Sponsored Links
This presentation is the property of its rightful owner.
1 / 100

Vibration PowerPoint PPT Presentation

  • Uploaded on
  • Presentation posted in: General

Vibration. Sean Mahar, PhD, CIH, CSP, PE. Vibration Introduction. Types Problems Controls Measurements Standards. Sean Mahar. BS, Sacred Heart University MS, Texas A&M University PhD, University of Iowa Certified Industrial Hygienist Certified Safety Professional

Download Presentation


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Sean Mahar, PhD, CIH, CSP, PE

Vibration Introduction

  • Types

  • Problems

  • Controls

  • Measurements

  • Standards

Sean Mahar

  • BS, Sacred Heart University

  • MS, Texas A&M University

  • PhD, University of Iowa

  • Certified Industrial Hygienist

  • Certified Safety Professional

  • Professional Engineer


  • U of Wolverhampton, 4 years

  • Ohio University, 3 years

  • Worksafe Iowa, 3 years

  • US Navy, 9 years

  • Tracor, 1 year

Educational Objective

The student should have a basic understanding of the measurement and control of vibration, including what instruments are used, the relevant exposure limits, but they need not have the practical experience to enable them to carry out a vibrations survey.

Definitions and measurements units

Units of measurement - understanding of acceleration amplitude

Velocity amplitude displacement amplitude

Definitions and measurements units

Choice of measurement parameters, dynamic range and frequency information required

Relationship and implications of mass and stiffness and damping, natural frequency and static deflection

Monitoring instruments

Vibration transducers

Piezoelectric accelerometer. Also aware of existence of proximity probes and velocity pick-up.


Elements of a general purpose vibration meter.Also awareness of swept filter frequency analyser and fast Fourier transformanalyser.

Making a survey

ISO Evaluation of human exposure to whole body vibration:

  • Equivalent acceleration value

  • Frequencies of the vibration

  • Direction of excitement of the vibration

  • Time of exposure to vibration

Making a survey

ISO Guidelines for the assessment of human exposure to hand-arm vibration:

  • Frequency weighted RMS acceleration value

  • Probability of developing white finger syndrome

Exposure limits for vibration

  • ISO 2631:1997Guide for the eval. of human exposure to whole body vibration.

  • ISO 5349-1:2001 Guide to meas, and eval. of human exposure to vibration transmitted to the hand

  • HSG 88Hand -arm vibration

Control of vibration

Whole-body vibration damping

  • Use of suspension system for vehicles

  • Use of suspension system for seats of vehicles with stiff suspensions

  • Decrease operator's exposure time by job rotating

Control of vibration

Hand-arm vibration damping

  • Damping of tool internally

  • Insertion of damping between tool housing and hand

  • Remote operation of tool

  • Decreasing operator's exposure by job rotation

Vibration effects and limits

Health effects of whole body vibration, vibration dose

Sensitivity to vibration at different frequencies,

Fatigue - decreased proficiency and exposure limits, reduced comfort

Vibration effects and limits

Sources of vibration

Vibration in buildings,

Segmental vibration, hand arm vibration - neurological and vascular effects

Vibration from powered hand tools and other processes

Vibration effects and limits

8-hour energy equivalent weighted acceleration

Relationship between time to development of vascular symptoms and weighted vibration and exposure time

Vibration effects and limits

BSEN ISO 2631 4:2001

Fatigue - decreased proficiency and exposure limits, reduced comfort

BS 6472 1992

Vibration in buildings, 1-80 Hz


  • oscillatory motion of a system


  • oscillatory motion of a systemmotion - simple harmonic or otherwise system - gaseous, liquid, or solidair molecules vibrating 20 - 20,000 Hz is sound


Vibration Parameters

  • Displacement

  • Frequency

  • Velocity

  • Acceleration


x(t) = X sin (2 p t/T) = X sin w t

= X sin (2 p f t)

x = instantaneous displacement (m)

