Wiring Systems - 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.
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, we have 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 installation standard IEC 60079-14 addresses "cold flow" in Clause 9.1.3.
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.
