Element -6 Hazards and controls associated with electricity

Element -6

Hazards and controls associated with electricity

1.      Hazards associated with use of electricity in the workplace

2.      Control measures associated with working with electricity

The element focus on electricity safety

·         Electricity is the common form of power and its use to power machinery, and heat and light out homes is almost universal across the world.

·         Unfortunately, electricity can kill and injure people

·         We should note that any work on electrical equipment and system is not for the non- expert and should always be done by competence person

On completion of this element, you should be able to

1.      Identify the hazard associated with the use of electricity in the workplace

2.      Identify the control measures that need to be taken when working with electrical system or using electrical equipment

3.      Be familiar with the basic concepts of electricity

4.      Understand the potential effects of electricity on human body

5.      Be able to recognize common electrical hazards

6.      Be familiar with electrical protective device

7.      Be knowledgeable of safe work practices.

What is electricity?

A physical agency caused by the motion of electrons, protons, and other charged particles, establishing itself as an attraction, revulsion, magnetic, glowing and heating effects etc. or

Electricity is the flow of electrical power or charge, it is both a basic part of nature and one of our most commonly used form of energy.

Each year in UK there are: 30 workplace death, 30 domestic deaths

·         Electric shock

·         Electric burn

·         Electrical arcing

·         Fires

·         explosions

Definitions:

Electrical current: flow or movement of electron through a conductor or continuous movement of electrons preceding a given point measured in amperes.

Alternating current (AC): a current which periodically changes its direction or the electric current is constantly reversing its directions of flow at a given frequency

Direct Current (DC): A current is a continuous flow of electric current from positive to negative poles or the current flows in one direction between positive and negative terminals.

Amps: the unit of measurement of current flow or the current carrying capacity of conductors or equipment (Expressed in amperes)

Ammeter: An eclectic meter used to measure current Calibrated in amperes.

Amplifier: A device use to increase the strength of a signal.

Appliance: Utilization equipment, generally other than industrial, normally builds in standardized sizes or types, which is installed or connected as a unit to perform one or more functions.

Battery: A device for turning chemical energy into electrical energy.

Conductors: Metal wires and cables that allow that the flow of electrical current. OR A material that allows electricity to flow easily. Ex: copper, steel, aluminum, and water ETC.

Capacitor: a device consisting of two conducting surfaces separated by an insulator and having the ability of storing electric energy also called a condenser.

Charge: the number of electrons held on the capacitor plates, the act of forcing electrons onto the capacitor plates.

Circuit: A continuous path for the flow of electricity.

Circuit breaker: A device designed to open and close a circuit by o automatic means and to open the circuit automatically on a fixed over current without damage to itself when properly applied within its rating.

Disconnected: A device, or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply or equipment (or a part of an electrical system) that is not connected to any source of electrical energy.

Electrical Equipment: Anything used, proposed to be used or installed fro use to generate provide, transform, rectify, convert, conduct, distribute, control, store, measure or use electrical energy.

Energized: electrically connected to a source of voltage.

Frequency: measured in cycles per second is expressed in Hertz in uk 50 cycles per second.

Fuse: An over current protective device with a circuit opening fusible part that is heated and served by the passage of over current through it.

Generator: A machine designed for the production of electric power.

Guarded : Covered, shielded, fenced, enclosed, or otherwise protected by means of suitable covers, casing barriers, rails, screens, mats, or platforms to  remove the likelihood of approach or contact by persons or objects to  a point of danger.

High Voltage: A voltage is excess of 1000 v AC or 1500 v DC voltages below these values are low voltage.

Hydroelectric power: power produced by using the power of water to turn the shaft a generator.

Insulator: Contain few free electrons-usually non metallic such as plastic, wood, rubber, glass etc.

Isolated: Equipment (or part of an electrical system) which is disconnected and separated by a safe distance (the isolating gap) from all sources of electrical energy in such a way that the disconnection is secure i.e., it cannot be reenergized accidentally.

Live: Equipment that is at a voltage by being connected to a source of electricity, live parts that are insulated and exposed so that they can be touched either directly or indirectly by conducting object are hazardous if the voltage exceeds 50V ac or 120 v dc in dry conditions.

Live Work: Work on or near conductors that are accessible and live or charged live work included live testing. Such as using a test instrument to measure voltage on a live power distributions or control system.

Load: The amount of power used.

Motor: A machine which converts electrical power into mechanical power.

Ohms’s: The unit of measurement of resistance.

Ohmmeter: An instrument for measuring resistance in ohms.

