Tool Box Talks: TBT 03: Electrical Safety at Work
PRESENTERS’ NOTES
ELECTRICAL SAFETY IN THE WORK-PLACE
AIMS: The aims of this presentation are to (1) raise the participants’ awareness of electrical safety by (2) encouraging participants to risk-assess their own workplaces by identifying possible electrical hazards, also (3) how to prevent deal with electrical hazards; (4) action in the event of an electrical accident / incident.
OBJECTIVES: at the end of this presentation the participants will (1) know and understand the main electrical hazards / risks in the work-place; (2) know and understand what can be done to reduce / prevent electrical hazards / risks; (3) know and understand key aspects of electrical emergency procedures and (5) know which type of fire extinguisher can be safely used on an electrical fire.
HAVE TO HAND HILLS’ POLICY ON ELECTRICAL INSTALLATIONS AND MAINTENANCE (INCLUDING PAT PROCEDURES) AND A COPY OF THE “LOCK OFF PROCEDURE
AND
AFTER EACH SLIDE / PAGE ASK FOR QUESTIONS / QUERIES / COMMENTS
IF APPROPRIATE, FEED THESE BACK TO H&S MANAGER
1 ELECTROCUTION: INJURIES:
1. The body is a conductor
2. The nervous system works by electricity
3. Electric shock = nerves overload :
• The heart stops pumping
• Muscles go into spasm
• The brain stops working properly
• ALSO: Internal and external burns
Find out what the participants know about the dangers of electricity – (electrocution, electrical burns, sparks / overheating causing fires). Explain how electrocution kills. Electric shock as little as 50v can cause:-
(1) muscles spasm = paralysis, this may prevent the casualty letting go of the conductor; or may make them fall (or jump) and cause injury
(2) heart spasm and fibrillation (quivering) as in a heart attack and therefore it cannot to pump blood = oxygen starvation to the brain;
(3) all nerves “fire” erratically – this disrupts the whole body;
(4) electrical resistance in the body and skin causes heating which “cooks” the tissues along the line that the current flows – the resulting deep burns can be very difficult to treat.
2 FIRE HAZARD DUE TO ELECTRICITY:
1. Current + electrical resistance = heat
Resistance from: damaged cable; coiled cable; overloaded circuit; loose connection
2. Spark / arc when current “jumps” an air gap in:
a. short circuits & switches;
b. “flash-over” & arc welding
3. HEAT + FUEL + AIR = FIRE
Use carbon dioxide or powder extinguisher
Before showing the page, find out if the participants understand how electricity can cause fires:
(1) sparks / arcing could be at 20,000degC (the surface of the sun is 5,000degC) – this is sufficient to ignite gases and other flammable substances; sparks / arcing from short circuits of electrical equipment and loose contacts; sparks from battery short circuits are enough to ignite flammable vapour;
(2) short circuited batteries overheat and may spark;
(3) overloaded circuits can overheat (e.g. motor burn-out);
(4) coiled extension cables can heat up by electrical induction.
(5) Static electricity discharge.
3 MAIN ELECTRICAL HAZARDS AT WORK:-
1. Damaged cables
2. Extension cables
3. Damaged equipment
4. Loose connections
5. Overhead power
6. Buried cables
7. Portable generators
8. Wet conditions
9. Static electricity
Find out what the participants consider to be the main electrical hazards in general and in their own work area (it may be that these need to be identified to the Health and Safety Manager):
(1) Damaged electrical cables insulation including outer insulator clamped into plug with no inner cable showing. Also conduits & trunking – easily damaged by plant / machinery / waste / tools / vandalism;
(2) Extension cables are easily damaged NOTE: to prevent electrical heating through electro-magnetic induction need to uncoil reels completely, including machinery with inbuilt cable reels
(3) Damaged electrical equipment, impact on cases or insulation – hitting / dropping;
(4) Loose connections (heating & sparking) – these may be in the supply circuit, the supply cable or inside the equipment itself.
(5) Overhead powerlines, 240v, 450v up to 400,000v mostly not insulated– get the participants to indentify problem: high vehicles + hoist / machinery crane jibs, 360 arms; may get “flash-over” even without direct contact especially in wet conditions CAUSE MANY DEATHS.
(6) Buried cables – can be damaged through digging / excavating / vehicles movement; need to consult ground-plans;
(7) Stationary / mobile generators – these generate “normal” currents – terminals may be exposed.
(8) Using tools in wet conditions e.g. outdoors particularly if they are damaged or their cable damaged; use 110v or battery powered in these conditions
(9) Static electricity – caused by moving insulators (e.g. conveyor belts) can spark when earthed
4 ELECTRICAL SAFETY – REDUCING RISKS (1):
THINGS TO REMEMBER (1):
1. 3-phase 450 volts; “mains” at 240v; Outside, use 110v
2. Use QUALIFIED ELECTRICIANS for electrical installations
3. NEVER interfere with an electrical circuit
4. NEVER interfere with electrical equipment
REPORT damaged electrical cable circuits / equipment
The next two pages look at some “do’s and don’ts” relating to electrical safety:
(1) With the participants, identify examples of the following types of electrical plant / equipment (a) 3-phase 450v for heavy static plant; (b) 240v for many smaller “indoor” equipment and tools; (c) 110v for use in possible wet conditions; (d) battery powered tools and equipment 12v-24v.
