ATEX Compliant Milling Equipment

What is ATEX

How safe an ATEX-marked mill is, should never have to be questioned. With the guidance and certification from a European Ex-notified body, powder size-reduction equipment manufacturers can address certain ignition sources – like mechanical sparks in mills – and clearly outline Special Conditions of Use to ensure a safe engineered solution is supplied when milling powders.

The ATEX directive is 100% geared towards the avoidance of a dust or gas-based fire or explosion – potentially putting operators, equipment, and facilities at risk.

Ignition and hazard assessment – where it all begins

The “ATEX Directive” is comprised of two European Directives: 99/92/EC, known as the “ATEX - Worker Protection” Directive and the new 2014/34/EU Directive, known as the “ATEX - Equipment” Directive.

The ATEX “Worker Protection” Directive is directed at the equipment Owner. Under Article 4, the equipment Owner is obligated to assess explosion risks in their facility. This includes conducting a hazardous area classification also known as “Zoning” (see Table 1).

Equipment for Potentially Explosive Atmospheres (ATEX)

The Atex Directive for Equipment Owner - Working Protection

The first step to reducing the risk of a dust explosion in any milling operation is to identify all potential ignition sources; then determine if each ignition source is likely to be present during “normal” operation, during an “expected” malfunction or during a “rare” malfunction; and finally, identify the measures taken to prevent the potential ignition source from becoming effective.

In the case of a mill, there are four potential types of ignition sources: electrostatic discharges; hot surfaces; mechanical sparks; and electrical sparks.

* Table 1. Equipment Protection Level and Category for each Zone.

ATEX Directive for Equipment Manufacturers - Four Steps to Minimize Risk

To minimize risk when purchasing, commissioning and operating milling equipment with combustible powders, the following steps are imperative:

1. Know the Ignition Sensitivity of The Powder.
   
   Some powders are much more ignition sensitive than others, therefore two key parameters need to be known: the Minimum Ignition Energy with inductance (MIE1mH) and the Minimum Ignition Temperature of the dust cloud (MITcloud).
   
   
2. Review the EU Type Examination Certificate, Special Conditions of Use, and Residual Risks.
   
   When purchasing a mill, be sure to ask the manufacturer for the “Specific Conditions of Use” (or Restrictions of Usage), and any residual risks from the ignition hazard assessment. Ask if foreign objects have been considered in the risk assessment (Fig 1), and insist on seeing the ATEX markings on proposed mills, and the EC (or EU) - Type Examination Certificate for any Category 1 mill before purchasing.
   
   Fig 1: Screw embedded in the screen during powder processing in a conical mill
   
   
   The mill supplied should be able to list the various Restrictions of Usage based on the Mill’s Category and/or Zoning and the Protection Methods proposed. If the manufacturer is unwilling or unable to supply this information, it may be advisable to decline the purchase and contact an alternate mill vendor.
   
   
3. Decide if Inertion or a Pressure Shock Resistant Mill is Required.
   
   If small foreign objects cannot be excluded with 100% confidence for a mill rated for 1G or 1GD internal zoning, expert opinion agrees inert or PSR design the mill. Speak to our team about what Protection Methods and/or Restrictions of Usage are required for 1D, 2GD/3GD internal zonings.
   
   
4. Review the Instructions and Conduct Operator Training.
   
   Review all operating instructions and warnings in the mill’s manual and conduct training with the users and maintenance staff to ensure they understand what is required to safely operate and maintain the mill. If additional support is required, consult the mill vendor for available on-site training programs.