construction of fire extinguisher

The Construction and Operation of Modern Fire Extinguishers

Modern portable fire extinguishers are typically Stored Pressure or Cartidge Operated Fire Extinguishers. Manufacturers of fire extinguishers tend to produce both types of fire extinguisher with stored pressure fire extinguishers being the most common.Fire Extinguisher Construction Materials.

Typically modern fire extinguisher bodies are constructed from Steel, Aluminium or Aluminium Alloy. These materials give the fire extinguisher a durable exterior to withstand knocks, external temperatures and corrosion. The cartridge in gas catridge operated fire extinguishers is usually coated in plastic to give the catridge extra protection against the contents of the fire extinguisher. There are two types are gas cartridges in modern fire extinguishers, these are; piercing disc and frangible pip cartridges. The piercing disc gas cartridge features a diaphragm which is pierced by a suitable shaped spindle. The frangible pip gas cartridge features a pip which is broken by a blunt spindle. In a gas cartridge operated fire extinguisher only the cartridge itself is pressurised whereas in a stored pressure fire extinguisher the entire body of the fire extinguisher is pressurised

How the different fire extinguishers work.

Stored pressure fire extinguishers work in the following way:-

 1. The fire extinguisher is operated by releasing the pin, breaking the tamper seal and pressing down on the fire extinguisher handle.

 2. The pressure stored within the top of the fire extinguisher (dry air or nitrogen) is released.

 3. The pressure forces down on the extinguishing agent within the fire extinguisher (water, foam, powder etc.)

 4.The extinguishing agent is forced up the syphon tube within the fire extinguisher, through the head cap and hose onto the fire.

 5.Some fire extinguisher hoses are fitted with a squeeze grip control to regulate the flow of the extinguishant. 

 

 Gas cartridge fire extinguishers work in the following way:-

 1. The fire extinguisher is operated by releasing the pin, breaking the tamper seal and pressing down on the fire extinguisher handle.

 2. The action of pressing down on the fire extinguisher handle pushes a pin down onto the seal of the gas cartridge.

 3.The pin pierces the seal on the gas cartridge and releases the pressure in the gas cartridge.

 4.The pressure within the fire extinguisher from the gas cartridge then forces down on the extinguishant.

 5.The extinguishant is then forced up the syphon tube, through the head cap and hose onto the fire

Fire and safety

To achieve maximum effect, the quantity of heat energy absorbed should be as great as possible. The properties of a good cooling agent are therefore:

• High specific heat capacity (thermal capacity)
• High latent heat of vaporisation
• High heat of decomposition

Water is a good cooling agent because of its high thermal capacity and latent heat of vaporisation. This, combined with the fact it is available in large quantities, makes it by far the most widely useful fire extinguishing agent.

The role of decomposition is insignificant in the case of water but very relevant with certain substances, such as carbon dioxide, that absorb heat in this way.

Smothering

If the oxygen supply to the burning material can be sufficiently reduced, burning will cease. The general procedure is to prevent fresh air from reaching the seat of the fire, allowing the combustion to reduce the oxygen content in the confined atmosphere until it extinguishes itself, for example by:

• Snuffing out candles
• Smothering a pan with a fire blanket
• Wrapping a person in a fire blanket
• Applying a blanket of foam over the burning surface, thus separating the fuel from the air

Smothering can also be achieved by removing the oxygen in the atmosphere, thus extinguishing the fire, for example, by:

• Introducing carbon dioxide (CO₂) to the immediate vicinity of the fire
• Introducing an inert gas to the immediate vicinity of the fire, such as through systems installed to protect computer server rooms

Starvation

In some cases, a fire can be extinguished simply by removing the fuel source. This may be accomplished in a number of ways, such as stopping the flow of liquid or gaseous fuel, removing solid fuel in the path of the fire or allowing the fire to burn until all of the fuel is consumed.

Fires can be starved of fuel by removing potential fuel from the vicinity of the fire, for example:

• Back burning forestry fires
• Draining fuel from burning oil tanks
• Removing cargo from a ship's hold
• Creating firebreaks in peat, heathland and forest fires
• Removing vehicles in the proximity of the fire
• Creating firebreaks in thatch roofs
• Removing tyres not affected by the fire from a tyre dump

Interrupting the combustion process

Dry powder, Bromochlorodifluoromethane (BCF) and other halon extinguishers work by releasing atoms that interrupt the chemical chain reaction. They also create an inert gas barrier.

General safety instructions for construction work

Safety oath 

I solemnly promise that I will do everything possible to prevent accidents, and occupational diseases, and to protect the environment, in the interest of myself, my family, my society and the nation.

 

1.  Always wear helmet and shoes in the workplace, always keep the helmet chin strap on.

 2. Do not do any work without safety equipment.  Obtain the necessary safety equipment from a supervisor before doing any work.  Follow the instructions of the supervisor.

3.It is strictly forbidden to put loose wire in any electrical socket.  Do not do any electrical connection without an electrician.

4.Don't stand under high-hanging items.

5.Do not jump in any moving vehicle. Never set foot on the area around the tires to climb. Use the ladder attached to it. Do not stand behind any moving construction machine. And do not rest in the shadow of any machine. Always be aware of the danger of being crushed by a machine while walking or reversing.

6.Always keep your work place clean and do not spread dirt.  Keep separate all waste  Sach as general waste , hazardous waste, food waste ,wood waste , concrete waste etc

7.While placing the pipe, the pipe does not roll, so that it should be fitted with a choke. When removing the sling, stay on the side of the pipe, not in front of it.

8.When making freight( temporary working platform) after lifting the pipe, first clamp it, only then open the rope.  So  that no one gets hurt if the pipe falls.  The person giving the pipe should also take care of this

9.When concrete with a bomb placer, use a rope to guide the hose of the boom placer.  Do not guide by holding with your hands.  There is a risk of shock and fall.

10.When stacking pipe or spool, provide adequate support near the bend/elbow so that the pipe or spool does not roll/topple.

11.While pulling a pipe or spool on a pipe rake, never stand in front of it. There is a risk of injury by rotating the pipe.

12.When working around electrical wires, always keep a safe distance from them.