Transcript Electrical Safety

Electricity is the most commonly used item in our
daily use. When we are making extensive use of
electricity, a serious thought is also required to be
given to the dangers involved in its use.
Why Electrical Safety
 Out of 15 to 20 accidents in factories, one turn out to be
fatal
 More & more new areas are added everyday.
 Chances of accident is more as compared to other agency
due to extensive usage.
Know Electrical Primary Hazards
Electric shock
Electric fire &
explosion
Electric flash
Electric burns
Secondary Hazards
Person falling from height
Dropping of tools & objects
Health hazards due to release of
toxic gas & production of UV
rays
Psychological effects

Emotionally anxious

Distracted

More prone to accidents
Electrical Shock
 It is sudden & accidental stimulation of the body’s
nervous system by electric current. It is the result
of passage of electric current through the human
body
It occurs : When a person comes in contact with :
• Both wires of electric supply.
• One wire of an energized circuit & ground.
• Accidentally energized metallic part while standing on ground.
Severity of Electrical Shock
1.
2.
3.
4.
5.
6.
7.
Amount of current flow.
Path of current flow.
Period of current flow
Nature of current
Frequency
Resistance offered by body to
flow of current.
Duration of flow
Effect of Current in Human Body
Current
Effect on Body
1 to 8 mA
not painful
8 to 15 mA
painful shock
15 to 20 mA
painful shock, muscular control
lost
20 to 50 mA
breathing difficulties
50 to 100 mA
leads to death
200 mA &
more
severe burns, clamp down of
heart, leads to death.
Body Resistance
Body area
Resistance
(ohms)
Dry skin
1,00,000 to
6,00,000
Wet skin
1000
Internal body
Hand foot
400 to 600
Effect of Body Resistance
Person
in touch
with
live wire
P
POWER
SOURCE
N
•I
•I
=
V/R
=
230 / 100000 A
=
0.0023 A
=
2.3 mA
=
230 / 5000
=
0.046 A
=
46 mA
(Dry Condition)
(Wet Condition)
How Shock Occurs
1. By simultaneously touching the phase and
neutral conductor thus completing the circuit
through his body
Y
ALERNATOR
B
LOAD HAVING
METALLIC BODY
R
N
2. By touching the phase conductor and standing
on the ground
Y
ALTERNATOR
B
ELEC. EQPT.HAVING
METALLIC BODY
R
N
3. By touching a metallic part that has become live
by itself being in contact with an energised wire
Y
ALTERNATOR
B
ELEC. EQPT.HAVING
METALLIC BODY
R
N
Causes of Electrical Shock
1.
2.
3.
4.
5.
6.
7.
Insulation failure
Equipment failure
Poor maintenance
Wrong working method
Sub standard material
Unauthorized personnel
Lack of training and
knowledge
Shock Protection Methods
Isolation
Current limitation
Low voltage
Double insulation
Earthing
Isolation
 All
electrical equipment
should be isolated from
accidental
contact
&
approach
by
unauthorised men by
Providing barrier
 Panel boards, generators,
large motors, batteries
should be enclosed
 Low & medium voltage
OH lines should be kept
@20’ above the ground
Isolation Switches
 The switches should be connected in phase only
 The switches should be easy and free to operate
 Body of the metallic switches should be earthed
 Every DB should be provided with a switch
 It is advisable to keep switch as near as possible to the
work-place
POWER
SOURCE
P
N
Double Insulation
 Another insulation added.
 Double insulated power tools have nonmetallic body.
 Need not be earthed (two point plug is
sufficient)
Insulation
Functional
Protective
Electric Flash
 It is the result of the breaking of
circuit of electric current
 Higher the current, slower the rate
of separation of parts, the greater is
the flash
 Being a known hazard sufficient
preventive measures are taken to
guard against it like magnetic blow
out coil
 Electric flash generally affect the
eyes, if a person sees it with his
naked eyes. Personal protective
equipment has to be used
Electrical Fires and Explosions
Caused by :
1. Overloading
2. Incorrect fuses /protective
devices
3. Poor maintenance
4. Explosive atmosphere
5. Static electricity
6. Damage due to rodents,
termites and pests.
7.
Lightning.
8.
Water seepage.
Maintenance negligence
Temporary electrical connection
Bad switch contacts
Improper substitution of electrical
equipment and materials
Allowing equipment for regular usage after
repairs without complete check-up
Non-protection against mechanical
damages.
Failure of insulation level
Insulation failure occur due to following reasons:i) Reduction in voltage with standing capacity
because of excess temperature.
ii) Deterioration in mechanical properties due to
excess temperature where the insulation is
mechanically vulnerable and the mechanical
failure leading to electrical failure of the
insulation.
iii) Aging causes deterioration of the insulation.
iv) Sub-standard material are more prone to
insulation failure.
Electrical Burn
 When a person comes in contact with
live wire , due to heating effect of
electricity, receives electric burn.
 Electrical burns is another common
hazard associated with the use of
electricity.
 A flash over burn could be a serious
hazard dealing with very high voltages.
Type of Burns
1. Contact burn
2. Flash / arc burn
3. Scattering of vaporized metal
4. Arc eye & metal fume fever
Chemical Site
Electrical
Safety
requirements
Check in General for
 Neutral earthing
 Protective shed
 Body earthing
 Earth pit for body earthing
 Earth resistance
 Fuses
 Loose connection of cable
 Housekeeping
 Availability of Fire
extinguisher and type
PLUG TOPS
• PLUG TOPS SHOULD BE USED TO AVOID SHOCK
DANGERS.
• THREE POINT PLUG IN CASE OF METALLIC BODY
HAND TOOLS AND TWO POINT PLUG IN CASE OF
DOUBLE INSULATED HAND TOOLS.
METALLIC BODY
HAND TOOL
Fuses
Fuses are proven safety devices for overload
conditions
Check the fuses for their current ratings
Never replace fuse wire with ordinary copper
or aluminium wire
High rupturable cartridge fuses are now a
days easily available and has advantages
over traditional fuses
Earth Leakage Circuit Breaker


