human vibration monitoring - larsondavis.com

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HUMAN VIBRATION MONITORINGINDUSTRIAL HYGIENE IN ACTION


Both whole body and hand-arm vibration can be a significant source of injury risk in the workplace. Effects of human vibration range from Hand-Arm Vibration Syndrome to lower back, neck, and shoulder issues. Vibration experienced in workplaces such as dental offices, mining operations, construction sites, industrial plants, and more should be taken seriously. When an employer suspects workers are being harmed by vibration, the best way to ensure safety is to measure the vibration to which the worker is exposed throughout a typical work day.

MEASURING WHOLE BODY AND HAND-ARM VIBRATION

There are no official national standards governing human vibration in the US, but there has been significant research in the EU and Australia, where standards have been in place since 2002 and 2001 respectively.

Tool and equipment manufacturers may publish vibration values, but in practice the vibration experienced by the user can vary widely depending on the condition of the tool, tool accessories (such as drill bits), the type of work surface, the worker’s posture or technique, or other factors. The best way to determine if a particular tool is safe for a given user in a given situation is to measure the vibration with a human vibration meter.

In fact, by providing simple to understand measurements correlating with published standards, a human vibration meter such as the Larson Davis HVM200 simplifies the process of protecting the workplace from vibration related injury. Simply wear the meter connected to a triaxial accelerometer mounted via an adapter at the location in which vibration is entering the body and go about typical work tasks. This guide to recommended weightings helps users understand how to set up the HVM200 meter for specific measurement scenarios. View results in the HVM200 App or G4 Utility Software, which display data in an easy-to-understand format, including values such as overall A(8) daily vibration exposure, vibration dose values, safe operating time limits, and exposure points.

The HVM200 app is available for download from both the Google Play® and The App Store®


HUMAN VIBRATION METRICS

EU Exposure Action Value (EAV) EU Exposure Limit Value (ELV)

m/s2 A(8) Exposure Points Vibration Dose Value (VDV)

(m/s^1.75)

m/s2 A(8) Exposure Points Vibration Dose Value (VDV)

(m/s^1.75)

Hand-Arm 2.5 100 N/A 5.0 400 N/A

Whole Body 0.5 100 9.1 1.15 529 21

Although there are no federal governmental regulations in the US for Human Vibration, the American Conference of Governmental Industrial Hygienists (ACGIH)®, a scientific non-profit whose stated purpose is the advancement of occupational and environmental health, has published Human Vibration standards called Threshold Limit Values (TLV)®. They are measured in the same units (m/s2 A(8)) as the EU standards.

ACGIH Action Level (AL) ACGIH Threshold Limit Values (TLV)

m/s2 A(8) m/s2 A(8)

Hand-Arm N/A 5.0

Whole Body 0.43 0.86

Other reported parameters from the HVM200 are A(8) Act. and A(8) Exp, reported in units of hours. These are the total calculated times an individual could use the equipment per day before reaching the user definable EAV and ELV, but can be customized to meet your needs. (The EAV and EVL are set by default to EU standards.)

an increased risk of damage to human health. Controls (either administrative controls or engineering controls – improvements to the tools, vibration-absorbing materials, vibration-damped equipment, etc.) to limit risk should be considered. ELV is the level at which the safe limits of vibration have been exceeded and risk of injury is severe. EAV and ELV are reported as an overall A(8) daily vibration exposure or with an exposure points system.

Note that another calculated parameter for whole body vibration reported by the meter is Vibration Dose Value (VDV). VDV is especially useful for cases in which the worker is exposed to impulsive whole body vibration such as shocks or jolts. VDV increases with measurement time, unlike the daily vibration exposure, which is an averaged value. Vibration Dose Value does not apply for hand-arm vibration.

Let’s take a look at some terminology. A(8), or daily vibration exposure, is the average vibration magnitude (calculated from the frequency weighted RMS acceleration measurements awx, awy, and awz and the measured exposure period Texp) over an 8 hour workday for a given piece of equipment in a given situation. Whether a worker wears the HVM over a few hours or all day, A(8) is calculated and reported. What’s considered an acceptable A(8) varies based on type of vibration (vibration in the whole body has different limits than vibration through the hand-arm) and location (various governmental agencies have different regulations).

Allowed exposure time (or the time the user can safely operate the tool or piece of equipment) is reported on the HVM using the EU standards of Exposure Action Value (EAV) and Exposure Limit Value (ELV). EAV is considered the vibration level at which there is

Because of the many factors that influence the effect of vibration on the human body, including differences in individuals’ susceptibility to vibration related injury, it is important to understand that none of the above values represent a distinct line between safe and unsafe practices. Instead, they should be thought of as a guide to assist in control of vibration hazards.


