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Topic 5: Workplace Hazards - Coggle Diagram
Topic 5: Workplace Hazards
Noise
60dB : normal conversation level
85dB: avoid long-time exposure, no more than >8hrs
140dB not permitted
symptoms of noise-induced hearing loss
higher pitched sounds are hard to hear than lower-pitched sounds
feel like people are mumbling
harder to hear "sh", "s", "th", "f"
equivalent sound pressure level
the level of a constant sound which in a given time period, has the same hearing damage risk as a varying sound.
Noise control methods
(by hierarchy of controls)
Elimination
completely remove a very noisy process
Substitution
replace very noisy process with less noisy one
Engineering approach
Buy Quiet initiative
encourage companies to purchase quieter equipment to reduce worker noise exposure
Sound barriers
noise enclosure: reduction of 15db
noise panel: reduction of 10 db
noise curtain: reduction of 5 db
Reduce vibration
(a)
reduce driving force of vibrating surface
maintain dynamic balance, more balance force, less vibration
minimize rotational speed
(b)
reduce response of vibrating surface
add damping (water and foam)
increase stiffness
increase mass
(c)
reduce area of vibration surface
(d)
reduce velocity of water and the turbulence
Administrative approach
workers should be removed from workplace after spending max hours in place of 82 dB
arrange machine to not run at full capacity to reduce noise level
arrange high level noise machines operations are done when there are lesser workers
PPE approach
earmuffs (better protection and hygiene)
semi-insert ear plug
ear plugs (not comfortable, cannot be shared)
Ergonomics
10 principles of ergonomics
1. Keep everything within easy reach
keep frequently used items within easy reach
2. Work at proper heights
adjust your table, chair, workbench to proper height
3. Work in good posture
sit and stand upright, don't twist body or neck for extended time, avoid forward head position
4. Reduce excessive force
use muscle of legs when lifting heavy things
use tools when carrying heavy things
5. Minimise fatigue
rest when feeling tired, stretch your muscle and body to release static load
6. Reduce excessive motions
use tools to reduce manual labour
arrange workstation to minimise unnecessary movement to get tools **
7. Provide clearance and access**
regular housekeeping of desks to keep them uncluttered
8. Minimise contact stress
use a mouse wrist rest, dont rest wrists on edge of desk
9. Provide mobility and change of posture
at regular intervals, change postures, move and stretch
10. Maintain comfortable work environment
get good quality LED lamp, avoid too dark or too bright lighting
Proper way of sitting
keep eye level aiming at upper part of monitor
keep monitor at roughly arm's length away
sit in upright position and keep your head in line with torso
keep lower back supported by chair or cushion
minimise bend at wrists
Proper way of lifting heavy objects
get close to load. centre yourself over the load, stand with feet shoulder width apart
squat down and keep back in natural arch/ kneel down with one leg
hold load firmly with two hands, keep it close to body, use legs to lift up the load in one smooth motion
Injuries caused by improper lifting
lower back pain
80% of back injuries occur at L5S1 position
soft gel in middle of disc bursts through outer covering, presses on spinal nerves root causing pain.
Standing workers
anti-fatigue mat that provides cushion to feet
avoid standing for too long in one position to reduce build-up of stress and fatigue, stretch at regular intervals
adjust height of workbench to match height of worker to reduce bending of back when standing
wear proper and comfortable shoes, avoid wrong footwear such as high heels
Machinery hazards
4 common types of machinery hazards
1. Entanglement hazards
- loose items coming into direct contact with moving machine
require long hair to be tied, no jewelry etc.
