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Powder extinguisher

Information

Powder fire extinguisher is a solid substance in a powder state used in fire fighting. It is commonly known as: “dry powder”, “dry chemical powder”, “chemical powder”, or “polyvalent powder”. Its composition has a base of inorganic salts and additives.

Composition

  • Sodium bicarbonate.
  • Potassium bicarbonate.
  • Potassium chloride.
  • Urea-potassium bicarbonate.
  • Monoammonium phosphate.
  • Alkali metals.

Metal estearates, tricalcium phosphate, silicones and other products are added to improve the fluidity, hygroscopicity and electrical insulation of the final product.

General properties

  • Particle size less than 500 microns.
  • Zero toxicity, except where a massive discharge occurs which may cause respiratory problems and lack of visibility.
  • Poor conductor of electricity.
  • Can be used at temperatures below 60 ºC.

Fire extinguishing properties

Cooling
Absorbs a minimal amount of heat, with insignificant effects.
Suffocation
In the case of polyvalent ABC powder, upon decomposing due to the effect of heat from the fire, it produces metaphosphoric acid that separates the fuel from the oxidant, which is its most important fire extinguishing effect on fuels that produce embers when burning.
Inhibition
When the fire extinguishing agent comes into contact with the flames, it releases a series of compounds that react with the free radicals and stop the chemical reaction. This is the greatest effect obtained with BC powder.

Types of powder extinguishers

  • Conventional powder or BC powder for Class B and C fires. Composed by bicarbonates and sulphates.
  • Polyvalent ABC powder for Class A, B and C fires. Composed by monoammonium phosphates.
  • Special powders for suppression of Class D fires. Below are tables of these compounds.

Suitability of the different powders for the suppression or control of metal fires.

Suitability of the different powders for the suppression or control of metal fires.
Nature of powder Sodium Potassium Lithium Magnesium Aluminium Titanium Uranium Zirconium
Talc       *C        
Graphite * * * **(Dry) * ** ** **
Dry Sand         *C      
Iron dust       *C        
Sodium chloride ** **   *        
Soda ash (sodium carbonate) ** **            
Lithium chloride     **          
Zirconium Silicate     **          
Dolomite (calcium magnesium carbonate)            **C(Dry)   **C(Dry)
*
Acceptable
**
Suitable
C
For fire control only

Suitability of the different powder mixture preparations (patented) for the suppression or control of metal or alloy fires.

Suitability of the different powder mixture preparations (patented) for the suppression or control of metal or alloy fires.
Powder name and composition Na K Li Mg Al Ti U Zr Hf Th Pu Ca
G-1 "Pyrene" powder (Graphited foundry coke and organic phosphate) ***(1) ***(1) ** *** *** (in powder) ** ** **C ** ** ** **
"Metal Guard" powder (Graphited foundry coke and organic phosphate) **(1) ***(1) ** *** *** (in powder) ** ** **C ** ** ** **
"Met-L-X" powder (Sodium chloride, tricalcium phosphate, metal estearates and plastic thermal powder) **(1) **(1) ** *** ** (in powder) ** ** **C        
"Na-X" powder (Sodium carbonate, fluidifying additives and anti-hygroscopic agents) ***(metallic)     **C (in splinters)       **C (in splinters)        
"Lith-X" powder (Graphite and fluidifying additives) **(1) *C *** * (in splinters)       * (in splinters)        
"Pyromet" powder (sodium chloride, diammonium phosphate, protein and water-repellent and fluidifying agents) **     ** (in powder and splinters) ** (in powder and splinters) **   **       **
"TEC" powder (potassium, sodium and boric chlorides) *** ***(1) (1)       *       *  
*
Acceptable
**
Suitable
***
Very Suitable
C
For fire control only
 
 

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