Client Background
The client is a pharmaceutical manufacturer. They required a DSEAR risk assessment as the powdered API product was capable of forming flammable dust clouds.
Client Problem
The fine powder had a low minimum ignition energy and was also electrostatically insulating, so capable of accumulating charge.
Charge accumulation is enhanced in the high shear micronizing environment.
Equalisation of this charge could ignite a dust cloud. The client’s main question was whether nitrogen inerting or any other preventative measures were required
Client Objectives
Understand what precautions are required in specific situations.
Insights and results
Sigma-HSE found that
Since the powder is electrostatically insulating and subjected to high shear, the particles are likely to become electrostatically charged.
If this charge is equalised to a metallic component that is electrostatically isolated from earth, there is concern that the dispersed powder may ignite.
If processing in air, the equipment will need to be ATEX rated with explosion mitigation.
Rigorous earthing is also required. Very small batches may continue in non-ATEX equipment if operators are not present and the room is capable of withstanding an explosion.
Recommendations
Nitrogen inerting is in line with the DSEAR control hierarchy to prioritise the elimination of a flammable atmosphere before attempting to avoid ignition sources.
This inerting needs a mechanism to ensure the oxygen concentration is below the limiting oxygen concentration (LOC). Sigma-HSE has a laboratory to measure this.
Outcome
Customer saved financially as we were able to specify a batch size and procedures that were acceptable in the existing equipment.
