Hazards Flashcards
Define a hazard
A potenial source of harm or adverse health effect on a person or persons
Define a risk
the likelihood that a person may be harmed or suffer adverse health effects if exposed to a hazard
What are the four specific hazards associated with installation of electrical systems?
- Electric shock (direct & indirect)
- Burns
- Fires
- Explosions
Define an electric shock
The physiological reaction, sensation or injury caused by electric current passing through the (human) body
What are the direct dangers of an electric shock?
Three things
- stoppage of breathing
- stoppage of regular heart rhythm
- burns
What are some examples of secondary events which could result in indirect danger from an electric shock?
- Falls
- Fires
- Explosions
Roughly what is the smallest amount of current that a human can percieve?
1 milliamp (1mA)
What amount of current can seize the human heart muscle?
80 milliamps (80 mA)
What is electrocution?
A fatal electric shock
What is a direct contact electric shock?
When a person recieves an electric shock as a result of touching live conductive parts
(Under non-fault conditions)
What is an indirect contact electric shock?
When someone recieves an electric shock from conductive parts which are not normally live.
(Under fault conditions)
What does the International Electrotechnical Commision (IEC) recommend to prevent direct contact electrical shocks?
Degrees of ingress protection (IP)
What makes electrical burns so dangerous?
They may not be visible on the skin, there may be a small mark where the current entered the body but there could be severe damage to internal tissues and organs.
What could happen if a short circuit occurs in an electrical installation?
It could result in a spark, which could ignite flammable material or gases, causing a fire or an explosion.
What defines an explosive atmosphere?
A mixture of gases, vapours, mist or dust in the air in which combustion spreads to the entire unburned mixture.
What does the term intrinsically safe mean?
That the electrical installation cannot ignite the potentially explosive atmosphere.
At least in the design/ installation stage, could be tampered with.
Define the term intrinsically safe
Intrinsically safe equipment and wiring shall not be capable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a flammable or combustible atmospheric mixture in its most easily ignitable concentration.
Basically, it has to be designed so that it physically cannot use enough energy to create a sufficient enough spark to cause a fire or explosion.
True or false:
The mark of a skilled and conscientous tradesperson is a tidy and organised work space, free from trip hazards
True.
Preventing fires or trips is an excellent way of working.
Fill in the blanks:
Many things can be a ___ hazard in the work place, such as:
* ___ discarded tools, equipment and materials
* Spilled ___ (such as ___ and lubricants)
* Trailing ____ and welding ____
* Uneven _____
- trip
- carelessly
- materials
- oils
- cables
- hoses
- terrain
Under what kind of conditions are the potential hazards of electricity at work at thier highest?
In harsh conditions
Name four examples of harsh conditions
- Damp/ wet surroundings
- Out of doors
- Cramped spaces with a lot of earthed metalwork
- Where items of equipment are at higher risk than others
Which three parts of extension cables are particularly liable to damage?
- The plugs/ sockets
- The electrical connections
- The cable itself
Under which regulations should new electrical systems be installed/ maintained?
BS7671: 2018 Requirements for Electrical Installations
True or false:
Electrical equipment used in potentially explosive atmospheres doesn’t require special attention/ advice.
False.
U want boom?
Boom bad.
True or false:
The equipment used must be suitable for its purpose and environment to reduce potential hazards.
True.
Considerations must be made for the type of equipment as well as its suitability for where it will be located.
True or false:
Electrical equipment must be provided and maintained in a safe manner for a competant person to use.
False.
It must be safe for anyone to use, regardless of expertise.
True or false:
Existing installations should be properly maintained.
True.
Obviously.
When using portable equipment, which plug sockets should be used?
The closest available, so it can be shut off quickly in the event of an emergency.
If the plug is not a “moulded-on” type, what must be checked?
Two things must be checked and ensured
- all the wires are properly connected
- that the wires are in the correct terminals in the plug top
When using machinery, what should be nearby and accessible?
A clearly identified switch to cut off power in an emergency
True or false:
Using adapters is completely fine whilst working on site
False.
Enough sockets should be provided, as using too many adapters is a fire hazard, overloading them is dangerous.
Which sections of damaged cable should be replaced?
The entire section of cable
Which part of cables should be firmly clamped down to prevent them from being pulled out?
The ends of flexible cables, particularly the CPC.
How should lengths of cable be connected together?
By using appropriate and proper connectors
Where should RCDs be used?
Outside of the Equipotential Zone
Complete the following sentence:
Risks can be reduced by using ___, ____, ____ or battery ____ tools.
- air
- hydraulic
- hand
- powered
What voltages can temporary lighting be run at to improve safety?
- 12 volts
- 25 volts
- 50 volts
- 110 volts
True or false:
Battery powered tools are the safest tools to use on site
True.
Less cables and wires trailing means less risk of a slip or trip
What does CTE stand for?
What voltage of tool does it help operate?
Bonus point if you can describe what it do
- Centre-Tapped-Earth
- 110V
It’s a safety feature of a lot of sites and mains power, in the site version it is referred to as a 55V-0–55V system, where the centre of the second winding is connected directly to the Earth.
What is the “usual” rated tripping current of an RCD?
Not more than 30mA
What is the best place for an RCD?
Where else could it be placed if this is unavailable?
- Main circuit board
- Plug top device
True or false:
Trip hazards are often easily prevented
True.
It is the responsibility of everyone to keep their working area tidy and free of any potential trip or slip hazards.
