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COMBUSTIBLE METAL DUST CLEANING & COMBUSTIBLE METAL DUST HAZARD ANALYSIS

Removing Titanium and Aluminum Combustible Dust from Aerospace Facility

Oil Immersion Explosion Proof Vacuums Removing Titanium and Aluminum Combustible Dust from Aerospace Facility

Remtech has extensive experience with metallic dust hazard analysis and cleanup proceedures to identify, prevent and remove metal dust hazards that follow NFPA 484, 654, and 652 guidelines. Metal dusts are some of the most hazardous explosive dusts.

According to a 2018 report from the Chemical Safety Board (CSB), over the previous eleven years, there were 59 fatalities and 303 injuries associated with 105 combustible dust incidents. The vast majority of the incidents occurred in the food products, metals, and lumber and wood products industries.

Dusts, fines, and powders of combustible metals present an explosion hazard, especially if suspended or disturbed in confined spaces. Dust, fines, and powders of titanium present extreme hazards - Static electric charges can ignite some dusts and powders of titanium. Fires involving titanium cannot be extinguished unless they are placed in an inert atmosphere of argon or helium when they can only be controlled. Dust dispersed in air ignites violently and “explodes”. Small dust explosions usually dislodge dust accumulations leading to much larger secondary explosions. 1/32” of combustible dust accumulation over 5% of a room’s surface area is all that is required for a potential metallic dust explosion.

Titanium and Aluminum Flash Fire Caused by Improper Vacuum Equipment used by another Contractor at an Aerospace Facility (See Burn Marks on Wall Ledge)

Aluminum and Titanium Reactive Pairs Dust Accumulated on Overhead Structures at Aerospace Manufacturing Facility

Aluminum and Titanium Reactive Pairs Dust Accumulated on Overhead Light Fixture at Aerospace Manufacturing Facility

Bulk Removal of Aluminum and Titanium Dust with Anti-Static and Conductive Brushes to Prepare for Mineral Oil Immersion Explosion Proof Vacuuming

Dust Explosion Class

Deflagration Index, Kst Range

(bar.m/sec)

Explosion Hazard

0

1

2

3

0

1-200

201-300

>300

None

Weak to Moderate

Strong

Very Strong

DUST EXPLOSION CLASSES AND HAZARD RANKINGS

Dust Explosion Class 3: Dusts and Safety Measures

Dust explosion classes categorize materials based on their potential to ignite and cause explosions. Among these, Dust Explosion Class 3 represents the most hazardous types of combustible dust, with the ability to produce catastrophic explosions under the right conditions. Key materials and considerations for this class, emphasizing their characteristics, risks, and proper handling procedures are presented below.

Dust Explosion Class 3: Dusts and Safety Measures

Dust explosion classes categorize materials based on their potential to ignite and cause explosions. Among these, Dust Explosion Class 3 represents the most hazardous types of combustible dust, with the ability to produce catastrophic explosions under the right conditions. Key materials and considerations for this class, emphasizing their characteristics, risks, and proper handling procedures are presented below.

Class 3 Dusts: Thermites and Metal Dusts

Thermites, a combination of a metal powder fuel and a metal oxide, fall into Dust Explosion Class 3 due to their extreme reactivity. Common thermite fuels include:

Aluminum (Al)

Magnesium (Mg)

Titanium (Ti)

Zinc (Zn)

Silicon (Si)

Boron (B)

Paired oxidizers include:

Boron oxide

Silicon oxide

Chrome oxide

Manganese oxide

Iron oxide

Copper oxide

Lead oxide

Highly Flammable Metal Dusts (NFPA-484)

According to NFPA-484, alkali metals are among the most flammable dusts. Particularly hazardous examples include:

Aluminum (Al)

Magnesium (Mg)

Titanium (Ti)

Tantalum (Ta)

Niobium (Nb)

Zirconium (Zr)

Reactive Metal Pairs: Unique Combustion Risks

Certain metal pairs can autoignite without the presence of oxygen. These reactive pairs generate intense heat and form intermetallic compounds. Examples include:

Aluminum + Nickel (Al + Ni)

Zirconium + Boron (Zr + B)

Titanium + Carbon (Ti + C)

Silicon + Zirconium (Si + Zr)

Cobalt + Silicon (Co + Si)

These pairs present a significant hazard because their reactions are self-sustaining and nearly impossible to extinguish once initiated.

Unique Properties of Metal Dust Explosions

Metal dust explosions differ from organic dust explosions in several critical ways:

High Flame Temperatures

Metal dust flames can exceed 3,500°C—over 1,000°C hotter than organic dust flames.

Intense Explosion Pressure

Metal dust explosions produce higher maximum pressures and rates of pressure rise, along with faster flame speeds.

Challenging to Mitigate

The extreme heat and pressure make controlling these explosions more complex than organic dust explosions.

Aluminum Dust in Explosives and Propellants

Aluminum has long been a key component in explosives, pyrotechnics, and propellants due to its high energy release when reacting with oxygen. Key highlights include:

Reaction energy: 225 kcal per mole.

Aluminum-based propellants were utilized in NASA Space Shuttle boosters, offering significant heat release and thrust.

Comparative energy: 1 gram of aluminum dust has explosive energy comparable to 0.7 grams of TNT.

Safe Handling of Combustible Dust

Vacuuming combustible dust poses a fire and explosion risk due to static charges generated by particle motion. To mitigate these hazards:

Pre-Vacuum Cleaning

Remove bulk dust using conductive, non-sparking brushes and dust pans.

Specialized Vacuum Equipment

Use mineral oil immersion vacuums that are properly bonded and grounded. Equipment should be conductive and anti-sparking to prevent ignition.