For portable power tools power supply is taken through ELCB
Saves persons from electric shock
POWER
SUPPLY

ELCB
SWITCH
BOX
Person in
touch
with
faulty
eqpt.
Having
elec.
Charges
on it”s
body
It opens the circuit when it senses leakage current from
earth.
Earth Leakage Circuit Breaker

For portable
power tools
power supply
should be
taken through
ELCB

ELCB

ELCB’s OF 30
mA
sensitivity ,
63Amps,

3 poles
63 A
Test the ELCB weekly and record it.
Cable Routing & Colours
 All electrical cables should be run either
overhead or underground
 Cable routing layout map to be prepared so
that it does not cause tripping hazards
 Welding and power cables not to be
 Single phase supply
overlapped
Phase - red
Neutral - black
Earth - green

Three phase supply


Phases
 Red
 Yellow
 Blue
Neutral - black
Cable Protection
•Protection against mech.
Damages
•Protection against heat
•Cables should be laid
away from welding cables
Cable Joints
 Staggered joints
CABLE 1
3/4”
3/4”
3/4”
3/4”
CABLE 2
 Joints are not to be overlapped
 One primary insulation and an overall
secondary insulation is to be done
 Proper insulation tape are to be used
Hand Lamps
Only 24V hand lamps are
to be used
Hand lamps are to be
enclosed
by
glass
surrounded by metal wire
mesh
Hand lamps used for
confined
space
work
should be of insulated
type with no joints
Hazard Control Measures
 Use of National standards.
 Observance of Rules & Regulations.
 Testing and inspection procedures.
 Making and warnings.
 Use of PPE’s
 Electrical work procedures
 Work Permit System
 Training and education
 Resuscitation techniques
 First aid of Fire Fighting.
Earthing
Earthing means:
“ Direct connections of all non
current carrying parts of electrical
equipments
such
as
metallic
framework, motor body, cable
armoured, earth terminal of socket
outlet, transformer to a earth plate.”
*The earth plate which buried in
ground should have a good electrical
connection to the surrounding earth.
Purpose of Earthing
1.
2.
3.
To avoid electric shock to human body.
To avoid risk of fire due to leakage current through
unwanted path.
To ensure that no current carrying conductor rises to a
potential w.r.t. earth than its designed insulation.
Requirement
 Earth connection should provide low resistance path.
 Setting & selection of protective devices should be such
that it should operate fast to cut of the supply.
Principle of Earthing
 National regulations on electricity require that all non-
current carrying metallic parts of electrical equipment
should be solidly connected to general mass of earth with
at least two earth connections.
 Principle behind Earthing that any leakage current which
accidentally energizes non-current carrying metallic parts
should flow back through the general mass of earth to the
substation so the protective devices are actuated to cut off
the supply as quickly as possible.
Types of earthing
1.
Wire or strip earthing
2.
Rod earthing
3.
Pipe earthing
4.
Plate earthing
Earth Resistance Value
 An healthy earth pit should have





