1、BRITISH STANDARD BS 6841:1987 Guide to Measurement and evaluation of human exposure to whole-body mechanical vibration and repeated shock UDC 614.872.5:53.08BS6841:1987 This British Standard, having been prepared under the directionof the General Mechanical Engineering Standards Committee, was publi
2、shed under the authority ofthe Board of BSI and comes into effect on 30September1987 BSI 08-1999 The following BSI references relate to a the work on this standard: Committee reference GME/21 Draft for comment86/71027 DC ISBN 0 580 16049 1 Co-operating organizations The preparation of this British S
3、tandard was entrusted by the General Mechanical Engineering Standards Committee (GME/-) to Technical Committee GME/21, upon which the following bodies were represented: British Engine Group of SMMT British Maritime Technology British Steel Corporation Department of Trade and Industry (National Engin
4、eering Laboratory) Electricity Supply Industry in England and Wales Institute of Sound and Vibration Research Institution of Electronic and Radio Engineers Institution of Mechanical Engineers Lloyds Register of Shipping Ministry of Defence Motor Industry Research Association Power Generation Associa
5、tion (BEAMA Ltd.) Society of British Aerospace Companies Ltd. Society of Environmental Engineers United Kingdom Atomic Energy Authority The following bodies were also represented in the drafting of the standard, through subcommittees and panels: AFRC Institute of Engineering Research British Aggrega
6、te Construction Materials Industries British Agricultural and Garden Machinery Association Ltd. British Railways Board Department of the Environment (Building Research Establishment) Ergonomics society Forestry Commission Health and Safety Executive Heriot-Watt University Institute of Explosives Eng
7、ineers Institution of Civil Engineers London Regional Transport Medical Research Council Power Saw Association of Great Britain Society of Motor Manufacturers and Traders Limited University College of Wales Amendments issued since publication Amd. No. Date of issue CommentsBS6841:1987 BSI 08-1999 i
8、Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Effects of whole-body vibration and repeated shock 1 3 Vibration measurement and frequency weighting 3 4 Guide to the evaluation of vibration and repeated shock with respect to effects on health 8 5 Guide to the eval
9、uation of vibration with respect to effects on human activities 10 6 Guide to the evaluation of vibration and repeated shock with respect to discomfort and perception 12 7 Guide to the evaluation of low frequency vibration with respect to the incidence of motion sickness 14 Appendix A Effects of vib
10、ration and repeated shock on health 16 Appendix B Effects of vibration on human activities 19 Appendix C Effects of vibration and repeated shock on comfort and perception 20 Appendix D Effects of whole-body low frequency vibration on theincidenceofmotion sickness 22 Figure 1 Basicentric axes of the
11、human body 4 Figure 2 Moduli of the frequency weightings with band-limiting filters 9 Figure 3 Root-mean-square acceleration magnitudes corresponding tovibration dose values from1.9ms 1.75toms 1.75for vibration exposureperiods from1s to24h 17 Table 1 Outline guide to the application of frequency wei
12、ghtings 5 Table 2 Characteristics of band-limiting and band-pass filters for frequencyweightings 6 Table 3 Asymptotic approximations to the frequency weightings giveninTable 2 7 Publications referred to Inside back coverBS6841:1987 ii BSI 08-1999 Foreword BS6841 was prepared under the direction of t
13、he General Mechanical Engineering Standards Committee. It replaces Draft for Development DD32:1974, which is therefore withdrawn. ISO2631:1985, being broadly similar to DD32:1974, suffers similar limitations in that it does not define an adequate or reasonable procedure for measuring vibration expos
14、ures and specifies vibration limits which are not generally accepted. Growing international recognition of these problems lead to commencement of work on a revision of the International Standard during1979. International agreement on the revision of ISO2631 is not yet complete. The principal differe
15、nces between BS6841 and DD32 (and, therefore, between BS6841 and ISO2631:1985) are the provision of greater guidance on vibration effects without defining vibration limits, the elimination of the concept of fatigue-decreased proficiency, the inclusion of a simple time-dependency and a method of asse
16、ssing repeated shocks and intermittent vibration (i.e.the vibration dose value), the modification and more complete definition of necessary frequency weightings, the definition of a standard means of assessing the discomfort caused by rotational vibration on the seat and translational vibration at t
17、he feet and seat back of seated persons, and the inclusion of more quantitative guidance on motion sickness (i.e.the motion sickness dose value). A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct ap
