VIBRATION, VIBRATION ANALYSIS, VIBRATION CONTROL MEASURES, VIBRATION IN CONSTRUCTION, WORKPLACE VIBRATION LIMITS
Vibration
VIBRATION, VIBRATION
ANALYSIS, VIBRATION CONTROL MEASURES, VIBRATION IN CONSTRUCTION, WORKPLACE
VIBRATION LIMITS
Vibration is the result of the mechanical oscillation of an
object about an equilibrium point. The oscillations may be regular e.g. a
pendulum movement or random e.g. the movement of a machine, or a tire on a
gravel road. Any vibration has three measurable quantities that determine its
vibrational characteristics.
Amplitude
The movement of an object to a certain maximum distance on
either side of its stationary central position. Amplitude is the distance from
the stationary position to the extreme position on either side and is measured
in meters. The intensity of vibration depends on amplitude.
Frequency
A vibrating object moves back and forth from its normal
stationary position. A complete cycle of vibration occurs when the object moves
from one extreme position to the other extreme and back again. The number of
cycles that a vibrating object completes in one second is called frequency. The
unit of frequency is hertz (Hz). One hertz equals one cycle per second.
Acceleration
(Vibration Intensity)
The speed of a vibrating object varies from zero to a
maximum during each cycle of vibration. It moves fastest as it passes through
its natural stationary position to an extreme position. The vibrating object
slows down as it approaches the extreme, where it stops and then moves in the
opposite direction through the stationary position toward the other extreme.
Speed of vibration (acceleration) is expressed in meters per second (m/s) and
acceleration is expressed in meters per second squared (m/s2).
HEALTH EFFECTS OF VIBRATION
Vibration impacts the body part that is in contact with the
vibrating equipment. When a worker operates a hand-held power tool, such as a
chain saw, a grinder, or a jackhammer, vibration affects the hands and arms.
This type of exposure is called hand-arm vibration. On the other hand, when a
worker sits or stands on a vibrating floor or the seat of a moving vehicle or
crane, the vibration exposure affects almost the entire body and is called
whole-body vibration exposure.
The risk of vibration-induced injury depends on the average
daily exposure. Hand-arm vibration causes damage to hands and fingers and
especially to its blood vessels and nerves. The resulting condition is known as
white finger disease, Raynaud's phenomenon, or Hand-Arm Vibration Syndrome
(HAVS).
The symptoms are that affected fingers may turn white,
especially when exposed to cold, a loss of grip force, and sensitivity to
touch.
Vibration-induced white finger (VWF) is the most common
occupational health condition among operators of hand-held vibrating power
tools. The symptoms of VWF are aggravated when the hands are exposed to cold
temperatures.
Vibration can also cause changes in tendons, muscles, bones,
and joints, and can affect the nervous system. Collectively, these effects are
known as Hand-Arm Vibration Syndrome (HAVS). HAVS develop gradually and
increases in severity over time; hence it may take a few months to several
years for the symptoms to become clinically noticeable.
Workers affected commonly
report the following symptoms:
·
Attacks of whitening (blanching) of one or more
fingers when exposed to cold
·
Tingling and loss of sensation in the fingers
·
Loss of light touch
·
Pain and cold sensations between periodic white
finger attacks
·
Loss of grip strength
·
Bone cyst in fingers and wrists
·
Health Effects such as Lower back pain damage to
vertebrae and discs, ligaments loosened from shaking, Motion sickness, Bone
damage, varicose veins/heart conditions variation in blood pressure from
vibration.
Whole-body vibration can cause fatigue, insomnia, stomach
problems, headache, and "shakiness" shortly after or during exposure.
After daily exposure over some years, whole-body vibration can affect the
entire body and result in some health disorders. Sea, air, or land vehicles
cause motion sickness when the vibration exposure occurs in the 0.1 to 0.6 Hz
frequency range.
The combined effects of body posture, postural fatigue,
dietary habits, and whole-body vibration are the possible causes of these
disorders.
