Electrical Protective Devices

There are various protective devices that can be used with portable electric power tools. These include the isolating transformer, the earth-leakage circuit breaker and the RCD.

 

Isolating Transformer

The isolating transformer plugs into the power supply and provides one of the safest ways to use a portable power tool. A portable power tool connected to an isolating transformer is fully isolated from earth. If a fault occurs, you will not receive an electric shock. You must plug the transformer into the power outlet (wall socket) so that it isolates the whole circuit. This is especially important when you’re using tools connected to extension cords. If you plug the transformer into the end of an extension cord, the cord is not protected.

 

Earth Leakage Circuit Breaker

An earth leakage circuit breaker also plugs into the power supply. It will cut off the power very quickly if a live part is touched or otherwise earths.

 

Residual Current Devices (RCD)

RCDs are devices that can sense a leakage of current in a circuit, and switch the circuit off. All RCDs legally require a test button to check whether they are operating efficiently and correctly. You should test an RCD regularly to ensure that it will work properly should a fault develop in the circuit. Types of RCD include

• The plugin RCD adaptor is suitable for use with most portable electric tools and appliances. You plug the tool, appliance or extension cord directly into the RCD adaptor
• The inline RCD extension cord is a safer alternative to a normal extension cord. You can plug it into any power outlet, and it protects the user of a power tool or appliance.
• The fixed wired wall mounted RCD is permanently wired into bathrooms, kitchens and laundries. You use this type of RCD to run shavers, hairdryers, smoothing irons and other similar appliances.
• The switchboard mounted RCD is permanently installed at the switchboard and can be wired to provide protection to a complete circuit.

 

Double Insulated Tools

The international symbol for double insulation is a square within a square. Double insulated tools have additional insulation between any exposed metal parts and the insulation of the current-carrying parts, hence the term “double insulation”. A double insulated tool may be used inside or outside, in wet or dry conditions or on earthed metals, but it is sensible to use an isolating transformer with double insulated tools. The lead supplying power to the tool needs to be electrically safe as well, either through an isolating transformer or RCD. Even when double insulted tools marked with a double square are used. Double insulation will not protect the user from risks caused by faulty leads or plugs.

 

Residual Current Devices (RCD) – How they work

From https://electricianrotorua.com/electrical-protective-devices/

Electrical Protective Devices syndicated from https://electricianrotorua.wordpress.com/

from
https://summerblakeley.blogspot.com/2019/10/electrical-protective-devices.html

What Are The Different Classes Of Fire?

Classes Of Fire

The fuel burning dictates the type of extinguisher you use to fight the fire. To help you understand this concept you need to know how fires are classified and which fire extinguishers are suitable for each class.

Class A Fires

Class A fires start when materials such as paper, rubbish, wood, or other carbon-based materials ignite.

Dry powder, foam and water extinguishers are suitable for this class of fire. Your best plan of attack would is to locate the nearest fire hose. This will give you a constant stream of water. The temperature at the base of the fire will cool to a point below that needed for combustion to take place.

Class B Fires

Class B fires involve flammable liquids such as paints, oil, and petrol. With these materials, its the vapours of fumes that burn rather than the liquid. Because the vapours a lighter than air, they can drift away from the seat of the fire, and then ignite, causing what’s called a flash-off.

This class of fire can be put out using carbon dioxide, dry powder ABE, or foam extinguishers. These starve the fire of the oxygen it requires for burning. Water will only help to spread the fire in this situation.

Class C FIres

C Class fires are fires involving flammable gases, e.g. natural gas, hydrogen, propane, butane.

Before fighting a Class C fire, you must turn off the gas if possible. ABE dry powder fire extinguishers are used to fight this class.

Class D Fires

D Class fires are fires involving combustible metals such as sodium, magnesium, lithium and potassium.

Specialised dry powders are available to control this class of fire. Sand also can smother the fire. Using water would produce hydrogen and cause an explosion.

Class E Fires

Class E fires are electrical fires. They usually start because of a short circuit or arcing in loose connections or because wiring becomes overheated. You must be very careful here because there is the added risk of electrical shock as well as the threat from the fire.

For all E Class fires, you should use either Carbon Dioxide extinguishers or Dry powder. Neither of these conducts electricity, and both starve the fire of oxygen. Never use water on Class E fires.

Class F Fires

These are fires involving cooking fats and oils. The high temperature of these types of fats and oil when on fire far exceeds that of other flammable liquids.

Wet Chemical extinguishers react with the surface of the oil or fat. This creates a soapy film barrier on the surface which seals off the air supply.

