Hand-Arm and Body Vibration

Filename

Ensuring Good Human Vibrations

Colin Novak PhD, PEngAugust 06, 2015

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Human Vibration – Part of our daily lifeHuman Vibration:

Why care?

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For some it can be too much …

Vibration at workcan be a health risk: Long and frequent

exposure to excessive vibrations

Often combined with unfavourable climate conditions (cold and wet environments)

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Hand Arm Vibration (HAV)Repeated and frequent use of hand held or guided vibrating tools may cause Hand-arm vibration syndrome (HAVS) which causes symptoms in fingers, hands and arms. The most known is white fingers:

Symptoms of HAVS:• White finger symptoms• Nerve symtoms• Aches and pains

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Whole Body Vibration (WBV)

Long term exposure to whole body vibration cause changes in lower spinal and abdominal part of body

Symptoms: Fatigue Headache Slower reaction Nausea

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What would be the consequences?

For the affected worker: Reduced quality of life:

Pain, difficulties to move, touch and control

Social implications:Impairment > disability > social isolation/psychological problems

For everybody involved:(employer, employee, insurance companies, …)

High costs:Loss of experienced worker, medical care, rehabilitation …

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There is a need to PREVENT

EU Vibration Directive (2002/44/EC)

The purpose of the directive is to:• Set minimum standards for controlling the risk• Define daily exposure limit• Define daily action limit above which workers should not

be exposed• Place requirements on employers to ensure that risks are

eliminated or reduced to a minimum

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Directive 2002/44 EC Foreword:

– Directive 2002/44/EC of the European Parliament and of the Council on the exposure of workers to the risks arising from physical agents (vibration) seeks to introduce, at Community level, minimum protection requirements for workers when they are exposed, in the course of their work, to risks arising from vibration.

Directive 2002/44/EC:– Gives ‘exposure limit values’ and ‘exposure action values’,– Specifies employers' obligations with regard to determining and

assessing risks, – Sets out the measures to be taken to reduce or avoid exposure and

details how to provide information and training for workers. Any employer who intends to carry out work involving risks arising from exposure to vibration must implement a series of protection measures before and during the work.

– Requires the Member States of the EU to put in place a suitable system for monitoring the health of workers exposed to risks arising from vibration.

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Risk evaluation - methodology

1. Risk evaluation - general2. Assessing daily exposure by:

- Exposure duration- Vibration magnitude

- measurement, - manufacture data, - other sources

- Daily exposure calculation- A(8)- VDV

3. Reduction program:- Risk control

- substitution- equipment selection- purchasing policy- maintenance- training, etc

4. Monitoring and repeating risk assessment:

Risk evaluation

Start

End< 0,5ms-2

Risk controls

Reduction program

Daily exp. assessment

>0,5ms-2

>1,15ms-2

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Tools needed for risk assessment

Requirements come from standards:

Equipment for measuring and assessing vibration (ISO 8041: 2005) Human response to vibration – Measuring instrumentation

Making measurements:• Hand-arm (ISO 5349)• Whole-body (ISO 2631)

Risk evaluation (EU Vibration Directive 2002/44/EC)

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Equipment standard

ISO 8041:2005 (Human response to vibration – Measuring instrument)

It defines:• Measurement parameters (RMS, VTV, MTVV, VDV)• Technical specification (dynamic range, linearity, etc.)• Filters (weighting curves, tolerances)• Pattern evaluation• Calibration and verification• Tests for mounting methods

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What parameters are needed?

Vibration directive allows two vibrationassessment methods:

● Daily exposure, A(8) - the continuous equivalent acceleration, normalised to an 8 hour day

● Vibration dose value (VDV) is a cumulative dose (used in some countries for whole-body)

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Action and limit values set by Directive

Hand/Arm Whole Body

Daily exposure limit value A(8) 5 m/s2 1.15 m/s2

(or VDV = 21 m/s1,75)

Daily exposure action value A(8) 2.5 m/s2 0.5 m/s2

(or VDV = 9.1m/s1,75 )

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For more information

Good Practice guides:The evaluation and assessment of risks arising from exposure to vibration and the implementation of protection measures can be complicated. These non-binding “Guides to good practice" will facilitate the assessment of risks from exposure to hand-arm and whole body vibration, the identification of controls to eliminate or reduce exposure, and the introduction of systems to prevent the development and progression of injury.

MakingHuman Vibration Measurements

4447 Release Feb 2009

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Making vibration measurements

Measurements should be made to produce vibration values that are representative of the average vibration throughout the operator’s working period. It is therefore important that the operating conditions and measurement periods are selected to achieve this.

Measurements should be made over periods of at least 20 minutes. Where short measurements are necessary they should be at least three minutes long and should be repeated to give a total measurement time of more than 20 minutes (see EN 14253 for further advice). Longer measurements of 2 hours or more are preferable (half or full working day measurements are sometimes possible).

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What instrumentation to use? Human vibration analyzers shall comply with the EN

ISO 8041:2005 specifications It is important that accelerometers (vibration

transducers) are carefully selected. The vibration on hand-held and hand-guided machines

can be very high and can easily overload unsuitable transducers. Fixing transducers to the machine handles requires mounting systems that are rigid, lightweight and compact.

Human exposure to whole-body vibration shall be evaluated using the method defined in International Standard ISO 2631-1:1997.

