Extract From EN 60079-14 : 2008 / IEC 60079-14 : 2007
Installations In Hazardous Areas
1.0 Connections of cables to equipment
The connection of cables to the electrical equipment shall maintain the explosion protection integrity of the relevant type of protection.
Where the certificate for the cable gland has an ‘X’ marking, this cable gland shall be only used for fixed installations. If an additional clamping is required to prevent pulling and twisting of the cable transmitting the forces to the conductor terminations inside the enclosure, a clamp shall be provided and placed within 300mm of the end of the cable gland.
Where the equipment is portable only cable glands without ‘X’ marking shall be used.
Cable glands and/or cables shall be selected to reduce the effects of ‘cold flow characteristic’ of the cable.
Note 1: Cables employing materials which may exhibit ‘cold flow’ characteristics. ‘Cold flow’ in cables can be described as the movement of the cable sheath under the compressive forces created by the displacement of seals in cable glands where the compressive force applied by the seal is greater than the resistance of the cable sheath to deformation. Low smoke and/or fire resistant cables usually exhibit significant cold flow characteristics. Cold flow could give rise to a reduction in the insulation resistance of the cable and, where reasonably practical, efforts should be made to prevent this by selection of suitable cable glands.
Cable glands with tapered threads shall not be used in enclosures having gland plates with unthreaded entries.
Note 2: Tapered threads include NPT threads.
Figure 1 - Selection chart for cable entry devices into flameproof enclosures for cable complying with item b) of 2.2 Selection Of Cable Glands
It is important to read notes and 2.2 Selection before selecting appropriate cable gland for flameproof applications from Figure 1 below:
NOTE - Internal sources of ignition include sparks or equipment temperatures occurring in normal operation which can cause ignition. An enclosure containing terminals only or an indirect entry enclosure (see 2.1 General) is considered not to constitute an internal source of ignition.
Extract From EN 60079-14 : 2003 / IEC 60079-14 : 2003
2.0 Cable Entry Systems
2.1 General
It is essential that cable entry systems comply with all the requirements referred to in the equipment standard and documentation. Cable glands shall:
- Be appropriate to the type of cable employed;
- Maintain the type of protection; and
- Be in accordance with 9.3.10
Where cables enter into flameproof apparatus via flameproof bushings through the wall of the enclosure which are part of the equipment (indirect entry), the parts of the bushings outside the flameproof enclosure shall be protected in accordance with one of the types of protection listed in IEC 60079-0. For example, the exposed part of the bushings are within a terminal compartment which may either be another flameproof enclosure or will be protected by type of protection ‘e’. Where the terminal compartment is Ex‘d’, then the cable system shall comply with 2.2. Where the terminal compartment is Ex‘e’, then the cable system shall comply with 3.0
Where cables enter into flameproof apparatus directly, the cable system shall comply with 2.2
2.2 Selection Of Cable Glands
The cable entry system shall comply with one of the following:
a) Cable glands in compliance with IEC 60079-1 and certified as part of the equipment when tested with a sample of the particular type of cable.
b) Where a cable, in compliance with 1.0 (a) is substantially compact; a flameproof cable gland, in compliance with IEC 60079-1, may be utilized, providing this incorporates a sealing ring and is selected in accordance with Figure 1. Compliance with Figure 1 is not necessary if the cable gland complies with IEC 60079-1 and has been tested with a sample of specific cable to repeated ignitions of the flammable gas inside an enclosure and shows no ignition outside the enclosure.
c) Mineral-insulated metal-sheathed cable with or without plastic outer covering with appropriate flameproof cable gland complying with IEC 60079;
d) Flameproof sealing device (for example a sealing chamber) specified in the equipment documentation or complying with IEC 60079-1 and employing a cable gland appropriate to the cables use. The sealing device shall incorporate compound or other appropriate seals which permit stopping around individual cores. The sealing device shall be fitted at the point of entry of cables to the equipment;
e) Flameproof cable gland, specified in the equipment documentation or complying with IEC 60079-1, incorporating compound filled seals or elastomeric seals that seal around the individual cores or other equivalent sealing arrangements.
Extract From EN 60079-14 : 2003 / IEC 60079-14 : 2003
3.0 Wiring Systems
3.1 General
Cables and conduits shall be installed in accordance with Clause 9 of the following additional requirements concerning cable entries and conductor terminations.
Additional cable entry holes may be made into the enclosure providing this is permitted by the manufacturer’s documentation.
Note 1: Threaded holes in plastic enclosures should be at right angles to the face of the enclosure (due to the possible moulding methods for plastic enclosures, the wall of the enclosure may have draw angles). Surfaces with angles do not allow the gland and associated fittings inserted in the hole to fit square to the face, resulting in ineffective sealing.
Note 2: Taper threaded holes in plastic enclosures are not recommended because the high stresses created during sealing of these threads may fracture the enclosure wall.
3.2 Cable Glands
The connection of cables to increased safety equipment shall be effected by means of cable glands appropriate to the type of cable used. They shall comply with the requirements of IEC 60079-0.
Note 1: To meet the ingress protection requirement it may also be necessary to seal between the cable glands and the enclosure (for example by means of a sealing washer or thread sealant).
Note 2 - In order to meet the minimum requirement of IP54, threaded cable entry devices into threaded cable entry plates or enclosures of 6mm or greater thickness need no additional sealing between the cable entry devices and the entry plate or enclosure providing the axis of the cable entry device is perpendicular to the external surface of the cable entry plate or enclosure.
Where mineral-insulated metal-sheathed cables are used, the requirement to achieve creepage distances shall be maintained by using an Ex ‘e’ mineral insulated cable sealing device.
Threaded adaptors complying with IEC 60079-0 may be fitted into the cable entry holes to allow connection of the device or cable gland.
Unused entries in the enclosure shall be sealed by blanking elements, which comply with IEC 60079-0 and maintain the degree of ingress protection IP54 or that required by the location, whichever is the higher.
Acknowledgement
Extract from BS EN 60079-14 : 2008 reproduced with the permission of BSI under licence no. PD/1998 1818 and 1920. Complete editions of the standards can be obtained from www.bsi-global.com
