1、BRITISH STANDARD BS 7085:1989 Guide to Safety aspects of experiments in which people are exposed to mechanical vibration and shock UDC 614.872.5BS7085:1989 This British Standard, having been prepared under the directionof the General Mechanical Engineering Standards Policy Committee, waspublished un
2、der the authorityof the Board of BSIandcomes into effect on 31August1989 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference GME/21 Draft for comment 87/74731 DC ISBN 0 580 17175 2 Committees responsible for this British Standard The preparation of this
3、British Standard was entrusted by the General Mechanical Engineering Standards Policy Committee (GME/-) to Technical Committee GME/21, upon which the following bodies were represented: British Maritime Technology British Steel Corporation Electricity Supply Industry in England and Wales Institute of
4、 Sound NOTESee Appendix A of BS6841:1987. b) the extraneous risk that malfunction or inadvertent operation of the equipment used to generate the mechanical vibration or shock may cause the subject to be exposed unintentionally to motions so severe as to cause injury or ill-health; c) the risk of inj
5、ury to the subject, the experimenter, or others in the vicinity arising from any of the following: 1) the relative motion between the vibration equipment and its surroundings; 2) mechanical or other failures; 3) falling. 3.2 Inherent risks in mechanical vibration and shock experiments The inherent r
6、isk that exposure of a subject to mechanical vibration or shock may lead to injury or ill health depends on the following two possible causes: a) using mechanical vibration or shock that is too severe in terms of magnitude or duration; NOTEInformation about magnitudes of mechanical vibration or shoc
7、k is given in3.3. b) failure to exclude from the test a subject who is medically unfit or otherwise particularly sensitive to mechanical vibration or shock. NOTEPrecautions to be taken with subjects are given in clause8. 1) Hereinafter referred to as “the subject”.BS7085:1989 2 BSI 11-1999 3.3 Sever
8、ity of mechanical vibration or shock stimulus The effects on subjects of mechanical vibration and shock depend on the magnitude, frequency content, direction of action and duration of the stimuli, all of which should be included in assessing the severity. In all cases the mechanical vibration is to
9、be measured at the interface of the subject with the vibrating surface in accordance with BS6841. Vibrations may be characterized as periodic or random and for the purpose of this standard are restricted to frequencies between0.5Hz and80Hz. Shocks may be applied with or without the presence of vibra
10、tion, with various characteristics and may be applied singly or repetitively. Figure 1 Basicentric axes of the human bodyBS7085:1989 BSI 11-1999 3 Mechanical vibration and shock should be characterized from measurements of acceleration in three mutually perpendicular axes, with the addition of a fou
11、rth measurement, for seated subjects, of the fore-and-aft (x-axis) acceleration at the interface with the backrest in accordance withA.5 of BS6841:1987 (seeFigure 1). Frequency weighting functions which reflect the different sensitivities of subjects to vibration stimuli with different axes are give
12、n inAppendix A. The use of these weighting functions enables exposure to continuous sinusoidal or random mechanical vibration, which is statistically stationary, to be assessed simply in terms of the r.m.s.value of frequency-weighted acceleration and its duration. Exposure to mechanical vibration, w
13、hose characteristics vary with time, and to mechanical shock, may be assessed in terms of a vibration dose value VDV (in ms 1.75 ) which is calculated from the following equation: where For mechanical vibrations which are statistically stationary the estimated vibration dose value eVDV (in ms 1.75 )
14、 may be approximated from the following equation (seeA.4 of BS6841:1987): where For mechanical vibration which comprises significant components in more than one direction, a total vibration dose value can be calculated as the fourth root of the sum of the fourth powers of vibration dose values in ea
15、ch axis. Alternatively, where r.m.s.values have been calculated, a convenient approximation to the total vibration magnitude may be determined as the square root of the sums of the squares of the individual ponents (seeTable 1). 3.4 Extraneous risks in mechanical vibration and shock experiments 3.4.
