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Dust explosions : Ignition sources of dust clouds

List of possible ignition sources of powder to be assessed in dust explosion risk analysis

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Section summary
1. What causes dust explosions
2. List of ignition sources

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Powder and bulk solids handling factories must be able to identify the potential ignition sources of dust clouds in order to prevent explosions. Keys infos on electrostatics discharges, mechanical sparks, open flames are given in this page and can be used in risk assessments.

1. What causes dust explosions

After defining the zoning of the process and the process area, a dust explosion risk analysis requires to review every source of ignition in order to identify risks that would be unacceptable and require action. The table below aims at summarizing those different sources of ignition to guide the engineer in his risk assessment.

2. Sources of ignition - causes of dust explosions

The table below gives an overview of the different sources of ignition of dust clouds. Clicking on the links in the 1st columns will give you more infos.

Ignition source	Definition
Electrical equipment	In case of malfunction, electrical equipment can generate electrical sparks energetic enough to trigger the explosion of a dust cloud Hot surfaces : For equipment generating heat, the maximum temperature must be lower than the temperature required to ignite dust layers or dust cloud
Electrostatic discharges	The study of risks related to electrostatic discharges must be subdivided by analysing the following phenomena : Electrostatic spark Brush discharge Propagating brush discharge Corona discharge Cone discharge (lightning type discharge)
Mechanical sources	Mechanical malfuntions can also lead to dust explosion if the energy released is sufficient. It can due to : Metal / Metal contact (impact) creating sparks Hot surfaces : metal rubbing increasing the temperature locally Note that an agitator for example can increase the temperature of a powder. It may be considered in equipment like mills or rotary sifters
Open flames	Works in the production area can be a source of ignition if it involves activities like welding or cutting