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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

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Vibration
Vibration

Sean Mahar, PhD, CIH, CSP, PE


Vibration introduction
Vibration Introduction

  • Types

  • Problems

  • Controls

  • Measurements

  • Standards


Sean mahar
Sean Mahar

  • BS, Sacred Heart University

  • MS, Texas A&M University

  • PhD, University of Iowa

  • Certified Industrial Hygienist

  • Certified Safety Professional

  • Professional Engineer


Experience
Experience

  • U of Wolverhampton, 4 years

  • Ohio University, 3 years

  • Worksafe Iowa, 3 years

  • US Navy, 9 years

  • Tracor, 1 year


Educational objective
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
Definitions and measurements units

Units of measurement - understanding of acceleration amplitude

Velocity amplitude displacement amplitude


Definitions and measurements units1
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
Monitoring instruments

Vibration transducers

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

Meters

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


Making a survey
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 survey1
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
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
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 vibration1
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
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 limits1
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 limits2
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 limits3
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


Vibration1
Vibration

  • oscillatory motion of a system


Vibration2
Vibration

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



Vibration parameters
Vibration Parameters

  • Displacement

  • Frequency

  • Velocity

  • Acceleration


Displacement
Displacement

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)


Velocity
Velocity

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)


Acceleration
Acceleration

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)








Effects depend on
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).


Vibration4
Vibration

Segmental or Hand-Arm Vibration

General or Whole Body Vibration


Segmental or hand arm 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
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.



Symptoms
Symptoms

  • 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


Symptoms1
Symptoms

  • 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
Primary syndrome names only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Raynaud's syndrome

  • Traumatic Vasospastic Disease

  • Vibration White Finger

  • Hand Arm Vibration Syndrome


Characteristics
Characteristics only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • 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


www.whitefinger.co.uk only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Causes
Causes only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • 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


Factors
Factors only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Physical

  • Biodynamic

  • Individual


Physical factors
Physical Factors only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Dominant frequencies & vibration direction

  • Years of employment & daily duration

  • Temporal exposure pattern

  • Non-occupational exposure


Biodynamic factors
Biodynamic Factors only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Grip forces

  • Surface area & mass of hand

  • Handle orientation & texture


Individual factors
Individual Factors only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Susceptibility

  • Vasoconstrictive agents

    • (smoking, drugs)


Frequency dependence only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Taylor pelmear c lassificatio n
Taylor-Pelmear only upper limbs, legs can be affected if they come into contact with vibrating equipment. Classification


Taylor pelmear c lassificatio n1
Taylor-Pelmear only upper limbs, legs can be affected if they come into contact with vibrating equipment. Classification


Taylor pelmear c lassificatio n2
Taylor-Pelmear only upper limbs, legs can be affected if they come into contact with vibrating equipment. Classification


Taylor pelmear c lassificatio n3
Taylor-Pelmear only upper limbs, legs can be affected if they come into contact with vibrating equipment. Classification


Taylor pelmear c lassificatio n4
Taylor-Pelmear only upper limbs, legs can be affected if they come into contact with vibrating equipment. Classification


Stockholm scale for vascular symptoms
Stockholm scale only upper limbs, legs can be affected if they come into contact with vibrating equipment. for vascular symptoms


Stockholm scale for vascular symptoms1
Stockholm scale only upper limbs, legs can be affected if they come into contact with vibrating equipment. for vascular symptoms


Stockholm scale for sensorineural s tages
Stockholm scale only upper limbs, legs can be affected if they come into contact with vibrating equipment. for sensorineuralstages


Control
Control only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Control measures
Control Measures only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Anti-vibration tools

  • Anti-vibration gloves

  • Safe work practices

  • Warm clothing, including gloves

  • Avoid holding the tool too tightly


Control measures1
Control Measures only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Regular rest breaks

  • Rest the tool

  • Regular equipment maintenance

    • eg keeping cutting tools sharp

  • Reduce smoking


Whole body vibration
Whole Body Vibration only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Whole body vibration1
Whole Body Vibration only upper limbs, legs can be affected if they come into contact with vibrating equipment.