Panel Board: A single panel or group of panel units designed for assembly in the form of a single panel, including, buries and automatic over current devices, and equipped with or without switches for the control of light heat. Or power circuits, designed to be placed in the cabinet or cutout box placed in or against wall, partition, or other support and accessible only from the front.

Resistance:  Opposition to movement of electrons. Makes it possible to generate heat, control current flow and supply correct voltage to devices.

Remote- control circuit:  Any electric circuit that controls any other circuit through and relay or an equivalent device.

Single –phase: A term characterizing a circuit energized by a single alternating voltage sources.

Two-phase:  A term characterizing a combination of two circuits energized by alternating voltage sources which differ in phase by quarter of a cycle 90 degree.

Three phase: A term characterizing a combination of three circuits energized by altering voltage sources which differ in phase by 1/3^rd of a cycle 120 degree.

Transformer: A static electrical device which by electromagnetic induction regenerates AC power one circuit into another. Transformers are also used to change voltage from one level to another.

Voltage: Unit of measurement of electromotive force.

Volts: This unit of measurement of electrical pressure or electrical pressure, the force which causes current to flow through a conductor.

Watt: The unit of electrical power.

Ohms-Law: The higher the electrical pressure (V) or the lowest the circuit resistance (R) The higher is the current that flows in the electrical current. I=V/R.

I= is measured in amps (A) which is the electron flow current.

V= is measured in volts (V) potential difference or pressure.

R= the resistance is measured in ohms (Ω).        I=V/R

Electrical Power: Electrical power (p) represented by the flow of electrical current in a circuit, to be determined.

Power: (P) Voltage (V)*Current (I) When

V= is measured in voltes (V)

I= is measured in ampears(A)

P= is given in watts (W)

Leading Causes of electrical accidents:

1.      Drilling and cutting through cables

2.      Using defective tools, cables and equipment

3.      Failure to maintain clearance distance of 10 feet.

4.      Failure to de- energizes circuits and follows lockout / tag out procedures.

5.      Unqualified employees working with electricity

6.      Improper installation / use of temporary electrical system and equipment

7.      By passing electrical protecting device

8.      Missing ground points on extension cords

9.      Insufficient wiring

10.  Unprotected electrical parts

11.  Wires with bad insulation

12.  Ungrounded electrical system and tools

13.  Overloaded circuits

14.  Damaged power tools and equipment.

15.  Using the wrong ppe and tools.

16.  Overhead power lines

17.  Hazards are made poorer in wet conditions

18.  Damaged extension cords.

19.  Unqualified workers doing electrical work.

Main hazards of Electricity

1.      Electric shock

2.      Arcing

3.      Fire

4.      Burns

5.      Explosions

v  Electric Shock: Electric shock occurs when the human body becomes part of the path through which current flows it may be 2 types.

·         Direct Contact: Coming into contact with a conductor that is supposed to be live.

·         Indirect contact: coming into contact with a conductor that is not live in normal condition but has become live due to a fault.

v  Arc: Electricity can jump on air gap causing shock effects to person not in contact with conductor.

v  Fire:  Flow of electricity generates heat. It large flow passes through unsuitable conductor heat can lead to fire.

v  Burns: Heat of arcing or excessive flow through body causes tissue and damage.

v  Explosion: Explosion occur when electricity provides a source of ignition for an exposure. Mixture in the atmosphere.

Severity of Electronic Shocks

1.      Current in ampere (amt of current).

2.      Length of contact time (Duration of flow through body)

3.      Path through the body

4.      The voltage (110/220 or more).

5.      Conductivity/ resistance of the body.

6.      Conductivity of environment

7.      Nature of contact.

Effects of electricity on Body

1.      More than 3 milliamps : Painful shock

2.      More than 10 milliamps: muscle reduction

3.      More than 30 milliamps: lung paralysis

4.      More than 50 milliamps: ventricular fibrillation usually fatal.

5.      100 milliamps to 4 amps: certain ventricular fibrillation fatal.

6.      Over 4amps – Heart paralysis severe burns.

First effects of electricity shock on body

1.      Damage to the nervous system

2.      Fibrillation (irregular heart beat)

3.      Tissue burns at entry and exit

4.      Damage to internal organs

5.      Muscular reduction

6.      Physical strain

7.      Stop  breathing (respiratory paralysis)

8.      Stopping the heart (cardiac arrest)

Secondary effects of electricity shock on body

1.      Falling from height

2.      Loss of information

3.      Throw off (sudden moment of the body)

4.      Unplanned movement of machinery

5.      Failure control measures and security system.

How electric shock occurs

1.      Current travels in close circuit through conductors (water metal and human body)

2.      Shock occurs when the body became a part of the circuit current enters at one point and leaves at another point

Shock occurs in 3 ways.

