LSEEE101A 9119A Physical & Electrical. Physical Hazards Noise Radiation Light Vibration These are.
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Transcript of LSEEE101A 9119A Physical & Electrical. Physical Hazards Noise Radiation Light Vibration These are.
LSEEE101A9119A
Physical & Electrical
Physical HazardsPhysical Hazards
• Noise• Radiation• Light• Vibration
These are
LSEEE101A9119A
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?
NoiseHow do we measure it?
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?
NoiseHow do we measure it?
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
Noise
LSEEE101A9119A
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
LSEEE101A9119A
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
LSEEE101A9119A
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
LSEEE101A9119A
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)
RCDs
No Fault
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
Isolation Procedure Order
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
Isolation Procedure Order
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.
Isolation Procedure Order
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
Isolation Procedure Order
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
Isolation Procedure Order
1. Assess the need2. Notify affected people/Seek authority3. Method of isolation4. Test for supply5. Isolate
Isolation point must be able to LOCKED OUT
Isolation Procedure Order
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
Isolation Procedure Order
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?