16、1 Equipment malfunction. Many vibrating devices used in experiments have a large quantity of available or stored energy. An inherent problem in the design of vibration systems is that the subject may be exposed to unexpected or frightening transients, or at worst, to potentially dangerous magnitudes
17、 of mechanical vibration or shock as a result of a malfunction. In shock experiments, the subject is either brought suddenly to rest after slow acceleration to a specified velocity, or accelerated suddenly from rest. There is an attendant risk that equipment malfunction could lead to dangerous magni
18、tudes of shock. Equipment design should be such that, in the event of malfunction or emergency stop procedures, the subject should not be exposed to changes in the force environment of hazardous intensity or duration. Equipment should be designed so that no failure could result in magnitudes of mech
19、anical vibration or shock producing vibration dose values in excess of15ms 1.75 , unless the experiment is designed to study the effects of higher magnitudes. For such experiments, the magnitude during failure conditions should be only slightly in excess of those being studied. 3.4.2 Physical contac
20、t with moving parts. Mechanical vibration and shock experiments present the following three particular physical hazards: a) the experimenter or another person in the vicinity of the equipment may receive a blow through inadvertent contact with the moving parts; b) the subject on a moving part may re
21、ceive a blow through inadvertent contact with a fixed object; c) anyone on the equipment or in the vicinity may be at risk from pinching or shearing between fixed and moving parts. NOTEThe principles of machinery safeguarding are covered in BS5304. 3.4.3 Subjects restraint. In experiments where subj
22、ects are restrained, special care should be taken to ensure that during normal operation or malfunction any restraint does not present a hazard. Table 1 Weighted acceleration equivalent to a vibration dose value of15ms 1.75for continuous mechanical vibration at constant magnitude a (t)is the frequen
23、cy-weighted acceleration (inms 2 ); T is the total period of exposure (in s). a is the r.m.s.value (in ms 2 ); t o is the duration (in s). Duration of exposure 1 s 4 s 16 s 1 min 4 min 16 min 1 h 4 h 8 h Weighted acceleration, r.m.s (in ms 2 ) 10.71 7.57 5.36 3.84 2.72 1.92 1.38 0.98 0.82BS7085:1989
24、 4 BSI 11-1999 4 Operational vibration dose values 4.1 General The recommendations in this standard provide for two categories of experiment which are differentiated according to whether or not a medical officer should be in attendance. The decision is based on an assessment of the degree of severit
25、y of mechanical vibration or shock to which subjects are to be exposed. 4.2 Experiments not requiring a medical officer to be in attendance The attendance of a medical officer is not essential for experiments in which the subjects are exposed to magnitudes of mechanical vibration and shock comparabl
26、e to those found in common forms of transportation and in any but the most severe of civilian working environments. These are defined as experiments in which the total daily exposure for any subject does not exceed a vibration dose value of15ms 1.75 . For continuous mechanical vibration at a constan
27、t magnitude this is equivalent to r.m.s.values of frequency weighted acceleration for different durations of exposure as shown inTable 1. 4.3 Experiments requiring a medical officer to be in attendance For experiments in which any subject is exposed to mechanical vibration or shock whose vibration d
28、ose value exceeds15ms 1.75it is recommended that a medical officer should be in attendance (see6.2.3). If the exposure is likely to approach or exceed a severity twice as great as that at which a medical officer should be in attendance (i.e.vibration dose value greater than 30ms 1.75 ), prior advice
29、 from a relevant medical specialist should be sought on the inherent risk of the experiment and on the criteria for the selection of subjects. 5 Design of equipment 5.1 General The equipment should be designed and constructed so that under normal operation the motion stimulus can be controlled by th
30、e operator and that the magnitudes of mechanical vibration or shock do not exceed the expected values. Other than as indicated in4.3, the subject should not be exposed to sustained or transient acceleration whose total vibration dose value exceeds15ms 1.75in the event of the failure of any of the fo
31、llowing: a) the operator; b) electrical or mechanical components of the device; c) the power supplies to the device; d) the software in programmable systems. In order to ensure safe operation, the designer of the equipment should pay particular attention to the following features. 1) Mechanical and
32、electrical components should be chosen for high reliability and should be conservatively rated. The electrical design and construction of equipment should be in accordance with BS2771-1. 2) Moving parts should be adequately guarded in order to protect the subject, the operator and any observer in th
33、e vicinity of the machine. Where appropriate, protection should be in accordance with BS5304. 3) The subject should be adequately restrained, particularly where malfunction would jeopardize the safety of an unrestrained subject. 4) The device and any electrical equipment used in conjunction with the
34、 machine should be adequately earthed so that the subject and operator are protected from electric shock. 5) Emergency stop and shut-down procedures should render the device safe so that the subject can escape from the equipment with the minimum delay in the event of an emergency. 6) Safety and cont
35、rol wires and fluid power lines should be positioned and secured in such a manner that accidental disconnection or breakage does not occur. In addition to these general design features, points relating to the operational controls and displays, the control and associated limit circuits, end of stroke
36、 snubbing and test facilities are dealt with in5.2 to5.6. However, this list covers only features which experience has shown to be important for particular systems (mainly electro-hydraulic). It is the duty of the system designer to examine a particular system and attempt to predict and combat all p
37、ossible modes of failure. 5.2 Operator controls and displays 5.2.1 Due attention should be given to the ergonomics of operator controls and displays. 5.2.2 The start-up and shut-down procedures should follow a logical sequence and be sequence interlocked to prevent improper operation. 5.2.3 The oper
38、ator should be provided with displays which unambiguously indicate the following: a) the status of the safety circuits and the nature of a malfunction if this is detected by a safety circuit; b) when the device is in a safe mode (e.g.when the actuator is not energized or is physically locked) in order that the subject may safely be positioned on, or leave, the motion platform;