X = maximum displacement (m)

t = time (s),T = period of vibration (s)

f = frequency of vibration (Hz)

w = angular frequency (2 p f ) (radians/s)


v = dx/dt = wX cos (wt) =

= V cos (wT) = V sin (w + p/2)

= V cos (2 pf t)

v = instantaneous velocity (m/s)

V = maximum velocity (m/s)


a = dv/dt = d²x/dt² = - w²S sin (wt)

= - A sin (wt + p)

= - A sin (2 pf t)

a = instantaneous acceleration (m/s2)

A = maximum acceleration (m/s2)

Acceleration, rms

Acceleration, rms

Crest factor

Phase Difference

Non-harmonic motion

Non-harmonic motion

Effects depend on:

  • frequency (Hz)

  • displacement (m)

  • acceleration(m/s2) - a measure of the intensity

  • resonance - depends upon the natural resonant frequency of either the source of vibration or of the object being vibrated (the human body segments or organs).


Segmental or Hand-Arm Vibration

General or Whole Body Vibration

Segmental or Hand-Arm Vibration

Transmitted to hands

and arms from power

tools and other

vibrating equipment,

such as chain saws,

chipping tools, drills,

grinders, motor bikes.

General or Whole Body Vibration

Transmitted to the

sitting or standing body

through transmitting

surfaces such as in

aircraft, ships,

vehicles or working on

vibrating floors.

Segmental Vibration


  • finger blanching, particularly when exposed to the cold

  • tingling and loss of sensation in fingers

  • loss of light touch (difficulty fastening buttons and zippers)

  • pain and cold sensations between periodic white finger attack


  • loss of grip strength

  • bone cysts in fingers and wrists

  • carpal tunnel syndrome

Although segmental or local vibration almost always affects only upper limbs, legs can be affected if they come into contact with vibrating equipment.

Primary syndrome names

  • Raynaud's syndrome

  • Traumatic Vasospastic Disease

  • Vibration White Finger

  • Hand Arm Vibration Syndrome


  • sudden block in blood circulation to fingers

  • fingers become white, pale, cold, and sometimes painful

  • tactile sensitivity reduced

  • Symptoms last from minutes to hours, at first reversible


  • vascular disturbance

    • (changes in blood vessel walls)

  • nervous disturbance

    • (reflex contraction of smooth muscles of blood vessels)

  • occurs naturally in ~ 1% of pop, 90% of which are female


  • Physical

  • Biodynamic

  • Individual

Physical Factors

  • Dominant frequencies & vibration direction

  • Years of employment & daily duration

  • Temporal exposure pattern

  • Non-occupational exposure

Biodynamic Factors

  • Grip forces

  • Surface area & mass of hand

  • Handle orientation & texture

Individual Factors

  • Susceptibility

  • Vasoconstrictive agents

    • (smoking, drugs)

Frequency dependence

Taylor-Pelmear Classification

Taylor-Pelmear Classification

Taylor-Pelmear Classification

Taylor-Pelmear Classification

Taylor-Pelmear Classification

Stockholm scale for vascular symptoms

Stockholm scale for vascular symptoms

Stockholm scale for sensorineuralstages


Control Measures

  • Anti-vibration tools

  • Anti-vibration gloves

  • Safe work practices

  • Warm clothing, including gloves

  • Avoid holding the tool too tightly

Control Measures

  • Regular rest breaks

  • Rest the tool

  • Regular equipment maintenance

    • eg keeping cutting tools sharp

  • Reduce smoking

Whole Body Vibration

Whole Body Vibration

Vibration energy absorbed by body tissue and organs.

Whole Body Vibration

  • Spinal column disease

  • Digestive system problems

  • Cardiovascular effects

  • Motion sickness

  • Discomfort

  • Loss of balance and concentration

  • Fatigue

Whole Body Vibration

  • Energy absorbed by body tissue and organs muscles esp. important

  • Leads to

    voluntary/involuntary contraction causing fatigue esp. at resonant frequency

Whole Body Vibration

  • Reflex contractions reduce motor capabilities.increase risk of low back paineg- tractor, truck and bus drivers,

  • some studies have even shown radiographic changes

Whole Body Vibration

  • extremely strong vertical accelerations can cause spinal fractures (compression)


  • 5-10 Hz range: thoracic-abdominal system

  • 20-30 Hz range: head-neck-shoulder system

  • 60-90 Hz range: eyeball

Very low-frequency 0.1 - 1 Hz

  • Cause motion sickness by upsetting the body's balance mechanism.