18、plication. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 24, an inside back cover and a back cover. This standard has been updated (see copyright d
19、ate) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6841:1987 BSI 08-1999 1 1 Scope Transport (air, land and water), machinery (e.g.in industry and agriculture) and industrial activities (such as piling and blasting) expose the hum
20、an body to mechanical vibration and repeated shock. This British Standard guide gives methods for quantifying vibration and repeated shocks in relation to human health, interference with activities, discomfort, the probability of vibration perception and the incidence of motion sickness. The guide i
21、s applicable to motions transmitted to the body as a whole through the supporting surfaces: the feet of a standing person, the buttocks, back and feet of a seated person or the supporting area of a recumbent person. Vibration is often complex, containing many frequencies, occurring in several direct
22、ions and changing over time. Vibration limits are not presented. However, the methods have been given so that they may be used as the basis of limits which may be prepared separately. Various appendices provide current information on the possible effects of vibration. The guidance is intended to be
23、a fair compromise based on the available data and should satisfy the need for recommendations which are simple and suitable for general applications. The guidance is presented in numerical terms to avoid ambiguity and to encourage precise measurements. When using the recommendations it is important
24、to bear in mind the restrictions placed on their application. More precise information may sometimes be obtained from the scientific literature. NOTEThe titles of the publications referred to in this standard are given on the inside back cover. 2 Effects of whole-body vibration and repeated shock 2.
25、1 General Exposure to whole-body vibration causes a complex distribution of oscillatory motions and forces within the body. This may cause unpleasant sensations giving rise to discomfort or annoyance, result in impaired performance (e.g.degraded vision) or present a health risk (e.g.tissue damage or
26、 deleterious physiological change). There are many factors which influence human response to vibration. The variables include the following. Intrinsic variables Population type (age, sex, size, fitness, etc.) Experience, expectation, arousal, motivation, financial involvement Body posture Activities
27、 Extrinsic variables Vibration magnitude Vibration frequency Vibration axis Vibration input position Vibration duration Seating, restraints, etc. Other environmental influences (noise, heat, acceleration, light) The four principal effects of vibration are considered to be: a) degraded health; b) imp
28、aired activities; c) impaired comfort; d) motion sickness.BS6841:1987 2 BSI 08-1999 2.2 Effects on health Any part of the body may be injured by exposure to a sufficient magnitude of vibration. The parts of the body most likely to be injured during exposure to whole-body vibration will depend on the
29、 distribution of motion within the body and this will depend on the vibration frequency and axis and the coupling of the body to the vibrating source. The probabilities and extents of particular health effects from prolonged exposures to whole-body vibration have not been established. There is a sho
30、rtage of conclusive evidence relating specific injuries to definite causes. Therefore, it is not yet possible to provide a definitive dose-effect relationship between whole-body vibration and injury or health damage. Biodynamic models and a knowledge of the physical properties of body tissue may be
31、used to predict injury. Subjective data concerning vibration magnitudes which cause discomfort and pain may give some indication of the possibility of injury for various conditions, although it is recognised that sensations may not necessarily correlate with pathological damage. In this standard, da
32、ta from all of the above methods have been used to provide the best possible general guidance on methods of assessing vibration and shock with respect to impaired health. NOTEEpidemiological studies suggest that back complaints are associated with exposure to prolonged periods of vibration and repea
33、ted shock but there are currently inadequate data to define a precise dose-effect relationship. Similarly, it is not yet possible to provide a definitive dose-effect relationship between whole-body vibration and any other injury. 2.3 Effects on activities Vibration of the body may affect: a) the acq
34、uisition of information via the senses; b) information processing; c) levels of arousal, motivation or fatigue; d) intentional actions. Vision is the perceptual mechanism most easily affected by vibration since even small movements of an image on the retina of the eye can degrade visual acuity. Ther