From

https://fireprotectiononline.co.nz/different-classes-of-fire/

From

https://fireprotectioninformation.wordpress.com/2019/10/04/what-are-the-different-classes-of-fire/

Fire Extinguisher Types

 

Fire Extinguisher Types

In New Zealand, fire extinguishers have a uniquely coloured band at the top of the cylinder for easy recognition. Because there are no universal extinguishing agents available, it’s essential to know the different fire extinguisher types. Some fire extinguisher types can make a fire worse or help spread it. Each fire extinguisher type needs to meet NZS4503:2005.

What Are The Classes Of Fire?

• Class A – fires involving carbon-based materials such as paper, wood or textiles.
• Class B – fires involving flammable liquids such as petrol, diesel or oils.
• Class C – fires involving flammable gases.
• Class D – fires involving combustible metals.
• Class E – fires involving electrically energised equipment.
• Class F – fires involving cooking oils and fats.

From

https://fireshop.co.nz/fire-extinguisher-types/

From

https://catherinelee4.blogspot.com/2019/10/fire-extinguisher-types.html 

NZ Fire Extinguisher Types And Fire Class

Fire is a constant danger when you’re using flammable materials in any workshop. Your safety depends on whether you can

• Identify the cause of the fire.
• Identify the correct extinguisher to use on different fires.
• Correctly operate the fire extinguisher.

Elements of fire

• Fuel, heat and oxygen must be present before there can be a fire:
• Fuel is anything combustible: any solid, liquid or gas that can burn, for example, wood, paper, oil, solvents and so on.
• Heat can come from flames, sparks, friction, electrical sources, hot pipes and equipment.
• Oxygen comes mainly from the air but also from some chemicals.

To put out a fire, remove one of the three elements by:

• Removing fuel to starve the fire.
• Removing oxygen to smother the fire.
• Cooling the heat by using water.

Types of fire

The fuel that is burning dictates the kind of extinguisher you use to fight the fire. To help you understand this concept, you need to know how fires are classified and which fire extinguishers are suitable for each class. We will look at the following classes of fire A, B, E, and D.

Class A Fires

Class A fires start when materials such as paper, rubbish, wood, cloth or other carbon-based materials ignite.

Class B Fires

Class B fires involve flammable liquids such as paints, oil and petrol. With these materials, its the vapours or fumes that burn rather than the liquid. Because the vapours are lighter than the air, they can drift away from the seat of the fire, and then ignite, causing what’s called a flash off. This instantaneously increases the size of the fire and is very dangerous.

Class D Fires

Class D fires are fires involving combustible metals such as sodium, magnesium, lithium and potassium. Specialised dry powders are available to control these fires.

Class E Fires

Class E fires are electrical fires. They usually start because of short circuit or arching in loose connections, or because wiring becomes overheated. You must be very careful here because there is the added risk of electrical shock as well as the threat from the fire. Switch off the power if you can safely.

Types Of Fire Extinguisher

Fire Extinguisher Types NZ

There are five types of fire extinguisher found throughout the working environment, they are

• Carbon Dioxide
• Dry Powder
• Foam
• Water
• Wet Chemical

The type of fire extinguisher you can use for each class of fire is as follows

Class A Fires: Water, dry powder, foam, co2 and wet chemical extinguishers are suitable for this kind of fire. Your best plan of attack is to locate the nearest fire hose. This will give you a constant stream of cold water. The temperature at the base of the fire will cool to a point below that needed for combustion to take place.

Class B Fires: these fires can be put out using foam, dry powder or co2 extinguishers. These starve the fire of the oxygen it requires for burning. Water is useless in these situations because it will only spread the fuel around and increase the base of the fire.

Class D Fires: these fires require specialised powders and are usually designed for a specific metal such as lithium, sodium, magnesium, etc. Sand can also be used to smother the fire. Using water would produce hydrogen (H2) and cause an explosion.

Class E Fires: use dry powder or co2 extinguishers to fight electrical fires. Neither of these conducts electricity, and both starve the fire of the oxygen it requires for burning.

You must never use water on an electrical fire. Water and electricity do not mix. Water is a good conductor and will suck the electricity to the source of the water.

Fire extinguishers are colour coded to help you identify the contents and which kind of fire they should be used on. They have easy to follow operating instructions. Make sure that you read these instructions before you have to use an extinguisher. This will save you time in a real emergency situation and help you feel more confident.

Fire Hose Reels

Fire hose reels should be located to provide a reasonably accessible and controlled supply of water to combat potential fire risks. The length of a fully extended fire hose is normally between 18 to 36 metres. Hose diameters are usually 13 or 19 millimetres ( internal measurement).

