An explosive combination

The complexity of meeting the ATEX requirements and conforming to its standards is not an easy task. This article is not meant to be used in isolation but as a starting point. Exact information on any precise requirements should be fully researched separately.

This new European directive, which came into effect from July 1 this year, deals with electrical, mechanical, hydraulic or pneumatic equipment in areas exposed to explosive atmospheres.

ATEX – from the French ATmosphere EXplosive or areas with explosive atmospheres – refers to two new EU directives relating to the danger of explosion within different areas. The first ATEX directive (94/9/EC) deals with the requirements pertaining to equipment used in areas where there is a danger of explosion.

The manufacturer has to fulfil the requirements and mark his products with the relevant approval. The second ATEX directive (99/92/EC) deals with the minimum health and safety requirements the user has to fulfil when working within areas where there is a danger of explosion.

An explosive atmosphere is an atmosphere that develops explosively because of changing surroundings or as a consequence of use. Explosive atmospheres consist of air and combustive material such as gases, vapours or dust in which the explosion could spread after ignition. Typical production sites where combustible dust is of major concern is in, for example, the handling of cereals, animal feed, paper, wood, chemicals, plastics and coals.

The directive covers a surprisingly large range of equipment and industrial applications. Broadly speaking these must comply in the following areas:

• safety equipment and safety systems exposed to explosive gases or dust,

• safety, control and adjustment devices, which ensure a safe operation of production material and control equipment,

• electrical, mechanical, hydraulic and pneumatic equipment including pumps and electric motors.

Companies that produce, use or distribute this kind of equipment must comply with the basic health and safety requirements contained within the directive. The directive does not have retrospective implications, however, pre-existing products maybe be subject to analysis. In case of defects such as wear, the old products must be replaced with equipment that complies with the directive. In addition, products that are specifically made for use in areas with the high explosion risk should only be marketed when they fully comply with the directive. The safety requirements within the directive imply pumps have to carry a clear indication of which equipment group and category they belong to and in what areas they can be used. To prevent explosion, the equipment user is required to:

• take all necessary technical and organisational precautions,

• make a complete estimate of any explosion risk,

• divide potential explosive risk areas into zones,

• indicate the danger zones clearly. The directive distinguishes between two types of explosive atmospheres – gas and dust. Areas within these two kinds of explosive atmospheres are each divided into three sub-zones.

Although the zones characteristics are identical for both gas and dust, their numbering is different, see table 1.Grundfos manufactures pumps with motors in categories 2 and 3.

The illustration in figure 1 shows the division of an area into zones dependant on the level of danger from explosion. In each of the three different zones, only a certain category of equipment, in this case motors and pumps, can be used due to the danger of explosion. It is the responsibility of the equipment user to define whether a zone is to be considered hazardous within the regulations as stated in the directive. If the user has any doubts about the definition of hazardous areas, they should take advice from a competent or recognised inspectorate.

Equipment and zones have to comply with the directive. The CE marking is proof the equipment is manufactured according to the basic requirements and assessment procedures that apply to every EU member state. Depending on whether you are the equipment manufacturer, user or service mechanic there are certain safety requirements that you must comply to.

Grundfos, as a manufacturer, is exclusively responsible for producing equipment that meets the requirement stated in the EU directive. It is the responsibility of the equipment user to inform Grundfos of what kind of equipment he needs, as to category (2G), temperature (125°C) and 2G/3G motor protection (Eexe II T3). In addition, the

equipment user has to use

the product according to the pre-defined zones and therefore must take any possible risks into account.

Likewise, the equipment user has a responsibility to ensure the equipment runs safely through continuous maintenance. As of July 2003 installations must meet the requirements stated in the directive. If the equipment user is also the manufacturer, the user must fulfil all the requirements for both.

Service mechanics are not covered by the directive 94/9/EC. However, service mechanics have to make sure the work they conduct meets the safety demands that apply for products and equipment so all safety issues are fully complied with. Notified bodies such as KEMA and PTB have the authority to issue qualification certificates for service mechanics as proof of their knowledge in this field.

The requirements of the directive are not entirely new to electric motors.

Previously, they were placed under the IEC60079 standard and under local standards around the world. The directive includes references to EN standards that contain the same requirements as the IEC60079 standard. The IEC60079 standard still applies to electric motors in other parts of the world.

Grundfos is in a position to comply with the directive, with its range of ATEX approved CR pumps and motors carrying the CE

marking (see figure 2) that indicates which explosion category the pumps are designed for use in. The CR range of approved in-line pumps includes the CR, CRI and CRN. This family of centrifugal pumps is suitable for a wide range of liquid transfer applications and have a excellent reputation for their inherent reliability and efficiency.

Grundfos’s Cratex family offers a wide range of pumps that can be used in a broad range of different industrial applications. Grundfos offers bespoke, custom-built solutions to suit the individually specified requirements.

The pump is then manufactured to these precise requirements and supplied with the relevant CE marking, which will be registered with a rec-ognised and notified body.