  • Motion sickness appears to be worst at about 0.3 Hz

  • If pitch and roll are present as well as vertical displacement, tolerance to the vibration is lowered

Low-frequency 1 - 80 Hz

  • Short term (acute effects):

    • fatigue, insomnia, headache and "shakiness"

  • Long term (chronic effects):

    • circulatory, bowel, respiratory, muscular and back disorders

    • Vibration, lifestyle, and posture contribute

Frequency dependence


Control Measures

  • Move machine controls away from vibrating surfaces

  • Mechanically isolate the vibrating source

  • Maintain vibrating machinery

  • Reduce exposure time

    Much of these efforts will also reduce noise exposure



  • Vibration magnitude

  • Daily exposure time

  • Partial exposure

  • 8 hour exposure

Vibration Assessment

  • Manufacturer’s data

  • National Institute for Working Life


  • Measurements


Vibration Pick-up

  • Measures

    • Displacement

    • Velocity

    • Acceleration

  • Accelerometer normally used

    • Parameters inter-related


  • Electromechanical transducer

  • Piezoelectric

  • Piezioresistive


  • Piezoelectric

    • Two piezoelectric discs produce a voltage on their surfaces due to a mechanical strain on asymmetric crystals

    • Robust and sensitive


Frequency analyser

Level recorder




Axis of Vibration

Accelerator Mounting

  • Good frequency response

  • Not affected by surface temperature

  • Contact surface must be flat

  • Difficult to use on hand tools

Accelerator Mounting

  • Good frequency response

  • Contact surface must be flat and clean

Accelerator Mounting

  • Rapid mounting

  • Suitable for triaxial measurements

  • Light

  • No sharp edges

  • Mainly limited to measurement on power tool handles

Accelerator Mounting

  • Can be used in cases where a fixed coupling is inapplicable, e.g. on soft or resilient materials

  • Only suitable for fixed hand position and where the handle is always being held

Accelerator Mounting

  • The presence of the adaptor may change tool operation and the vibration magnitude

  • Additional fixing (e.g. adhesive) is required for transverse measurements

Accelerometer placement

Accelerometer placement

Accelerometer placement

Accelerometer placement

Single tool, 8 hour TWA

Multiple tools

HAVS Exposure limits

HSE Action Level Recommendation:

2.8 m/s2 A(8)

Physical Agents Directive:

Exposure Action Value (EAV):

2.5 m/s2 A(8)

Exposure Limit Value (ELV):

5.0 m/s2 A(8)

HAVS Exposure limits

HSE Action Level Recommendation:

2.8 m/s2 A(8)

  • Based on magnitude of vibration in the dominant axis

  • Basing it on total value increases value by a factor of 1.4 on average to:

    4 m/s2 A(8)

Exposure equivalents

Exposure equivalents

Whole Body Exposure limits

Root Mean Square (RMS) or A8 method

Vibration Dose Value Method (VDV)

Root Mean Square (RMS) or A8 method

Uses units of metres per second squared normalised to 8 hours [m/s2A(8)] or A(8)

Produces a cumulative exposure using an average acceleration adjusted to represent an 8 hour working day

Vibration Dose Value Method (VDV)

Ues metres per second to the power of 1.75 and is known as Vibration Dose Value or VDV

Sensitive to individual high acceleration events and produces a cumulative dose over a (working) day.

Whole Body Exposure limits

Root Mean Square (RMS) or A8 method

  • EAV 0.5 m/s2, ELV 1.15 m/s2

    Vibration Dose Value Method (VDV)

  • EAV 9.1 m/s1.75 , ELV 21 m/s1.75

  • Login