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The Impact of Vibrations Upon the MusculoSkeletal System

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1 transducer 8 ponderation in frequency (including band limitation) ... 4 cable 11 time ponderation. 5 input electrical signal 12 additional processing ... – PowerPoint PPT presentation

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Title: The Impact of Vibrations Upon the MusculoSkeletal System


1
The Impact of Vibrations Upon the
Musculo-Skeletal System
  • Dipl. Eng. Silviu PLATON
  • Dipl. Eng. Dan NICULESCU
  • The National Research and Development Institute
    on Occupational Safety

2
1. The vibrations. Risk factor for health and
safety
  • Vibration or oscillation the movement of a
    system as compared to its reference condition
  • Characteristic parameters
  • Acceleration level (efficient values),
  • Frequency content (spectral analysis),
  • Contact point of the human body with the
    vibration source (global vibrations, forearm
    hand vibrations),
  • Exposure duration.

3
  • The human body is submitted to the action of
    vibrations when
  • the machines it travels with are concomitantly
    vibrating,
  • the person concerned is to be found in rooms
    where machines and installations are operating,
  • Upon certain parts of the human body i.e.
    muscles, bones, articulations, there are directly
    acting those vibrations arising from vibrating
    machines, various pneumatic tools etc.

4
  • The vibrations acting upon the human body may
    induce
  • Disturbance of the physical and intellectual
    activity tiredness,
  • Mechanical damages fractures arise at certain
    levels of acceleration, lung damages, heart
    damages,
  • Subjective phenomena lack of comfort, pain and
    anxiety,
  • Generally, three steps of evaluating the
    vibrations effect are considered e.g.
    perception, discomfort and intolerance threshold.

5
2.Global vibrations, forearm - hand vibrations.
Effects upon the human body
  • GLOBAL VIBRATIONS
  • The exposure to global vibrations induces a
    complex distribution of the oscillating forces
    and movements into the body,
  • The location and the nature of the sensations may
    vary to a significant extent depending on the
    vibrations frequency, direction, etc.,
  • The global vibrations transmitted to the whole
    body may affect
  • Acummulation of information through the senses,
  • Information processing
  • Levels of interest, stimulation or tiredness,
  • deliberate actions.

6
  • The sight represents the perception mechanism
    that may be easily influenced by the vibrations
    action as the visual acuity may be damaged even
    for unsignificant movements of an image on the
    eye retina,
  • The perception in terms of body orientation and
    position stability may be also affected.
  • For the individual exposed to the vibrations
    action within the work system, a significant
    importance shall be given to the body contact
    point with the vibrations source.

7
Acting directions of the mechanical vibrations
transmitted to the whole body through the
supporting area
8
FOREARM HAND VIBRATIONS
  • The severity of the biological effects of the
    vibrations transmitted to the forearm- hand
    system, in working conditions, is influenced by
    several factors
  • Exposure duration and working method
  • Duration of working day exposure and cumulative
    duration per working day
  • Direction of the vibration transmitted to the
    hand as well as the extent and direction of the
    forces applied by the operator through his hands
    to the tool and the body during the exposure i.e.
    articulations angles of the fingers, hand, fist,
    elbow and shoulder.

9
  • The surface and the part of the hands/arms
    exposed to vibrations,
  • The type and condition of the vibrating
    mechanisms, of the manual tools or processed
    piece,
  • The operators working method and qualification
    factors that should be considered,
  • Factors related to the working environment -
    microclimate, noise and chemical agents,
  • Raynaud syndrome usually associated to the
    vibrations action upon the arm hand system
    being also involved in other general or
    occupational diseases.

10
2.1 Effects of the vibrations action
transmitted to the musculo-skeletal system
  • The injuries induced by mechanical vibrations
    upon the musculo-skeletal system as occupational
    disease represent one of the oldest occupational
    disease that need surgical treatment,
  • They may be generated by working with vibrating
    tools, these vibrations acting upon the
    extremities,
  • The consequences of the vibrations appear within
    muscles, articulations and bones that are
    actively participating in carrying out
  • pushing onto the tools and reception of
    the vibrations,

11
  • In some cases, diseases related to the elbow,
    fist and shoulder articulation are reported
    corresponding to the clinical image of a
    deforming arthrose that should be considered as
    being amplified and premature as compared to the
    normal evolution in age,
  • The most solicited is the cubitus humeral
    articulation followed by the fist articulation
    and the scapulo- humeral articulation
    respectively.

12
  • Circulatory diseases one of the very first
    issues that should be considered when speaking of
    negative effects as a result of the activities
    carried out by means of vibrating tools,
  • Circulatory troubles are manifested through the
    occurrence of vascular spasms at finger level
    immediately followed by skin cyanosis or
    tumefaction,
  • The circulatory troubles appear independently of
    the fact that the person exposed to vibrations
    works within a warm or cold microclimate.

13
3. Basic health and safety requirements related
to the exposure of workers to the vibrations
generated risks
  • HG 1876-2005
  • 3.1 Limit values of exposure and exposure values
    beyond which the action starts
  • 3.1.1 For the vibrations transmitted to the arm
    hand system
  • - the limit value of daily occupational
    exposure calculated for a reference period of 8
    hrs is 5 m/s2
  • - the value of the daily exposure beyond which
    the action starts, calculated for a reference
    period of 8 hrs is 2.5 m/s2.

14
  • 3.1.2 For the vibrations transmitted to the whole
    body
  • -the limit value of daily occupational
    exposure calculated for a reference period of 8
    hrs should be 1.15 m/s2,
  • - the value of the daily exposure for which the
    action starts, calculated for a reference period
    of 8 hrs should be 0.5 m/s2

15
Employers obligations
  • Establishing and assessment of risks the
    employer shall evaluate the necessity of
    measuring the risks arising from the exposure to
    vibrations,
  • Employers information and training,
  • Employers consultation and participation,
  • Health surveillance.
  • HG 1876 transposed Directive 44-2003 of EU

16
4. Methods of determination and apparatus
  • SR ISO 2631/11997 for the determination of
    global vibrations
  • - evaluation of the exposure level to
    vibrations is based on the calculation of the
    daily exposure expressed as continuous
    acceleration equivalent for a reference period of
    8 hrs. It is calculated as the highest value
    (rms) of ponderated accelerations in frequency as
    determined on three orthogonal axis, for a
    sitting or standing worker.

17
SR ISO 53491995 for the determination of the
arm hand vibratations
  • - the evaluation of the exposure level to
    vibrations transmitted through the arm hand
    system is based on the calculation of the daily
    exposure value for a reference period of 8 hrs
    expressed as the average square root (rms) (total
    value) of the ponderated acceleration values in
    frequency as determined versus three orthogonal
    axis z, x, y
  • - in case of the equipment that are to be be hold
    by both hands, the measurements should made for
    each hand. The exposure shall be determined
    depending on the highest value of the two values
    found.

18
Fig. 4.1 Examples of practical measurement
positions for several currently used tools
19
SR EN ISO 8041-2006 Operational diagram of an
apparatus or system for the measurement of
vibrations
Legend 1 transducer 8 ponderation
in frequency (including band limitation) 2
mounting system 9 band limited
output signal 3 vibrating surface 10
ponderated output signal in frequency 4
cable 11 time ponderation 5 input
electrical signal 12 additional
processing 6 signal conditioning 13
display 7 band limitation
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