BECKHOFF CX50x0 - Manual (Page 13)

Basic principles of explosion protection
CX50x0 units in potentially explosive areas 9
4 Basic principles of explosion protection
4.1 Why explosion protection?
The basis of an explosion is the presence of all three of the following factors:
 flammable material in a finely distributed form
 oxygen
 and an ignition source
An explosion can no longer take place if any one of these factors is absent.
Dealing with gases, dusts, vapors and mists is part of everyday work in many branches of industry, for example
in the petrochemical industry or in mills. In other areas these flammable materials are produced directly during
processing. Explosions can occur anywhere there due to the surrounding air and an ignition source.
Primary and secondary explosion protection measures have been developed in order to prevent explosions
and the resulting injuries to people and damage to materials and environment. Primary protective measures are
aimed at maintaining the surrounding atmosphere in a state incapable of explosion, while secondary protective
measures are intended to prevent the ignition of such an atmosphere. Secondary explosion protection is used
whenever a danger of explosion cannot be excluded despite primary protection.
WARNING
Observe the relevant standards and directives!
This chapter serves only as an introduction to “secondary explosion protection” and
does not claim to be complete. Therefore, knowledge of the contents of this document
does NOT relieve you from your duty to study all standards and directives relevant to
the use of electrical equipment in potentially explosive atmospheres.
In the ATEX directive 94/9/EC, the European Community has created the basis for binding uniform property
requirements with regard to the protection of systems, equipment and components against explosion, which
apply to use in Europe. The application of the directive 94/9/EC for explosion-protected applications has been
compulsory in the European Union since 1 July 2003.
Furthermore, this chapter serves as reference for the decoding of device markings.