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Is My Dust Combustible?

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When looking to protect your equipment against a dust explosion, it is critical to know the Kst value of your material. Kst is the dust deflagration index, and it measures the relative explosion severity compared to other dusts. This is a relative index, however, and any material with a Kst value greater than zero is considered to be at risk of an explosion. Other than silicon or sand, every kind of dust is potentially combustible to some degree.

Examples of Kst Values for Different Types of Dusts

Dust explosion class* Kst (bar.m/s)* Characteristic* Typical material**
St 0 0 No explosion Silica
St 1 >0 and ≤00 Weak explosion Powdered milk, charcoal, sulfur, sugar, zinc
St 2 >200 and ≤200 Strong explosion Cellulose, wood flour, polymethyl acrylate
St 3 >300 Very strong explosion Anthraquinone, aluminum, magnesium

The actual class is sample specific and will depend on varying characteristics of the material such as particle size or moisture. Source: http://www.osha.gov/Publications/3371combustible-dust.pdf * OSHA CPL 03-00-008 – Combustible Dust National Emphasis Program. ** NFPA 68, Standard on Explosion Prevention by Deflagration Venting.

Kst Values for Common Dusts:

Any value greater than zero is a potential explosion risk

Dust KSt Value Characteristic
Activated carbon 44 Weak Explosion
Aluminum grit 100 Weak Explosion
Aluminum powder 400 Very Strong Explosion
Asphalt 117 Weak Explosion
Barley grain dust 240 Strong Explosion
Bronze 31 Weak Explosion
Brown coal 123 Weak Explosion
Calcium stearate 132 Weak Explosion
Cellulose pulp 62 Weak Explosion
Cellulose 229 Strong Explosion
Corn 75 Weak Explosion
Charcoal 117 Weak Explosion
Cotton 24 Weak Explosion
Dextrin 106 Weak Explosion
Egg White 38 Weak Explosion
Epoxy powder 125 Weak Explosion
Epoxy resin 129 Weak Explosion
Flour, Bakers 4.3% Moist 112 Weak Explosion
Lead stearate 152 Weak Explosion
Magnesium 508 Very Strong Explosion
Malt dust 122 Weak Explosion
Melamine resin 110 Weak Explosion
Methyl cellulose 209 Strong Explosion
Milk powder 90 Weak Explosion
Paper tissue dust 52 Weak Explosion
Para formaldehyde 178 Weak Explosion
Peat 178 Weak Explosion
Pectin 162 Weak Explosion
Phenolic resin 129 Weak Explosion
Polyester 85 Weak Explosion
Polyethylene 134 Weak Explosion
Polyurethane 156 Weak Explosion
Rice starch 190 Weak Explosion
Silicon 126 Weak Explosion
Soap 111 Weak Explosion
Sodium ascorbate 119 Weak Explosion
Sodium stearate 123 Weak Explosion
Soot 26 Weak Explosion
Soybean flour 110 Weak Explosion
Starch, corn 202 Strong Explosion
Sugar 138 Weak Explosion
Sulfur 151 Weak Explosion
Tobacco 12 Weak Explosion
Toner 145 Weak Explosion
Wood dust 102 Weak Explosion
Wood Flour 205 Strong Explosion
Zinc 176 Weak Explosion

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One Response to Is My Dust Combustible?

  1. Pingback: Combustible Dust | News & Resources

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