Technical articles

 

ATEX device’s manufacturers use different types of protection to achieve a certain EPL. These methods of protection are constantly evolving both technical and regulatory. In any case, the most used are those that have established themselves historically.

The in-depth knowledge of the protection methods is the prerogative of the device’s manufacturers and of the notified bodies who must verify the requirements. However, understanding some aspects of the protection modes is an essential requirement for a successful installation.

Before going into the details of the most used methods of protection, it is necessary to deepen some basic concepts which, as we will see, will return to the legislation on several occasions.

We can start by understanding the meaning of the word explosion.

 

Each equipment that must be installed in an ATEX classified area must have a certain level of protection, indicated in the legislation with the acronym EPL (Equipment protection Level).

The level of protection is obtained by applying technical regulations that define the protection methods.

The in-depth knowledge of the protection methods is the prerogative of the equipment’s manufacturers and of the notified bodies who are called to verify the requirements.

Among the various areas of application of the ATEX directive, the most widespread is the one concerning surface systems with the risk of the presence of an explosive atmosphere due to a mixture of air and flammable substances in the form of GAS or vapor. [1]

In this sector, installers and designers often ask themselves questions relating to the choice of the right electrical appliances to be installed on the plant site.

This choice depends on a series of parameters, among these we will deepen the probability that an explosive atmosphere can form (concept of zone) and the type of substances involved in this formation (concepts of GAS group and temperature class).

In the plant concept it has always been of primary importance the physical separation between safe area and classified area. This concept was applied in the electric energy transport systems by means of cables buried in sand bed and then derived to the user (an electric motor or a junction box or an end user) with the use of a conduit tube suitable for the insertion of electrical cables (Freez-Moon) free from internal ridges and terminated on the end user through a physical separation made with explosion-proof sealing device (for example a sealing fitting).

 

With the advent of the IEC/EN 61241-0 and IEC/EN 60079-0 standards, as well as the IEC/EN 60079-1 standard, changed the concept of cable entry in electrical and electronic equipment suitable for areas with danger of explosion, allowing to have the cable entry with appropriate sealing cable gland.