2. Cutting hazards
machine or tools that have moving cutting elements
3. Crushing hazards
can be caused by rotating rollers , esp when using disposable gloves
4. Friction/Abrasion hazards
smooth parts of machine + high speed -> friction burns
fast moving conveyor belt, pulleys system
Machine guards
1. Fixed guards
physical barrier permanently attached to machine to prevent access to danger zone
2. Adjustable guards
moved or reconfigured to dimension of work at hand
3. Interlocking guards
shuts down power to machine whenever it is opened or pushed out of position
Safety devices
1. Safety mat
pressure sensor to detect weight
weight detected, switch closes, sends signal to stop machine
2. Safety camera
person enters warning zone, system can be set to sound alarm, slow down machine
person enters danger zone, system trigger emergency stop to shut down machine
3. Two-handed control device
both hands to activate machine, thus no hand will wander into the machine when in operation
4. Emergency stop
when pressed, immediately cut off power and stop operation of machine
to resume operation, emergency stop must be reset to normal position
Lock out-Tag out procedures
procedure to isolate electrical energy from equipment to prevent it from being accidentally turned on during maintenance
Announce shutdown
Shut down machine
Disconnect all energy sources
Apply lock-out and tag-out eg. padlock + durable tag
Verify isolation and lock-out
Electrical hazards
Consequences of electrical incidents
Electric shock (electric current moving)
Electrocution (fatal electric shock)
Electrical burns
Loss of muscle control (muscle spasms)
Heart & organ damages
Fire and/or explosion
Common sources of electrical hazards
Damaged electrical cords
Defective equipment (eg.low quality chargers)
Overloaded plugs or circuits
4.Wire laying on wet floor
Unsafe work practices
working with electrical equipment with wet hands/damp floors
always keep hands and surface dry
Using metal ladders to work on electrical equipment
place rubber mat under ladder to stop current flow
Never wear insulated electrical gloves
PPE for electrical safety
Insulating gloves
Rubber insulating gloves
Rubber insulating boots
Correct wiring of plug
Live wire (Brown)
high voltage
supply current from source to equipment
connected to fuse (melts upon overloading of current)
Neutral wire (blue)
zero voltage
carry current back to source from equipment
Earth/Ground wire (yellow/green)
zero voltage
connected to ground (safety feature in short circuit)
Common improper wiring practices
(i) improper use of cord gripper
has to be gripped on external insulator
(ii) reverse polarity
live and neutral wires connected in reverse
can result in shock hazard without melting the fuse
equipment can continue to run when switch is turned off
danger in light bulbs -> electric shock
(iii) failure to connect to ground
short circuit occurs -> electric current will go through technician -> electric shock
(iv) short circuit
An electrical short circuit occurs when there is an unintended low resistance connection between two points in an electrical circuit. This connection creates a path of least resistance for the electric current, causing it to bypass the normal load or intended pathway.
overload of current, damaging power source
electrical burns and electricution
ignition temperature reached, fire and explosion
caused by:
unintended low-resistance connection btwn 2 points in circuit
improper installation of ground wire
when live and neutral wires touch each other
Fire hazards
Fire triangle
Fuel
-paper, petrol, hydrogen etc.
Oxidiser
air, oxygen, oxidising agents eg. peroxides
Ignition source/heat
open flames, frictional sparks, electrical equipment, welding arcs
Flash points
definition
:
minimum temperature at which sufficient vapour is given of
to form a mixture with air which is capable of
sustained ignition when an ignition source is present
temperature < flash point : only sparkle will be observed, no ignition as there is not sufficient fuel to start fire
temperature => flash point : ignited, fire start and sustained
flammable liquids - can easily start ignition without direct contact with ignition source. must store below flash point
flammable limit
minimum and maximum concentrations in air of flammable gas/vapour at which ignition can occur
fall below lower flammable limit (LFL) : too diluted to ignite
above upper flammable limit (UFL): too rich to burn (insufficient oxygen)
fall withing LDL and UFL: capable of ignition
Classes of fire
Class A fires
: ordinary solid combustible materials (eg.wood, paper, fabrics, furniture, plastic, rubber)
Class B fires
: flammable liquids (eg. petrol, oils, kerosene, alcohol, paint thinners)
Class C fires
: flammable gases (eg. ammonia, hydrogen, propane, methane, liquefied petroleum gas LPG)
Class D fires
: combustible metals (eg. potassium, magnesium, sodium)
-
Class F fire
: cooking media (eg. vegetable oils and animal fats)
Fire extinguishers
Dry chemical/powder fire extinguisher
suitable for A,B,C and electrical fires
dry powder form physical barrier around burning materials, cut off supply of oxygen and prevent ignition of other materials
+ve
: versatile, fast extinguishing ability, protects user (forms screen btwn person and flame)
-ve
: residue is corrosive and sticky, difficult to clean. inhalation may cause health problems
Carbon dioxide fire extinguisher
B,C and electrical fires
reduce O2 content by dilution or displacement where is cannot sustain combustion
liquid CO2 removes heat from fire to below ignition point
+ve
: non-conductive, leaves no residue.
gas, can penetrate and spread to fire areas
easily stored under pressure for long period of time
-ve
: low cooling capacity, not suitable for big fire
must be applied very close to fire, short spraying range
CO2 not visible, leaks can result in asphyxiating environment
Foam fire extinguisher
AB fires
generate water-based foams to coat burning materials
similar to dry chemical
+ve
: effective against oil fires, float on top of oil
higher extinguishing power of water, as foam is water + air, higher volume when sprayed
-ve
: cannot be used on electrical equipment, contains water
contains flourine compounds, bad for health
Water fire extinguisher
A fires
when fires involve flammable solids
cooling, bring down temperature below ignition temperature
+ve
: cheapest, easiest to refill
high extinguishing capacity due to high latent heat of vaporization
-ve
: cannot be used for BC fires, cannot cover burning surfaces
conducive, cannot be used for electrical fires
cannot be used for combustible metals, explosion can occur as they react violently
Preventing fires
V
entilation - prevent vapour concentration to reach flammable range
I
gnition - remove all sources
C
ontainment - prevent accidental spills
E
xchange - eliminate/exchange flammable substance
S
eparation - storage area, etc.