A.     Contact with both conductors

B.      Contact with one conductor and ground

C.      With a tool contact with hot metal part and grounded 1,2 and 3.

If a person received an electric shock

Safety Measures:

1.       Do not touch injured person until the current is switch off.

2.       If the current cannot be switch off stand on some dry insulating material and use a wooden plastic implement to remove the injured person from the electrical source.

3.       Manage first aid if qualified

4.       Call professional help.

Causes of Electrical Fire

1.      Insufficient circuit for the current

2.      overloaded circuit

3.      incorrect fuses

4.      damage wiring and insulation

5.      loose connections

6.      over heating of cables

7.      over heating due to thermal insulation

8.      over heating due to lack of ventilation

9.      Flammable materials to close to electrical equipment.

Electrical Hazard General Control

1.      Proper grounding

2.      Use fuses and circuit breakers

3.      Guard live parts

4.      Lockout/ tag out

5.      Proper use of flexible cord

6.      Ensure competent person on site

7.      Use proper approved electrical equipment

8.      Qualified person install electrical devices

9.      Employee training.

Electrical hazard common control methods

1.      Extension cord should only be used on temporary basis in situation where fixed wiring is not possible.

2.      Do not use extension cord as permanent wiring they may not be able to carry the load.

3.      However if it is necessary to use the extension cord never runs it across walkways. It causes a potential trapping hazard.

4.      Replace or repair electrical appliances that overheated, sparked, short out, smoked or have damaged cord.

5.      If wires are unprotected they may cause a shock to a worker comes into contact with them

6.      Cords should not be hang or nail, run over or wrapped around objects, tied or warped. This may break the wire or insulation

7.      Short circuit are usually caused by bare wires touching due to breakdown of insulations

8.      Cords in area of water or other conductive liquid must be approved for those location

9.      When the outer jacket of a cold is damaged the cord may be no longer be water resistance

10.  The insulation can absorb moisture, which may then result in short circuit or excessive current leakage to the ground. These codes should be replaced immediately.

11.  Electric cord should be examined on a routine basis or become worn and exposed wiring.

12.  If any defects are found the electric cord should be removed from service immediately.

13.  Pull the plug not the cord. Pulling the cord could break a wire causing a short circuit.

14.  Do not temper with fuses as this is potential fire hazard.

15.  Do not overload circuits they may cause the wires to heat and ignite insulation or other combustible.

16.  Keep office equipment properly cleaned and maintained.

17.  Ensure lamps are free from contact with flammable materials,

18.  Always use light bulb with the recommended wattage for your lamp and ceiling fixtures.

19.  Always follow the manufacturer recommendation when using or installing new office equipment.

20.  Wiring installation should always be made by a licensed electrician or other qualified person.

21.  All electronical appliances should have label of testing laboratory.

Portable Electrical Equipment

1.      Reduce voltage operations

2.      Use of residential current circuit breakers.

3.      Protected against overload

4.      Cable insulated

5.      Correct covering

6.      Sufficient socket outlets

7.      Correct maintenance and repair.

8.      Regular inspection and checks.

9.      Properly trained staff.

Electrical safety in office equipment

Safety Measures:

1.      Equipment of approved standard

2.      Maintenance of fixed installation

3.      Correct fuse

4.      Plugs correctly wired.

5.      No overloading of sockets

6.      Appliances switch off when not in use

7.      Cable correctly routed

8.      RCD used

9.      Connection wiring from defects

10.  System for reporting of defects.

Precaution for Working Electric live

1.      Permit to work

2.      Trained and competent staff

3.      Suitable information about the risk

4.      Suitable insulated tools

5.      Insulated barriers and displays

6.      Suitable instrument and test investigations

7.      Personal protective equipment/ rubber mat

8.      Restricted access

Control methods from electrical hazard

Fuses: A specially designed weak link which is designed to melt at schedule value of current

Circuit breaker: electromagnetic devices which perform the same function as fuse but operate fasten.

Earting: electricity will be always try to reach earth and earthing means providing a low resistance path to earth.

Isolation: Shutting off the electricity supply to an item of equipment and preventing system being mistakenly reconnected.

Reduce Voltage:  Reducing the main voltage by means of a transformer to a lower safer voltage e.g.: 110 volts or 55 volts.

Residual current Device: Compares the electricity flow to the equipment with the return flow and if a difference is detected the equipment is isolated.

Double Insulation:  Two separate layers of insulation are provide which allows for fault detection where one layer has failed the other still provides protection.