(2) Regulations demand that electrical wiring is done by NICEIC / qualified electricians who will certificate the work; they ensure the circuit is properly constructed with cable of the correct type that is laid in conduits or trunking and that the circuit is earthed and protected by circuit breakers. Emphasise that, unless qualified, they MUST NOT do electrical work.
(3) If circuits need to be altered, no one other than qualified electricians / permitted engineers are allowed to do this electrical work. Think of examples when this might be done e.g. adding electrical sockets to an existing circuit.
(4) If electrical plant / equipment develops a fault, no one other than qualified electricians / permitted engineers is allowed to open / work on electrical equipment to undertake servicing / repairs. Think of examples e.g. motors and pumps.
(5) Remind participants that they must report damaged to: insulation / plant / equipment / tools.
5 THINGS TO REMEMBER (2):
6. If you set up a generator ALWAYS get the circuit checked and certificated by a qualified electrician
7. Use Work Permit and Lock Off systems
8. If you get new electrical equipment do a Portable Appliance Test (PAT) at the earliest opportunity
9. If you obtain USED electrical equipment, do a PAT BEFORE use
(6) Remind participants that the current from electrical generator sets is just as dangerous as mains supply – so circuits / equipment must be checked by a qualified person. The outlet sockets must be in good condition.
(7) Make sure the participants understand the Hills Permit to Work and isolation / lock off system and who controls work permits.
(8) PAT for new equipment – explain the Hills policy and procedure for PAT on new electrical equipment (and the assets register requirement). Who do they need to contact to get equipment tested.
(9) PAT for used “second-hand” equipment / repaired equipment – explain the Hills’ policy and procedure with regard to PAT for this and who does this.
6 ELECTRIC SHOCK CASUALTY FIRST AID:
DO NOT TOUCH THE CASUALTY UNTIL YOU ARE CERTAIN THERE IS NO ELECTRICAL CURRENT RUNNING THROUGH THEIR BODY
1. Switch off the current / isolate the supply
2. Use a DRY NON-CONDUCTOR to separate the casualty from the electrically live object / cable
3. Check casualty’s vital signs – do CPR if needed
As in all emergency responses, emphasise the importance of NOT becoming another casualty. In the case of electrocution, the responder must ensure that the casualty is no longer in contact with the conductor that caused the injury. So:
(1) if possible, turn off / isolate the supply;
(2) if necessary, and if safe to do so, use a DRY INSULATOR to pull / push the casualty off the conductor and / or use it to pull / push the conductor away from the casualty;
(3) get suggestions from the participants as to what sorts of things they might find in their work place to do this. In work places close to high voltage (e.g. control rooms / plant rooms) it is usual to keep a special plastic “shepherds’-crook” for this job;
(4) get help – first-aider, emergency services;
(5) if the casualty is unconscious, check their pulse and breathing, if present put the casualty in the recovery position;
(6) if there is no pulse or breathing: if possible use an Automatic Defibrillator to re-set the heart. If required, IMMEDIATELY begin CPR. this is tiring so, every few minutes, swap with another person if possible;
(7) if burns are present, and if possible, get water to cool these;
(8) if the casualty has been unconscious they MUST be checked by a qualified medic, usually in hospital.
7 ELECTRICAL SAFETY HAZARD SIGNS:
1. All are black on yellow (SAME AS ALL WARNING SIGNS)
2. Most have a black triangle with a “lightning bolt”
3. Very many types
4. Most have hazard information
Emphasise that all electrical safety signs have a yellow background and have a black triangle with a “lightning bolt” or, the “Danger of Death” picture in black. There are numerous electrical safety signs – each one describes the nature of the hazard e.g. voltage level.
8 REVISION:
1. Electricity can cause INJURY / DEATH / FIRE
2. Common electrical hazards: damaged electrical cables; damaged insulation (clamp); damaged conduit/trunking; damaged electrical equipment / plant; no earth connection; overheating electrical equipment / cable; buried electrical cables; overhead electrical cables, sparks / arcs, static
3. Carbon dioxide or powder fire extinguishers
4. Recovery and first aid for electrocution
Go over the main points listed and ask the participants if they have questions or comments.
NOTE TO PRESENTER: YOU MUST FEED BACK FINDINGS / PROBLEMS IDENTIFIED / PARTICIPANTS’ PARTICULAR CONCERNS ETC ON ELECTRICAL HAZARDS / SAFETY TO H&S MANAGER
REFERENCES
The following give abundant background reading in the area of Electrical Safety at Work, all have hotlinks to further reading.
http://www.hse.gov.uk/electricity.htm
http://www.hse.gov.uk/lau/lacs/19-3.htm
http://www.legislation.gov.uk/uksi/1989/635/contents/made
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Reference / Version / Owner / Approved and checked HWS / Date of issueSee title bar / 001 / JJ / DMT / 11.09.2012