the value as low as possible i.e 0.5
to 1 ohm.
Allowable earth resistance values
for different locations:
4 ohm = Electrical system &
metallic structures
7 ohm = Storage tanks
1 ohm = Main earth grid & pipe
lines
Earth Pit Resistance in Rallis Units
should be <1 ohm
Static Electricity
“ When two electrically neutral but similar surfaces come
in contact, they transfer electrons from one surface to
another, both becomes electrically charged so that one
surface lose charge and other gain charge. One will
become +vely charged & other –vely charged and a spark
discharge will occur if strength increases.”
Effects of Static Charge
 Fire & Explosion
 Discomfort & possible injury.
Source of Generation
1.
Liquids, gases flow in pipes, ducts, tanks, tanker, vessels.
2.
Liquids & gases under pressure from nozzles.
3.
Dragging a metal container along a insulated floor.
4. Movement of driving or conveyer belts.
5.
Pneumatic conveying of plastic pellets & blending.
6. Crystallization in an enamel coated vessel using solvents
with low conductivity.
Electrostatic Ignition
For static ignition, following conditions must present:
1.
Electrostatic charge generation must occur.
2.
Means for static charges to accumulate.
3.
The electrical field resulting from static charge must
be strong enough to provide a spark of sufficient
energy to cause ignition.
4. An ignitable mixture of vapor-air or dust-air be
present.
Protection from Static Charge
Bonding and earthing of
Equipment/ pipeline
2. Low velocity of fluid
3. Use of Antistatic material
4. Wearing of Antistatic
shoes
5. Use of static discharge
plate at Plant entrance
6. Earth Monitor to ensure
proper earthing of Static
charge in Tankers.
1.
Electrical Safety-Remember
Display electrical equipment & cable routing
layout
All electrical installation to be tested &
commissioned as per BIS codes
All DB’s should be covered
Earthing of all electrical installations
Regular maintenance
Follow rules and regulations
Follow safety measures
Adopt protective system
Insulation
Regular inspection
Any Question?
Safety Rules/ Standard
 IS 5571:1979 > Guide for selection of electrical equipment for
hazardous area (1st revision)
 IS 5572(Part 1):1944 > Classification of hazardous area for
electrical installation.
 ELECTRICAL INSTALLATIONS (CHEMICAL INDUSTRIES
SCHEDULE XI PART II OF THE PFR ,1952(Safety against
dust, corrosion, flammability & explosibility)
 DANGEROUS OPERATIONS (SECTION-87)
> Exposes any person to a serious risk of bodily injury,
poisoning or disease.
Contd…
Safety rules contd…

High Noise: Noise induced hearing loss (notifiable
disease no.22)
 MANUFACTURE
&
REPAIR
OF
ELECTRICAL
ACCUMULATORS ( SCHEDULE-III) > Hazardous process.
 EXPLOSIVE OR INFLAMMABLE , DUST,GAS ETC.
(SECTION-37) > Process that produces, dust, gas, fumes or
vapors that’s likely to explode on ignition: All safety
measure shall be taken to prevent any such explosion by
effective enclosures of all possible sources of ignition.
Electrical Safety General Rules
The Factories Act,1948 LIGHTING ( SECTION 17 )> In
every part of factory, provide & maintain sufficient & suitable lightingNatural or Artificial.
 PRECAUTIONS REGARDING THE USE OF PORTABLE
ELECTRIC LIGHT ( SECTION-36A)
> No portable light or portable tool of voltage exceeding 24V shall be
permitted for use inside a confined space.
>If flammables is likely to be present than no lamp or light other than flameproof construction shall be permitted.
Thank you
By Shailesh Mistry