The law in a nutshell

The owner of an installation where flammable substances or gases can occur, is obliged to comply with ATEX153 (1999/92/EC). In short, this legislation states that the risk of explosion for employees must be acceptably small.

Places where explosive atmospheres may occur are divided into zones. In these zones apparatus should be used in accordance with the categories of ATEX114 (2014/34/EU). However, equipment is only considered to be such if it has its own intrinsic ignition source and fulfils an autonomous function. Also safety systems, meant to limit the consequences of an explosion, have to comply to ATEX114.

Deviations are only allowed if they are well-founded. Apparatus in service before 30 June 2003 does not have to be Ex. In both cases it is of great importance that explosion safety is demonstrated and guaranteed.

Internal zoning

The ATEX legislation does not specify whether the inside of an installation must be zoned. The ATEX guidelines state that internal zoning is not necessary, provided that a proper explosion risk analysis is carried out. This analysis must show which requirements must be imposed on equipment and whether protective measures are necessary. Equipment that is placed inside must, when an explosive mixture is possible, comply to ATEX114!

There are a number of exceptions to this general rule. For example, the device does have to comply with ATEX114 if it can cause an explosive atmosphere around it due to its design.

Systems from practice

A compressed air-cleaned filter is not a device, as it does not have its own ignition source. An own risk analysis is sufficient here. Since an explosive dust mixture may be created during any compressed air cleaning, sources of ignition must be avoided with a high degree of certainty. Electrostatic discharges, sparks or glowing particles from the outside are often difficult to exclude, which means that protection is usually necessary.

A screw conveyor does fulfil the requirements of a device. There is certainly a risk of explosive dust mixtures on the inside. When it concerns a well sealed conveyor it may be assumed that there is no interface with the outside. In that case ATEX114 is not relevant. The manufacturer or user must carry out a risk analysis to determine whether the product in question can be transported safely.

A pump placed in a non-zoned area can leak and still cause a zone 2 in the area. Externally this pump must then be Ex Cat. 3G. It is not up to the manufacturer to determine this zoning, but it is useful that the manufacturer takes this into account in advance.

In a sawmill, zones 22 have been defined locally because of layers of dust, which are removed regularly. In the zoned area, there are several woodworking machines such as a saw and a milling machine. These undeniably have mechanical and electrical ignition sources. An Ex execution is not relevant here, the explosion risk must be eliminated by taking the necessary organisational measures.

Conclusion

For the environment of installations, Ex devices are by definition mandatory if they are used in a zone.

Process-wise (internal), it is especially important that a good risk analysis be carried out. This will have to show where extra a measures are needed, these are preferably preventive systems but in many cases security is unavoidable.