Hand Arm Vibration:
Jobs include: building maintenance; ground maintenance; gardening;
motor vehicle repair, tire changing; fabrication
Tools include chainsaws, concrete and road breakers, cut-off
saws, hand drills, jackhammers, radial drills, hammer drills; impact wrenches;
compaction machine, jigsaws, needle scalers, and powered lawnmowers, hedge
trimmers, strimmers, and power sanders.
Whole Body Vibration:
Jobs include gardening; civil works, transportation & warehousing.
Vehicles include: sit on lawn mowers; tractors, heavy road
vehicles; and heavy-duty forklift trucks, excavators and skid steer loaders,
and bulldozers
VIBRATION MEASUREMENT METHODOLOGY
The purpose of the Vibration Monitoring Methodology is to
enable managers to make a valid decision about the measures necessary to
prevent or adequately control the exposure of employees to HAV or
WBV. It also enables managers to demonstrate readily to others
who may have an interest, e.g. employees, safety representatives, and
enforcement authorities that they have from the earliest opportunity considered
the risks from vibration.
GENERAL STEPS:
·
Identify all existing powered tools, equipment,
machinery, and vehicles which potentially pose a risk of hand-arm vibration or
whole-body vibration.
·
Review and observe the conditions under which
such powered tools, equipment, and machinery are used to obtain a true and
representative appreciation of the nature of the work
·
Identify the maximum duration of their use ‘trigger
time’ for HAVS or work time for WBV on any working day, if necessary by keeping
a log or using monitoring devices
·
Assess the vibration magnitude from each piece
of equipment used. This information must be provided by the manufacturer,
however, manufacturers’ data will often come from testing under specific
controlled conditions which are very different from normal working practices
and therefore may significantly underestimate exposures in practice.
·
Additional information from on-site measurements
or databases of vibration levels shall be required.
CONTROL OF RISKS
VIBRATIONS
Using the Risk
Assessments
The information gathered during the qualitative and
quantitative risk assessments shall be used to achieve the following tasks:
·
Identifying medium or high-risk exposed to high
levels of vibration, and pinpointing work activities classified to be of high
and medium risk to vibration.
·
Establishing priorities and a timetable for
implementing the actions. This task shall be used to establish what long-term
changes are necessary, what benefits will be gained; and how many people will
be impacted by the changes.
·
Assigning roles and responsibilities for implementing
the action plan.
·
Monitoring, reviewing, and assessing the
effectiveness of the action plan.
Reducing Vibration
Reducing vibration risks in the workplace and minimizing
exposure shall be achieved using several methods, but as a rule, effective
vibration control is based on applying a combination of solutions described in
the Hierarchy of Controls.
The principal objective is to eliminate vibration at the
source, thus preventing exposure from occurring in the first place.
HEALTH SURVEILLANCE
Health surveillance is carried out by the Occupational
Health Service and is mandatory for employees who are regularly exposed to
vibration above the Exposure Action Value (EAV=2.5. m/s2)
Health surveillance is also offered to those exposed below
the EAV if they are at increased risk e.g. if they report a pre-existing
diagnosis of HAVS or any other condition of the hands, arms, wrists, or
shoulders, or any condition which affects circulation or nerve conduction such
as diabetes, carpal tunnel syndrome, etc.
Health surveillance
will involve:
Initial assessment before or very soon after first exposure.
This will usually be by questionnaire, with face-to-face follow-up where
required.
An annual assessment questionnaire sent out to certain
individuals by Occupational Health face-to-face review - This will be arranged
if the questionnaire reveals symptoms or if an individual reports symptoms
between health surveillance questionnaires, or every 3 years otherwise all
individual records are held confidentially as medical records. Where
appropriate, summary results for groups of employees will be reported back to a
manager to indicate the effectiveness of vibration control. Specific recommendations
may be made to a manager where an individual employee requires alteration to their
duties to protect against.
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