standard allowable value
From the perspective of physics and physiology, the human body is a complex system. If human is regarded as a mechanical system, it contains a number of linear and nonlinear "components", and the mechanical properties are very unstable. People have great differences in height, weight, bones, muscles and other aspects, especially when it comes to psychological effects, the situation is more complicated. According to the frequency range, vibration is divided into low frequency vibration (below 30Hz), medium frequency vibration (30 ~ 100Hz) and high frequency vibration (above 100Hz). The human can feel the vibration frequency range is 1 ~ 100Hz. Experiments show that people are most sensitive to vibration sensation with a frequency of 2-12Hz, and the sensitivity decreases gradually when the frequency is higher than 12Hz or lower than 2Hz. The most harmful vibration frequencies to the human body are those that coincide with the natural frequencies of certain organs of the human body (i.e. resonate). These natural frequencies are around 6Hz for the human body, 8Hz for the internal organs, 25Hz for the head, and 250Hz for the nervous center.
The impact of vibration on the human body can be divided into whole body vibration and local vibration. Whole body vibration refers to the vibration of a person directly located on a vibrating object; Local vibration refers to the local vibration of the human body caused by shaking objects in the hand. The vibration people feel in the production operation area is the whole body vibration. The International Organization for Standardization (ISO) published recommendations in 1978 (ISO2631), the standard for human exposure in the vibration environment. The effect of vibration on the human body depends on four parameters: vibration intensity, frequency, direction, and exposure time. When the operator in the production operation area is subjected to whole-body vibration, the control limits should be divided into comfort reduction limits, proficiency reduction limits and exposure limits according to vibration intensity, frequency, direction and duration. In the vibration operating environment, when the vibration value exceeds a certain limit value, the attention will be diverted and the work efficiency will be reduced. On the basis of the comfort reduction, the limit of proficiency reduction is calculated by multiplying the acceleration by 3.15 (acceleration level plus 10dB). When the vibration value is greater than this limit value, obvious fatigue and decreased workefficiency appear. Through vibration frequency spectrum analysis, acceleration values corresponding to each 1/3 frequency band at different vibration time and direction can be obtained. If any of these corresponding values exceed the values in the table, it is considered that the vibration environment exceeds the proficiency of human body and reduces the tolerance standard for vibration. Proficiency limit values shall be adopted in the design, and proficiency reduction limits in vertical and horizontal directions shall conform to the provisions of Table 4-4-1 and 4-4-2. Figure 4-4-1 and Figure 4-4-2 are applicable in the frequency range of 1 to 80Hz. As can be seen from the figure, for vertical vibration, people are most sensitive to the frequency range of 4 ~ 8Hz; For horizontal vibration, people are most sensitive to the frequency range of 1 ~ 2Hz. Vibration below 1Hz will appear in many forms of transmission and produce some effects completely different from higher frequencies, such as motion dizziness, etc. These effects cannot be explained simply by the intensity, frequency, and duration of the vibrations. Different people will have quite different reactions to vibrations below 1Hz, which is related to environmental factors and personal experience. For 8-hour exposure, the longitudinal vibration limits for severe discomfort are: frequency range 0.1 to 0.3Hz, acceleration 0.2m/s2; The frequency range is 0.3 ~ 0.6Hz, and the acceleration increases to 0.6m/s2. At 2 h exposure, the acceleration increases to 0.5m/s2 and 1.5m/s2, respectively, in the above two frequency ranges. At 5min exposure, the above accelerations rise to 1.1m/s2 and 3.3m/s2, respectively. 0.1 ~ 0.6Hz is the range of motion sickness. The sensation and influence of vibration higher than 80Hz mainly depend on the local conditions of the point of application. At present, there is no established standard of human overall vibration above 80Hz. The production operation area refers to the floor directly bearing the power equipment and the ground near the power equipment foundation. The vibration tolerance standard in the production operation area shall be determined on the basis that the health of the operator will not be damaged and the normal work will not be affected. When the operator is subjected to constant intensity steady-state vibration for 8 consecutive hours, the allowable vibration velocity in the operating area should be adopted according to Table 4-4-3. Table 4-4-3 Allowable vibration values from "Vibration Calculation and vibration Isolation Design Rules for load-bearing Structures of Buildings under Machine Dynamic Load"
Vibration tolerance standards for Possible Damage to buildings Vibrations generated by mechanical equipment and vehicles may cause damage to buildings, such as peeling of paint layers or cracking of filling walls. Generally, these vibrations will not endanger the safety of buildings. The physical quantities affecting building damage mainly include vibration velocity and vibration frequency. Engineering practice has proved that the damage degree of a building has a strong correlation with the peak vibration velocity. Germany, Britain and other national standards adopt the peak vibration velocity as the building damage control standard. Table 4-5-1 refers to the vibration velocity limits of DIN4150, Part III, issued in Germany in 1986 for the prevention of damage to buildings. The vibration speed of the building is lower than the limit value, usually no damage will occur; If the limit is slightly exceeded, the safety of the building will not be compromised, but may only result in non-structural damage (such as appearance cracks) and reduce the functioning of the building. The allowable values of vibration velocity for possible damage to the building can be adopted by referring to Table 4-5-1.
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