Z

Y

X

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Standards require weighting of vibration signalStandards require weighting of vibration signal

Eye hole(ca. 25 Hz)

Head(in axis)(20 - 30 Hz)

Handle(50 - 200 Hz)Hand30 – 50Hz

Hand / armShoulder girdle(4 - 5 Hz)

Lungs

Lower arm

Spinal column(axial mode)(10 - 12 Hz)

Seated person

Abdominal mass (4 - 8 Hz)

Legs(Variable fromca. 2 Hz with knees flexing toOver 20Hz with rigidposture

Chest wall(50 - 60 Hz)

Body

Standing personArm(5 - 10 Hz)

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Weighting filters for health applicationsWeighting filters: Whole-body: Wd (x,y) and Wk (z) Hand-arm: Wh (all directions)

yh

zh

zh

xh

z

yx

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Hand-arm: Mounting systems and transducersHandle Adaptorwhere location at the handle/grip position is not possible

Hand Adaptorlocated at handle/grip position where direct mounting is not possible

Cube Adaptorlocated at handle/grip position where there is enough space

Triaxial accelerometer: 1.0 mV/ms-2

High-g accelerometer: 0.1 mV/ms-2

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Hand-arm: what is assessed?

222 _______ ZRMSTotalYRMSTotalXRMSTotalVTVRMS

Where:

RMS_VTV - Vibration total value

Total_RMS - Time-averaged weighted acceleration value over the measurement duration using linear averaging

X, Y and Z - Orthogonal axes of vibration direction

Daily vibration exposure:

Where:

Te - Effective exposure time of vibration in hours

Vibration Total Value of Total RMS

8_)8( eTVTVRMSA

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Hand-arm: Daily exposure limits

Exposure action value EAV: 2,5 m/s² Exposure limit value ELV: 5 m/s²

Source: Guide to good practice on hand-arm vibration

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Whole-body Vibrations: Transducer

Triaxial AccelerometerRubber disc(Seat pad)

Z

Y

X

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Whole-body: Mounting the Transducer

Z

Y

X

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Whole-body: RMS or VDV? The r.m.s vibration magnitude is expressed in terms of the frequency-

weighted acceleration at the seat of a seated person or the feet of a standing person, it is expressed in units of metres per second squared (m/s²). The r.m.s vibration magnitude represents the average acceleration over a measurement period. It is the highest of three orthogonal axes values (1.4TOTAL_RMS_X,1.4TOTAL_RMS_Y or TOTAL_RMS_Z) that is used for the exposure assessment.

The vibration dose value (or VDV) provides an alternative measure of vibration exposure. The VDV was developed as a measure that gives a better indication of the risks from vibrations that include shocks. The units for VDV are metres per second to the power 1.75 (m/s1.75), and unlike the r.m.s vibration magnitude, the measured VDV is cumulative value, i.e. it increases with measurement time. It is therefore important for any measurement of VDV to know the period over which the value was measured. It is the highest of three orthogonal axis values (1.4VDV_X, 1.4VDV_Y or VDV_Z) that is used for the exposure assessment.

Z

Y

X

Source: Guide to good pratice on Whole-Body Vibration

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Whole-body Daily vibration exposure - A (8)

Z

Y

X

0

exp4,1)8(TT

aA wyy

0

exp4,1)8(TT

aA wxx

0

exp)8(TT

aA wzz

Source: Guide to good practice on whole-body vibration

awx is ’Total RMS X’ on 4447

awy is ’Total RMS Y’ on 4447

awz is ’Total RMS Z’ on 4447

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Whole-body Vibration Dose Value - VDV

A cumulative dose, based on the fourth root of the fourth power of the acceleration signal. VDV has units of m/s1,75.

Z

Y

X

4/1exp

exp,

measzz T

TVDVVDV

4/1exp

exp, *4.1

measxx T

TVDVVDV

4/1exp

exp, *4.1

measyy T

TVDVVDV

Source: Guide to good practice on whole-body vibration

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Daily exposure limits for Whole-body

Exposure action value EAVA: 0,5 m/s² Exposure limit value ELVA: 1,15 m/s²

or

VDV action value EAVV: 9.1 m/s1.75

VDV limit value ELVV: 21 m/s1.75

Z

Y

X

Source: Guide to good practice on whole-body vibration

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Whole-body VTV

222222 _______ ZRMSTotalkYRMSTotalkXRMSTotalkVTVRMS zyx

Z

Y

X

Where:

RMS_VTV - Vibration total value

Total_ RMS - Time-averaged weighted acceleration value over the measurement duration using linear averaging

X, Y and Z - Vibration values in three orthogonal axes

kx, ky, kz, - Multipying constants 1,4 for x and y direction and 1 for z direction

Vibration Total Value of Total RMS

222222 _______ ZRMSVDVkYVDVTotalkXVDVTotalkVTVVDV zyx

Vibration Total Value of Total VDV

Where:

VDV_VTV - Combined vibration dose from three axes of translational vibration

Total_VDV - x, y and z vibration dose value over the measurement diration

kx, ky, kz, - Multipying constants 1,4 for x and y direction and 1 for z direction

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Type 4447 Measurement Solution

Cube adaptor

Charger

Handle Adaptor

Hand adaptor

USB Cable

4294 Calibrator

Seat pad3-axial accelerometer4520-002

DV-0459 Calibrator clipStrap for

mounting Seat pad

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Thank you for your attention

Any questions?