Fire hose reels usually deliver a minimum of 14 litres of water per minute. However, some hose reels have flows of up to 75 litres per minute. A control nozzle attached to the end of the hose enables the operator to control the direction and flow of the water.

from
https://fireprotectiononline.blogspot.com/2019/09/nz-fire-extinguisher-types-and-fire.html

Finding The Best Extinguisher For Your Needs

While it’s appealing to make a fast choice, it’s vital to guarantee you discover the perfect fit. After all, having the ideal fire extinguisher influences the security of your people and properties, and can even save lives. Here are simply some of the most important considerations to help you discover the best fire extinguisher:

 

LARGE VS SMALL

One of the most crucial elements when deciding on which fire extinguisher item is right for you is the size. On the opposite end of the spectrum, the bigger extinguishers, between 25 KG and 45 KG are much more pricey and require more training to use. However, they are essential in places where large and unsafe fires take place. So be sure to weigh up your needs before making a choice.

 

RECHARGEABLE VS DISPOSABLE

Another consideration for deciding on the best fire extinguisher for you is whether you need a non-reusable or refillable item. Refilling your fire extinguisher can just be done by a trained professional.

 

KIND OF EXTINGUISHER VS CLASS OF FIRE

Not all fire extinguishers are created equal. What’s inside the metal container can make a considerable effect on how you put out the flames. Here is a breakdown of the types of fire extinguishers you can purchase in New Zealand:

 

Water

Water fire extinguishers must primarily just be used on Class A fires, which are triggered by normal combustibles like rubber, wood, paper and fabrics. Remember, water can be harmful if applied to electrical fires, or fires triggered by cooking oils and fats. Which is why it is necessary to consider all risks present.

 

Foam

By producing a more cumbersome solution consisted of aqueous film-forming foam (AFFF), foam extinguishers are more reliable and sophisticated than water fire extinguishers. They are ideal for Class A fires caused by combustible products, as well as Class B fires, which are brought on by combustible and flammable liquids. However, they can be unsafe if used on Class E electrical fires.

 

Carbon Dioxide

Carbon dioxide CO2 extinguishers work by starving the fire of oxygen and eliminating the heat from the blaze. Generally for Class E electrical fires, which include electrical devices like heating systems, cooking area appliances and computers. These extinguishers have only restricted efficiency on Class A, Class B, and Class C fires fired up by flammable gases, so be sure to consider all possible hazards.

 

Dry Chemical Powder

Dry chemical ABE fire extinguishers work by discharging a powder that takes in the fuel from the fire source. They’re ideal for a variety of fires, including Class A, Class B, Class C and Class E, making them beneficial in various circumstances.

 

Wet Chemical

Wet chemical extinguishers work by cutting off the fire’s air supply and stopping the release of combustible vapours. They’re most suitable for snuffing out Class F fires, kitchen fires triggered by fats or oils.

from
https://fireprotectiononline1.wordpress.com/2019/09/27/finding-the-best-extinguisher-for-your-needs/

Fire Extinguisher Types NZ

Types Of Fire Extinguishers NZ 

New Zealand fire extinguisher types differ from those found around the world. It is essential that you are familiar which fire extinguisher is suitable for each class of fire. It’s simple to identify the type of fire extinguisher by the band of colour marked around the top of the cylinder.

The five main types of fire extinguishers found in NZ are:

1. Aqueous Film-Forming Foam
2. Carbon Dioxide
3. Dry Chemical Powder
4. Water
5. Wet Chemical

From

https://fireprotectiononline.co.nz/different-types-of-fire-extinguishers-new-zealand/

from
https://fireprotectiononline1.wordpress.com/2019/09/27/fire-extinguisher-types-nz/

Fire Triangle

Fire is a chemical reaction which needs three things to be present so it can happen: OXYGEN + HEAT + FUEL = FIRE
If one of these is not present, the fire cannot start. If one of these were taken from a fire, it would go out.

But how does this all work?

The parts of the fire triangle are these: Heat, Fuel and Oxygen.

These three parts are required for a fire to be present, so to secure against or put out a current fire we should eliminate a minimum of one of the aspects.

Various extinguisher types are created to get rid of several of those components to put out a fire.

As an example, water removes heat and foam can stop oxygen from getting in touch with fire by covering it similar to a blanket. To cut out the fuel source might be more difficult.

From

https://fireprotectiononline.co.nz/fire-triangle/

from
https://fireprotectiononline1.wordpress.com/2019/09/26/fire-triangle/