The Impact of Vibrations Upon the MusculoSkeletal System

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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

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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.

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• 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.

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• 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.

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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.

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• 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.

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Acting directions of the mechanical vibrations
transmitted to the whole body through the
supporting area
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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.

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• 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.

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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,

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• 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.

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• 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.

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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.

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• 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

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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

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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.

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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.

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Fig. 4.1 Examples of practical measurement
positions for several currently used tools
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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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