Occupational Health & Safety

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Physical & Electrical

Physical HazardsPhysical Hazards

• Noise• Radiation• Light• Vibration

These are

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Noise

NoiseWhat is it?

• Solids

• Liquids

• Gases

A travelling wave of pressureThese vibrations can travel through

Known as a medium

NoiseHow does it travel through?

• Solids

• Liquids

• Gases

Both longitudinal and transverse waves

Longitudinal waves

Sound cannot travel through vacuum

NoiseWhat is it characteristics?

• Amplitude

• Frequency

• Speed

Volume

Pitch

How fast it travels

For humans 12 Hz and 20 kHz

Upper limit generally decreases with age

SpeedThe speed of sound depends on the medium through which the waves are passing

• Air

• Fresh Water

• Steel

1,482 ms-1, 5 335 km/h, 3315 mph

5,960 ms-1, 21 460 km/h, 13 330 mph

343 ms-1,1 230 km/h, 767 mph20 °C air at the sea level

20 °C

The speed is dependant on the mediums:

• Density• Temperature Speed Density

Temperature

NoiseHow do we Measure it?

Sound Pressure in Pascals

Sound Pressure Level in decibelsLp or SPL

dB

dB = 2 x 10-5 Pa

p

But what about frequency

How Do We Hear

Pinna or AuricleGathers sound from the surrounding

environment and sends it down the ear canal.

Outer Ear

How Do We Hear

• Tympanic membrane (eardrum)• 3 small bones

• Malleus• Incus• Stapes

Middle Ear

carry sound to the inner ear

How Do We HearMade-up of two main parts:

Inner Ear

• Vestibular system• Cochlea

Responsible for balance

Made up of a system of complex hair cells (sensory cells) send impulses to the auditory nerve

FrequencyThe human ear does not hear

frequencies equally

The higher the frequency the less sensitive the ear is

Measurement equipment has to be filtered to adjust noise levels to match the human ear

Frequency

“A” Curve

“B” Curve

“C” Curve

“D” Curve

NoiseExcessive noise has various effects on people. Examples are:

• Tension Headache• Sleeplessness• Irritability• Nervousness• Increase In Blood Pressure• Increase In Stomach Acid Level• Inability To Concentrate

• These are generally considered short term.• Not considered permanent.

NoiseExcessive noise has various long term effects on people.

• What are they?

• What noise level is considered dangerous?

• How long must you be exposed before long term damage is done?

• What is the maximum peak noise level that any worker be exposed to?

Assignment Question

NoiseHow do we measure it?

If workers are stationary and noise is constant

Basic sound level meter

• Placed at the operator’s ear level

• Also record the length of time the person is exposed to that noise

What type of filtering must it have?


If workers are stationary and noise peaks

Basic sound level meter

• Gun fire• Jet engines• Nail guns

What type of filtering must it have?

Very loud noise

What is the maximum level?


If workers move around or the noise level varies

Personal Noise Exposure Meter

Records and calculates noise exposure with regard to:

• Frequency• Level• Length of time

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Radiation

Radiation

• Ionizing radiation• Non-ionizing radiation

Visible light is a form of radiation

Two basic types

RadiationIonizing radiation

Alpha Radiation

Beta Radiation

Gamma and X Radiation

A heavy, ejected helium nucleus

A light, ejected electron

Particle Radiation

Electromagnetic Radiation

•Ionizing radiation Ionizing radiation

RadiationIonizing radiation

Alpha Radiation

Beta Radiation

Gamma and X Radiation

• Not able to penetrate human skin• Harmful if the materials are inhaled, swallowed, or absorbed through

open wounds

Penetrate human skin to the "germinal layer,"

Penetrate several inches into human skin

Ionizing Radiation

Disruptive to biological systems, and can cause:

Mutations Cancer Cataracts Radiation sickness Radiation burns

Chronic Effects

Acute Effects

Ionizing Radiation

Parts of the body that are affected:

Blood-forming organsReproductive organsSkinBone and teethMuscleNervous system

Most Sensitive

Least sensitive

•Ionizing radiation Ionizing radiationNon-ionizing radiation

Non- Ionizing RadiationLow energy form of radiation

• Radio waves

• Micro waves

• Infrared light

• Visible light

• Ultraviolet light

Broken down into sections

• Burns to skin• Cataracts to the eyes• Skin cancer

Visible-light lasers damage the retina of the eyes

Cell damage due to heating effect

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Lighting

Clause 46 of the OHS Regulation 2001 states that employers must:

•Provide adequate lighting to allow workers to work safely, move safely, and enter and exit the workplace safely (including from emergency exits)

•Ensure that there is not excessive glare or reflection

•Ensure that lighting allows persons who are not workers to move safely within the place of work.

Lighting

Provide adequate lighting to allow workers to work safely, move safely

Lighting

Enter and exit the workplace safely (including from emergency exits)

AS/NZS 1680 series of standards provides lighting levels for specific industries

AS 2293 series of standards provides lighting levels for Emergency lighting

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Vibration

VibrationVibrations are mechanical oscillations,

produced by regular or irregular period movements of a member or

body about its rest position

Vibration can be a source problems at an engineering level, causing:

• Damage to equipment• Loss of control of equipment• Reduced efficiency of machines

The effect of vibration on people. Factors include: Point of application of the vibrationFrequency of the vibrationAcceleration of the vibrationDuration of the vibration

Vibration

VibrationThe body of a sitting person responds to vertical vibration as follows:

Musculoskeletal system (muscles, tendons and bones) can "be a path" for vibration and actually amplify the

vibration as it moves through the body

3- 4 Hz ....Strong resonance in the cervical vertebrae

4Hz.........Peak of resonance in the lumber vertebrae

5 Hz........High resonance in the shoulder girdle

20-30 Hz....High resonance between the head and shoulders

60-90 Hz....Resonance in the eyeballs

100-200 Hz..Resonance in the lower jaw

VibrationIs measured in three distinct patterns or ranges

• Low Frequency

• Middle Frequency

• High Frequency

Cumulative Damagezero to 2 Hz

2 to 15-20 Hz

greater than 20 Hz

Acute Damage

Vibration Vision Muscles Concentration Cardiac rhythm

Can affect:

Nausea Hyperventilation Raised blood pressure Increased energy dissipation leading to exhaustion

Can cause:

Vibration

Raynaud's Syndrome Hand-Arm Vibration Syndrome Carpal Tunnel Syndrome Tendonitis Various bone and joint disorders

Can cause long term disorders such as:

Reduction or Control

Source

Path

Receiver

Vibration

• Reduce vibration intensity/ avoid resonances • Regulate tool speed/ tool balancing • Careful tool selection

• Limit exposure time • Rotate personnel • Provide rest periods/ minimize weight and • Use balancers

• Reduce vibration transmission

• Use vibration isolators/ adapt posture • Reduce grip and push forces/ reduce contact area

Reduction or ControlAnti-vibration gloves has been the most prevalent

preventive measure taken by some industries

Vibration

Are only effective in the high frequency ranges

Most anti-vibration gloves actually amplify vibrations below 75 Hz while dampening the higher frequencies

Most handle wraps or foam have this same effect

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Electricity

In NSW there are 12 fatalities per year due to electrocution

What effect has electricity has on the human body

The factors that affect the severity of electric shock

Equipment designed to reduce the possibility of electric shock

Work methods around electrical equipment.

First aid after electric shock

How does the human body move?

Electricity sees you as a piece of meat

What affects the severity of electric

shock?

Time

Current

Path

The longer, the more damage

The greater the current, the greater the heat

Does the current go through major organs?

• Heart• Lungs

Time & Current Graph For Humans

Time in milliseconds Current passing through the body in mA

See AS/NZS 60479.1

Measured in:

Zone 1Usually No Reaction

Zone 2Usually no harmful

Physiological effects

Zone 3Usually no organic damage

Muscular Contractions

Difficulty breathing

Possibility of Cardiac Arrest

Zone 4Includes Zone 3

Zone 4 C1

Probability of Ventricular Fibrillation increased to 5%

Zone 4 C2

Probability of Ventricular Fibrillation increased to 50%

Zone 4 C3

Probability of Ventricular Fibrillation increased to above 50%

Protection Systems

Fuses & Circuit Breakers DO NOT directly protect against electrocution

What is the current required to cause burns in the human body?

What is the trip current of a Circuit breaker supplying power points?

Protection SystemsAS/NZS 3000:2007

1.5.3 Protection against electric shock1.5.3.1 ScopeProtection shall be provided against shock current arising from contact with parts that are live in normal service (direct contact) or parts that become live under fault conditions (indirect contact).

Fuses & Circuit breakers only protect against indirect contact

Protection Against Direct Contact

Protection Systems

Safety SwitchResidual Current Device (RCD)

No Fault

Working On Electrical Equipment

Must avoid working on live equipment

See Workcovers’ Code of practice “Low Voltage Electrical Work ” Publication No 0964

To make dead circuit must be isolated

Isolation Procedure Order

1. Assess the need2. Notify affected people/Seek authority3. Method of isolation4. Test for supply5. Isolate6. Danger Tag7. Test8. Test tester


1. Assess the needDo you have the skills, qualifications, knowledge of the equipment to safely isolate a piece of equipment?

Equipment is normally remote from the isolation point.

Two people are generally required


1. Assess the need2. Notify affected people/Seek

authorityAn isolation point may affect other machinery

May create a dangerous situation on other processes that are interlinked

Many companies require a “Clearance to Isolate” authorisation before isolation commences.


1. Assess the need2. Notify affected people/Seek authority3. Method of isolation

Can be many locations in the electrical installation

Main Switch

Circuit Protection

Isolation switch near device

Isolation point must be able to LOCKED OUT


1. Assess the need2. Notify affected people/Seek authority3. Method of isolation4. Test for supply

Test equipment must comply with Australian Standards

Tests that there is a supply to the device

Be aware of automatic controlled equipment


1. Assess the need2. Notify affected people/Seek authority3. Method of isolation4. Test for supply5. Isolate

Isolation point must be able to LOCKED OUT


1. Assess the need2. Notify affected people/Seek authority3. Method of isolation4. Test for supply5. Isolate6. Danger Tag

Two types of tag: Danger & Out of Service

Must be installed in such a way that it has to be removed to operate isolation point

Out of ServiceUsed to Protect Equipment Only

Can be removed by anybody with authorisation

Can stay on equipment until repaired or replaced

Personal DangerUsed to Protect Life

Can only be removed by the person who placed it there

Has to be removed when worker leaves danger area


1. Assess the need2. Notify affected people/Seek

authority3. Method of isolation4. Test for supply5. Isolate6. Danger Tag7. Test

Confirms that the correct isolation point has been used

Test equipment must comply with Australian Standards

Measure between:

Active & Neutral

Active & Earth + Exposed Conductive parts or Ground

Active & Other Actives

Isolation Procedure OrderIsolation Procedure Order

1. Assess the need2. Notify affected people/Seek authority3. Method of isolation4. Test for supply5. Isolate6. Danger Tag7. Test8. Test tester

Confirms that tester is functioning correctly

CautionWhy is the ‘attempt to operate’ isolation

procedure not an effective method of verifying that a circuit is de-energized?

mechanical failure of a switch contact cannot be determined by the‘attempt-to-operate’ method

THE END?

Occupational Health & Safety

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