The following is a 5 step risk assessment process:
Step 1: Identify the hazards
Compile a list of all materials in your factory that may create a dust cloud even those that might emit the dust accidentally. Identify the explosive materials using Safety Data Sheets, published explosibility data or dust testing.
Conduct explosibility classification tests on the remaining materials to prove whether they are flammable or not.
Consider sources of ignition, these might include:
- Electrical energy; short-circuit, lighting devices, electrical arc, electromagnetic radiation. Earth fault, loose contact, induction heating, overload leading to temperature rise, resistive heating, induction heating, and connection to an inappropriate electrical supply.
- Heat energy; open fire or flame, hot work, heating installations, intense radiation sources, laser, smoking, internal combustion engines.
- Chemical energy; runway exothermic reaction, heat sensitive materials such as thermite reaction sparks and pyrophoric substances.
- Mechanical energy; compression including shock waves and adiabatic compression, friction, grinding, impact and ultrasonic.
Step 2: Identify who might be harmed
In the event of an explosion, will it spread to the other parts of your facility (cause a secondary explosion) or will it be confined to the vessel? Will the explosion cause a fire?
Step 3: Check all the risks and decide on the right precautions
A dust explosion is devastating and leads to serious injuries, deaths and facility damage leading to long-term loss of production. Therefore, steps must be taken to prevent an explosion from taking place or mitigate its effects.
Preventing an explosion
Substitute flammable materials with non-flammable ones.
Do not allow the formation of an explosive atmosphere. This may be reduction of oxygen (inerting) or controlling the dust levels. Also, check dust suppressed materials by taking steps such as using oil additives to stop the dust from forming. Use screw elevators instead of belt and bucket elevators as they don’t produce internal dust clouds.
In some cases, it is best to stop using a particular equipment or stop all operations until a safety issue is fixed.
- Cut the quantity of dust cloud to a minimum
- Get rid of the sources of ignition
- Ensure that all workers have protective equipment
- Offer adequate training for all employees
- Maintain the work processes in a well-organized state
Install adequate explosion relief that discharge to a safe area. Alternatively, you can use flameless explosion vents.
- Install explosion containment
- Install explosion suppression
- Install explosion isolation equipment
- Record your findings and implement them to the fullest
Step 4: Record your findings and implement them
The risk assessment file that you share with the right factory staff should show that:
- A proper check was made.
- You considered who might be affected in the event of an explosion.
- You have checked and dealt with the hazards including the number of people who could be involved.
- Reasonable precautions; remaining risk should be low; everyone was involved.
Step 5: Review the risk assessment and update where necessary
Every change made in your factory should be documented and assessed with its effect on risk assessment. This includes physical changes such as change of material or installation of new equipment.