35、e is some evidence that the senses of touch and hearing may also be influenced by vibration but the effects are often small. The perception of body orientation and postural stability can also be affected by vibration. There is little evidence that whole-body vibration directly affects cognitive proc
36、esses. It is often difficult to separate direct effects from those caused by changes in arousal or motivation. Arousal, motivation and fatigue are aspects of the behavioural state of an individual and, although they are not readily quantifiable, their effects can be very great. Vibration has been ob
37、served both to improve and to reduce task performance. This may be because it fatigues or arouses or, because of increased task difficulty, motivates. At present, these effects of vibration cannot be reliably predicted and are not quantified in this standard. Actions performed by a person are often
38、accomplished by speech or movements of the hands or feet. Whole-body vibration may cause a modulation of speech but under normal listening conditions this does not degrade intelligibility. Where an activity requires fine movements of the limbs, whole-body vibration can have a large effect on profici
39、ency. Tasks involving gross locomotor movements, or lifting or carrying, are most likely to be affected by low frequency vibration. The precise effects of vibration on task performance are highly dependent on the task characteristics: detailed guidance cannot be provided in this standard. 2.4 Effect
40、s on comfort The complex distribution of oscillatory motion and force within the body during whole-body vibration produces complex sensations. The location and character of the sensations vary greatly according to the vibration frequency, axis and other factors. In this standard the term “discomfort
41、” is applied to the sensations arising directly from the vibration. A wider term is sometimes used in transportation systems to include reactions to other aspects of the environment (e.g.noise) and the effects of motion on common activities (e.g.reading and writing). In this standard a method is def
42、ined to enable the discomfort of two or more complex vibrations to be compared. Whether a degree of discomfort is acceptable will depend on many factors. A limiting value should be selected by the user for specific applications: different limits for discomfort will apply in different circumstances.B
43、S6841:1987 BSI 08-1999 3 For some applications, knowledge of whether vibration can be perceived is useful. This standard therefore also defines the probability of perceiving low magnitudes of whole-body vibration. NOTEAlthough pleasurable sensations may be experienced with some types of oscillatory
44、motion they are outside the scope of this standard and they will not usually be confused with those causing discomfort. 2.5 Motion sickness Low frequency (less than about0.5Hz) oscillation of the body can cause the motion sickness syndrome characterized principally by pallor, sweating, nausea and vo
45、miting. Although other types of stimulation may cause similar symptoms, this standard is solely concerned with kinetosis (i.e.motion sickness) due to low frequency vertical z-axis oscillation of the human body. The guidance is formulated so as to enable the probability of vomiting in a given populat
46、ion to be predicted. 3 Vibration measurement and frequency weighting 3.1 Units of vibration magnitude The primary quantity for expressing vibration magnitude is the weighted root-mean-square acceleration inms 2for translational vibration and rad s 2for rotational vibration. Root-mean-square (r.m.s.)
47、 measures of acceleration may be used when the crest factor does not exceed6.0. However the severity of motions which are intermittent or contain occasional high peak values and have crest factors in excess of6.0 will often by underestimated byr.m.s. measures. This standard gives alternative methods
48、 for the evaluation of these motions. NOTEThe crest factor of the motion is to be determined from the peak andr.m.s. value of the acceleration after it has been frequency weighted by the appropriate frequency weighting network. Crest factor = (weighted peak acceleration)/(weighted r.m.s. acceleratio
49、n). The peak andr.m.s. values are to be determined over the full period of vibration exposure which it is desired to assess. 3.2 Direction of measurement Vibration should be measured according to a coordinate system centred at the interface with the body. The principal relevant basicentric systems are shown in Figure 1. In many situations it is not feasible to obtain precise alignment of vibration transducers with the preferred basicentric axes. The sensitive axes of transducers may deviate from the preferred axes by up to20 degrees where necessary. Where a pe
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