Avoiding a new ATEX dust up

While traditional ATEX industries such as petrochemical processing facilities are used to conformity, motors without correct certification are likely to be used in the recently defined ATEX zone 20 to 22 dust conditions, warns Dave Hawley, general manager of Deritend’s Wolverhampton motor repair and rewind workshops:

Many more process companies are now subject to ATEX regulations for the first time, due to the inclusion of dust laden atmospheres. These operators may be aware that explosions and fires caused by dust can be equally as devastating as those caused by explosive gases and vapours, but not what constitutes a risk and how to address it.

Compliance as far as dust and electric motors are concerned is actually relatively simple and the motor parameters required are not extreme, but there is a genuine need to know within industry. The previous regulations for explosive atmospheres did not account for the risk of explosion created by dust.

There have been several large explosions investigated in recent years in areas such as crop storage, food processing, coal processing and plastics that are now attributed to dust. Both atmospheric and settled dust can pose a problem and are now included in the new regulations.

Most industries used to dealing with explosive gases and vapours - typically from the petrochemical sector - are unlikely to have to make many, if any, changes as a result of the new directives. Companies in this sector will also know what type of new motor they need to use and that it is advisable for an approved repairer to be used to certify a repaired motor.

Companies not using motors that have been certified by the supplier or repairer are however liable should anything go wrong, under ATEX 137. Industries such as paper, processing, food preparation, textiles, woodworking and companies supplying machines into these sectors however, are likely to be included for the first time and require the most information.

Zones

Zone classification is the responsibility of the company on whose premises machinery is operating, i.e. the employer. It is also the responsibility of any company manufacturing machinery or repairing machinery that may create a risk or is designed to be used in a risk area.

Classification depends on the type of hazard present and the duration that machinery is exposed. Explosive gases such as hydrogen and vapours produced by petrol for example are zoned 0, 1 or 2 based on the frequency of their presence and their concentration.

Dust laden atmospheres created by activities such as composite woodworking and flour production are zoned 20, 21 and 22 based on the level of exposure. Settled dust is also included, which, depending on the type and amount can fall into any of the three categories.

What to look out for

Areas to look out for, where motors are at risk of causing a problem in the new dust zones are: conveyors, mixers, extractors, fans and pumps. Atmospheric dust is the most dangerous, something as simple as flour can cause powerful explosions. Extraction equipment should be used and motors working in this environment require a higher level of enclosure sealing of IP65 and a controlled maximum surface temperature of 125 °C.

Settled dust is a wider risk than atmospheric dust and tends to cause fires started by excessive heat, the smouldering temperature of common dust (i.e. not explosive chemical compounds) as varied as cocoa or paper is generally over 200 °C and so motor sealing to IP55 and a maximum surface temperature of 125 °C are adequate. It is important to note here that neither of these motors are EEx type rated motors and are less costly than such.

Motors must have full certification paperwork available from the manufacturer for inspection, when requested. Also motors must carry correct identifying labelling, including a re-assessed CE mark conforming to the new regulations. This is why purchasing a quality new motor from a knowledgeable supplier or a rewind from a reputable firm is essential for peace of mind and ultimately people’s safety. Older certified motors do not need to be re-certified, but the repairer does.

The DTI implemented the ATEX 95 directive under The Equipment and Protective Systems for Use in Potentially Explosive Atmospheres Regulations (EPS Regulations). The EPS Regulations have been fully in force since 1st July 2003. The date for actual conformity then - the date when product manufacturers or those taking responsibility for certification of supplied equipment can be held legally responsible for accidents due to non-conformity with the new directives, was back in 2003.