Construction and Operation Of Fire Extinguishers

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.

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