Having trouble developing a plan to assess human vibration? Consider these helpful guides as a starting point:

RESOURCES FOR ASSESSING HUMAN VIBRATION IN THE WORKPLACE

■ Health and Safety Executive (UK), Vibration at Work ■ EU Good Practice Guide for Whole Body Vibration ■ EU Good Practice Guide for Hand-Arm Vibration ■ Workplace Vibration Guidance Material from Safe

Work Australia ■ Workplace Exposure to Vibration in Europe: An

Expert Review ■ Vibration Measurement, Controls, and Standards Fact

Sheet from the Canadian Centre for Occupational Health and Safety

Other helpful Human Vibration Resources:

■ Safety and Health Magazine, Hand Arm Vibration Syndrome

■ NIOSH, Vibration Syndrome ■ Naval Safety Center, Acquisition Safety - Vibration

■ OSHA, On-Site Measurements, Vibration Monitors

From evaluating tools for purchase to implementing a whole-plant plan for monitoring and mitigating human vibration exposure, Larson Davis’ HVM200 Human Vibration Meter provides the needed data in a clear, easy-to-understand format. The HVM200 can help you provide a safer workplace for your employees.

How do we handle this when measuring human vibration? Researchers have come up with “weightings” to account for these differences. These frequency weightings, tied to various vibration conditions, are conveniently built in to vibration meters such as the Larson Davis HVM200.

Although there is strong consensus that whole body vibration can cause damage to the human body, the effects are complex and not yet completely understood. According to ISO Standards, we understand much more about the appropriate weightings to use for human comfort than for human health. The effects of vibration on health are best understood for a person in the seated position. The HVM200 has built-in settings for health in seated positions as well as user comfort in seated, standing, and recumbent positions.

UNDERSTANDING WEIGHTING FOR WHOLE BODY VIBRATION

Whole body vibration may be hazardous to your health - it can cause lower back pain, motion sickness, bone damage, and more. Measuring vibration is an important step in understanding these potentially adverse effects.

But what are the most important considerations in making whole body vibration measurements?

Different parts of the human body have different resonances. Certain vibration frequencies can be more damaging to some body parts than to others. For example, vibrations between 20 Hz and 30 Hz can cause resonance between the head and shoulders with vibration amplification of up to 350%!


When measuring human vibration, it is important to use the correct weightings for your measurement situation to account for the different resonances within the human body. To the right is a chart of common vibration scenarios with the appropriate frequency weighting factor for each axis. There are settings pre-programmed in the HVM200 for some vibration conditions. Note that in addition to the pre-programmed settings, a user can create and save custom settings as needed.

MEASUREMENTS WITH HVM200 HUMAN VIBRATION METER

Below is the ISO 2631-1 Definition for several weightings. For an exhaustive list of ISO Human Vibration Standards, see www.larsondavis.com/applications/hvm/wholebody vibration.

Vibration x-axis y-axis z-axis HVM200 Setting

Vibration transmitted through the seat, measured at the seat surface wd wd wk

ComfortSeat/HealthSeat

Vibration transmitted through the seat on a fixed-guide transport

system, such as a train or subway, measured at the seat surface

wd wd wdN/A

Vibration transmitted through the seat, measured at the seat back wc wd wd

Comfort-Back/Com-

fortMod

Vibration transmitted through the seat for a fixed-guide transport

system, such as a train or subway, measured at the seat back

wc wd wbN/A

Vibration transmitted at the feet for a person in a seated position wk wk wk

ComfortFeet

Vibration transmitted through the floor to a

standing personwd wd wk

N/A

Vibration transmitted through the floor under the pelvis to a person

in a prone positionwd wd wk

N/A

Vibration transmitted through the floor under the pelvis to a person

in a prone position when on a fixed-guide transport system, such

as a train or subway

wd wd wbN/A

Vibration transmitted through the floor at the head to a person in a

prone positionwj wd wk

N/A

Vibration transmitted through the floor at the head to a person in a prone position, when on a fixed-

guide transport system, such as a train or subway

wj wd wbN/A

Whole body vibration in buildings wm wm wmWmBuilding

All hand-arm vibration measure-ments wh wh wh

Hand-Arm

Rotational vibrations for a seated person we we we

ComfortRot

Frequency Weighting ISO 2631-1 Definition

wbz-axis vertical vibration, seated, standing, or recumbent

for fixed-guide transport systems

wcx-axis, horizontal, seat back, seated person

wdHorizontal whole body, x- or y-axis, seated, standing, or

recumbent; z-axis seated (at seat back)

weRotational, all directions, seated person

wfVertical whole-body, z-axis motion sickness (for low-fre-

quency whole body vibration signals), seated or standing

whHand-arm, all directions

wiVertical head vibration, x-axis, recumbent person

wjVertical whole body, z-axis seated (at seat surface),

standing, or recumbent

wkz-axis, vertical vibration for seated, standing,

or recumbent person

wmWhole body in buildings, all directions

This chart outlines the frequency weightings and HVM settings for various human vibration scenarios.

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human vibration monitoring - larsondavis.com

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