Wiring Systems CENELEC And IEC
Cable systems and accessories should be installed in positions that prevent them from being subject to mechanical damage, corrosion, chemical attack, heat and other detrimental environmental conditions. Selection of the wiring system and cable type must consider these influences and where exposure to such conditions are unavoidable, protective measures such as minimising the risk of mechanical damage by the use of appropriate armoured cable types should be considered.
The connection of cables and conduits to the electrical apparatus must be in accordance with the requirements of the relevant type of protection and installation rules.
CENELEC and IEC Wiring Methods
With the introduction of cables incorporating new construction materials and especially cables with fire retardant or fire resistant properties such as cables complying with IEC 60331 and IEC 60332, cables may exhibit "cold flow" characteristics. "cold flow" is a term used for thermoplastic materials that flow when subjected to pressure at ambient temperature. These "cold flow" characteristics could have adverse effects on the protection of the apparatus. A suitable cable gland should be used that does not incorporate displacement / compression seals that act upon the part(s) of the cable having cold flow characteristics.
To overcome this problem, Hawke has developed Cable Glands that incorporate diaphragm seals that act upon the "cold flow" cable sheath without compressing or damaging the cable. A typical cable gland incorporating displacement/compression seals and a Hawke 501/453/Universal cable gland incorporating a diaphragm seal are shown below.
No cable damage due to Hawke 501/453/Universal diaphragm seal cable gland design.
Cable damage as found with cable gland designs incorporating compression / displacement seals.
The IEC and CENELEC installation standards, IEC 60079-14 and EN 60079-14 address "cold flow" in Clause 9.1.3.
Wiring Systems CENELEC And IEC
Wiring Methods For Type Of Protection ‘d’ - Flameproof Enclosures
The cable entry device e.g. cable gland, must comply with all the requirements referred to in the appropriate standard, be appropriate to the type of cable, and maintain the integrity of the equipment. Where Cable Glands enter flameproof enclosures, the cable gland / cable system assembly must comply with the following.
The first and most important criterion is that the thermoplastic, thermosetting or elastomeric cable is substantially compact and circular, has extruded bedding and the fillers, if any, are non-hygroscopic. Should the cable not meet with any of these criteria, a barrier cable gland, e.g. a Hawke ICG 653/Universal cable gland that incorporates compound filled seals around the cables individual conductors or other equivalent sealing arrangements must be used. The reason being is that the products of an explosion within the equipment may enter into the cable through its voids or interstices and cause ignition of the potentially explosive atmosphere surrounding the cable or inside the equipment the cable is connected to.
Cable glands may also be designed, tested and certified for use with a particular cable construction type e.g. for use with trace heating flat form cable types. The cable gland approval certificates, if applicable, will refer to the appropriate cable type description.
Cable glands may also be designed for use with a particular cable construction and be tested and certified with the equipment. Reference to these cable gland types will be given in the equipment approval certification documents, if applicable.
The IEC and CENELEC design, selection and installation standards, IEC 60079-14 and EN 60079-14 offers guidance on the selection of flameproof cable gland types.
Where cables enter flameproof equipment directly, they should comply with the following:
a) Application:
An enclosure in Zone 1 or 2, Group IIA or IIB that contains terminals only or an enclosure that does not contain equipment with an ignition source such as arcing or sparking devices (e.g. relays, contactors, etc) or equipment that in normal operation will not cause temperatures that can cause ignition.
Cable Gland Selection:
A certified cable gland suitable for use with the particular type of cable and incorporating a sealing ring(s) that acts upon the appropriate cable sheath(s), is permitted for use.
b) Application:
An enclosure in Zone 1 or 2, Group IIC with an enclosure volume greater than 2-litres, that contains terminals only or an enclosure that does not contain equipment with an ignition source such as arcing or sparking devices (e.g. relays, contactors, etc) or equipment that in normal operation will not cause temperatures that can cause ignition.
Cable Gland Selection:
A certified cable gland suitable for use with the particular type of cable and incorporating a sealing ring(s) that acts upon the appropriate cable sheath(s), with an uncompressed length of 20mm for circular cables with a diameter not greater than 20mm and 25mm for circular cables with a diameter greater than 20mm, is permitted for use.
c) Application:
An enclosure that contains equipment with an ignition source such as arcing or sparking devices (e.g. relays, contactors, etc) or equipment that in normal operation will cause temperatures that can cause ignition in Zone 2, gas group IIA or IIB.
Cable Gland Selection:
A certified cable gland suitable for use with the particular type of cable and incorporating a sealing ring(s) that acts upon the appropriate cable sheath(s), is permitted for use.
Wiring Systems CENELEC And IEC
d) Application:
An enclosure that contains equipment with an ignition source such as arcing or sparking devices (e.g. relays, contactors, etc) or equipment that in normal operation will cause temperatures that can cause ignition in Zone 1, gas group IIA or IIB and an enclosure volume greater than 2-litres.
Cable Gland Selection:
A certified cable gland suitable for use with the particular type of cable and incorporating compound filled seals around the cable's individual cores or other equivalent sealing arrangements that seal around the cable's individual cores.
e) Application:
An enclosure that contains equipment with an ignition source such as arcing or sparking devices (e.g. relays, contactors, etc) or equipment that in normal operation will cause temperatures that can cause ignition in Zone 1, gas group IIA or IIB and an enclosure volume less than 2-litres.
Cable Gland Selection:
A certified cable gland suitable for use with the particular type of cable and incorporating a sealing ring(s) that acts upon the appropriate cable sheath(s), is permitted for use.
f) Application:
An enclosure that contains equipment with an ignition source such as arcing or sparking devices (e.g. relays, contactors, etc) or equipment that in normal operation will cause temperatures that can cause ignition in Zone 1 or 2, gas group IIC.
Cable Gland Selection:
A certified cable gland suitable for use with the particular type of cable and incorporating compound filled seals around the cable's individual cores or other equivalent sealing arrangements that seal around the cable's individual cores.
Exceptions:
- Cable gland types specified in the equipment documentation and incorporating sealing devices appropriate to the cables used.
- Cable gland types tested and certified with a particular cable construction type.
Wiring Methods for Type of Protection ‘e’ - Increased Safety:
The cable entry device, e.g. cable gland, must comply with all the requirements referred to in the appropriate standard, be appropriate to the cable type and maintain the type ‘e’ integrity of the equipment.
A minimum ingress protection rating of IP54 is required for increased safety equipment. To meet with this requirement it may be necessary to provide a seal between the cable gland and the equipment, for example, by the use of a sealing washer or thread sealant. Where Cable Glands are fitted into non-metallic enclosures, metallic enclosures with a painted type finish or enclosures with non-threaded clearance holes, additional ingress and earthing / bonding considerations may be necessary. Please visit our accessories page for solutions to these additional considerations.