Vibration energy absorbed by body tissue and organs.


Whole body vibration2
Whole Body Vibration only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Spinal column disease

  • Digestive system problems

  • Cardiovascular effects

  • Motion sickness

  • Discomfort

  • Loss of balance and concentration

  • Fatigue


Whole body vibration3
Whole Body Vibration only upper limbs, legs can be affected if they come into contact with vibrating equipment.

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

  • Leads to

    voluntary/involuntary contraction causing fatigue esp. at resonant frequency


Whole body vibration4
Whole Body Vibration only upper limbs, legs can be affected if they come into contact with vibrating equipment.

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

  • some studies have even shown radiographic changes


Whole body vibration5
Whole Body Vibration only upper limbs, legs can be affected if they come into contact with vibrating equipment.

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


Resonance
Resonance only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • 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
Very low-frequency 0.1 - 1 Hz only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • 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
Low-frequency 1 - 80 Hz only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • 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 only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Control1
Control only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Control measures2
Control Measures only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • 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


Assessment
Assessment only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Assessment1
Assessment only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Vibration magnitude

  • Daily exposure time

  • Partial exposure

  • 8 hour exposure


Vibration assessment
Vibration Assessment only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Manufacturer’s data

  • National Institute for Working Life

    • http://umetech.niwl.se/Vibration/

  • Measurements


Measurement
Measurement only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Vibration pick up
Vibration Pick-up only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Measures

    • Displacement

    • Velocity

    • Acceleration

  • Accelerometer normally used

    • Parameters inter-related


Accelerometer
Accelerometer only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Electromechanical transducer

  • Piezoelectric

  • Piezioresistive


Accelerometer1
Accelerometer only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Piezoelectric

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

    • Robust and sensitive


Measurement1
Measurement only upper limbs, legs can be affected if they come into contact with vibrating equipment.

Frequency analyser

Level recorder

Pre-amplifier

Accelerometer


Measurement2
Measurement only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Axis of vibration
Axis of Vibration only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Accelerator mounting
Accelerator Mounting only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Good frequency response

  • Not affected by surface temperature

  • Contact surface must be flat

  • Difficult to use on hand tools


Accelerator mounting1
Accelerator Mounting only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Good frequency response

  • Contact surface must be flat and clean


Accelerator mounting2
Accelerator Mounting only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • Rapid mounting

  • Suitable for triaxial measurements

  • Light

  • No sharp edges

  • Mainly limited to measurement on power tool handles


Accelerator mounting3
Accelerator Mounting only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • 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 mounting4
Accelerator Mounting only upper limbs, legs can be affected if they come into contact with vibrating equipment.

  • 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 only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Accelerometer placement1
Accelerometer placement only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Accelerometer placement2
Accelerometer placement only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Accelerometer placement3
Accelerometer placement only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Single tool 8 hour twa
Single tool, 8 hour TWA only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Multiple tools
Multiple tools only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Havs exposure limits
HAVS Exposure limits only upper limbs, legs can be affected if they come into contact with vibrating equipment.

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 limits1
HAVS Exposure limits only upper limbs, legs can be affected if they come into contact with vibrating equipment.

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 only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Exposure equivalents1
Exposure equivalents only upper limbs, legs can be affected if they come into contact with vibrating equipment.


Whole body exposure limits
Whole Body Exposure limits only upper limbs, legs can be affected if they come into contact with vibrating equipment.

Root Mean Square (RMS) or A8 method

Vibration Dose Value Method (VDV)


Root mean square rms or a8 method
Root Mean Square (RMS) or A8 method only upper limbs, legs can be affected if they come into contact with vibrating equipment.

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
Vibration Dose Value Method (VDV) only upper limbs, legs can be affected if they come into contact with vibrating equipment.

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 limits1
Whole Body Exposure limits only upper limbs, legs can be affected if they come into contact with vibrating equipment.

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


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