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
List of ignition sources

Bulk Solids Handling Safety
# Dust explosion physical properties # MIT - Minimum Ignition Temperature of dust # Dust explosion venting
# Dust explosion isolation

1. Introduction

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

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

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