Why an ATEX Conical Mill is Needed
“An explosive atmosphere is defined as a mixture of dangerous substances with air, under atmospheric conditions, in the form of gases, vapours, mist or dust in which, after ignition has occurred, combustion spreads to the entire unburned mixture.”1
Hence, the presence of gas or dust in certain atmospheres can potentially ignite. This is particularly true of grinding processes, where all 3 factors needed for a fire-risk are present.
- Oxygen: present in ambient atmosphere unless controlled (e.g. without inerting the process).
- Fuel: the dust or vapour from the material / environment (e.g. a combustible material with low MIE / MIT / LIT / KST / PMAX etc.).
- Heat: generated during the milling process (e.g. heat from the machine or energy created by the grinding / desizing of material).
Therefore, the process must be controlled in order to limit these factors which can lead to an explosion; hence the need for an ATEX conical mill.
A failure on milling equipment (or any other size reduction machinery) could result in excessive heat generation and has the potential to cause an explosion in a laboratory or manufacturing plant. As a result, the ATEX directives set out by the EU now include hazards from mechanical sources, such as mills.
The ATEX directives are primarily concerned with the safety of plant operators and sets out the minimum requirements for improving the health and safety protection of workers potentially at risk from explosive atmospheres.
The Responsibilities of the Supplier and the Customer
Manufacturers of milling equipment must ensure their products comply with the ATEX 95 equipment directive 94/9/EC given the information supplied by the customer on the ingredient properties. It is the customer’s duty to inform the supplier of the minimum ignition temperature of their products and the correct ATEX hazardous zone that the equipment will need to be compatible with (inside and outside the mill). The customer must also determine the explosive potential of their product by analysing and reviewing their own processing systems and configuration.
Using the information provided, the ATEX conical mill supplier can then design the equipment to meet the appropriate ATEX directive measures. The mill supplier is also responsible for advising the user of any precautions necessary to operate the mill safely.
With proper consultation between the supplier and customer, it is possible to design a safe system that fully complies with the complexities of the ATEX directives.
Hanningfield’s ATEX Conical Mill
The design and features of our Uni-Mill product range draws on many years experience working with customers to supply ATEX compliant milling equipment. Hanningfield’s ATEX conical mills are used in various industries including pharmaceutical, nutraceutical, food and nuclear.
To meet the level of hazard specified, our conical mills are customisable with special features as listed below.
> Temperature probes for monitoring
> Nitrogen purging
> Dust containment methods (e.g. a vessel with a HEPA filter)
> No metal-to-metal contact design to prevent sparking
> ATEX rated electrical equipment and accessories (e.g. motors, safety switches and control panels)
> Earthing clamps to ground stainless steel to stop the build-up of static electricity
The belt-driven and geared Uni-Mill machines can be made ATEX compliant. Both options also have external machine parts that are designed to keep the temperature of the mill and the material to a minimum.