Presentation of most common types of protection


A flameproof enclosure is an enclosure in which the parts which can ignite an explosive gas atmosphere are placed and which can withstand the pressure developed during an internal explosion of an explosive mixture, and which
prevents the transmission of the explosion to the explosive gas atmosphere surrounding the enclosure.
A flameproof enclosure must be able to fulfil three criteria:
• Contain an internal explosion without permanent distortion.
• Guarantee that the explosion cannot be transmitted to the surrounding atmosphere.
• Exhibit a temperature at all points on the surface which is lower than the spontaneous ignition temperature of the surrounding gases or vapors.
There are 2 construction values which make impossible for an explosion to answer to the 3 criteria:
• the flange length (L)
• the gap (i)
These values depends of gas group and the authorized maximum gap depends on the flange length.
It is necessary to lubricate the thread and to ensure that at least 5 threads are engaged for metric thread and at least 3.5 threads are engaged for NPT threads.
Holes which are not used for cable entries must be blanked using the appropriate blanking plugs.
The equipment is supplied with the joint flanges lubricated. When the equipment is installed, the path must be lubricated to keep them in good condition. Use a non-hardening, anti-corrosive grease. (see technical note)
In order to successfully retain the flameproof character of the equipment:
• Care must be taken before starting up to ensure that all the screws for closing the covers and cable entries are firmly tightened and for GUB enclosure that the blocking device is well screwed.
• Modification of the original predrilled holes is prohibited.


Method of protection applicable to electrical equipment such as light fittings, sockets, switches, etc, which consists of preventing the occurrence of any accidental ignition.
The construction principles for increased safety « e » equipment are as follows:
• Use of high-quality insulation materials
• Specially dimensioned clearance and creepage distance
• Electrical connection which cannot become loose
• Minimum IP54 weatherproof protection of the enclosure
• Respect of the temperature classes
• Conformity of cable entries
• Labelling.
These are created by screwing the cable gland directly onto the enclosure or, for untapped holes, by fixing with a locknut. Holes which are not used for cable entries must be blanked using the appropriate blanking plugs.
The equipment has a protection index of at least IP 54; it is therefore important to ensure that the weatherproof seal is in good condition when the product is installed.
Defective seals must be systematically replaced.
It is important to be sure that the gasket is well positioning for the plugs and sockets and for all the luminaries before connecting the male and female parts (for plugs and sockets) and before closing the light transmitting part of the lighting fixture.
For the connection, all technical note or instruction sheet shall be followed.


Equipment excepted Ex d enclosures have a combined protection type « d » and « e » technologies are the most commonly used.
Certain appliances such as power sockets, lampholders, etc, whose design creates arcs and sparks in normal operation, cannot be produced with protection mode « e » only.
• The part where the electric arc is produced is enclosed in a small flameproof chamber.
• The connection terminals are « e » increased safety.
• The assembly is mounted in an « e » increased safety enclosure.