When it comes to electrical and data cabling protection in hazardous areas, flexible conduit is a proven and cost effective alternative to specialist cables argues Tim Creedon, Sales and Marketing Director for Flexicon.
Obviously any electrical installation in an explosive area is a potential source of ignition. Assuming that the electrical equipment is correctly specified, it is important not to overlook any cabling that connects into it.
To meet Ex d requirements each individual cable needs a flameproof barrier gland, which adds both cost and time to the installation. You also need to consider that Ex d requirements insist that cables used in hazardous areas should be a considerably compact circular cable with extruded bedding and use fillers that are non-hygroscopic.
Assuming that you get the specification correct there are still other issues that you should consider. First is the number of cables that need terminating and where, which affects the size of the glanding panel space required, which in turn may impact on the control box enclosure size. You also need to consider how to protect the cables against mechanical damage.
Convenient and safe
The development of flameproof ATEX and IEC Ex approved barrier glands for flexible conduit helps to solve these issues since you can group several different types of cables together into one system. The conduit provides a secure means of containment for multiple cables with the added benefit of offering mechanical protection.
In addition, because the conduit encloses multiple cables within it there are fewer gland terminations, so you are less likely to compromise the enclosure’s integrity. This grouping not only saves time and money, but also reduces the need for specialist or bespoke cabling arrangements.
It also makes it simpler and faster to upgrade the installation in the future since you do not need to remove numerous barrier glands and cables. If sufficient space is available, you can route new cables through the conduit and only replace a single barrier gland. This is an even bigger benefit if space is at a premium and there is limited glanding space for the enclosure.
There are a number of ways of classifying protection techniques used to address hazardous zones. Most glands are classified as Ex d, Ex e or Ex t.
An Ex d classified gland forms a flameproof or explosion proof barrier, so if there was an explosion within the electrical equipment enclosure, then it would be contained within the enclosure. If something is classified as Ex d, then you can also use it for Ex e and Ex t applications. Similarly an EX e gland, which is used for increased safety and dust ignition proof applications, can also be used for Ex t applications.
When combined with liquid tight conduit, with an IP rating of between IP66 to IP69
k, then there is minimal or no chance of the explosive atmosphere in the form of gas, liquid or dust coming into contact with the cabling.
The basic role of any flexible conduit system is to protect cabling from potential hazards. This is even more important in hazardous areas since the potential risks could be catastrophic.
With this in mind the specifier needs to conduct a thorough risk assessment of all of the hazards faced by the cable protection, in order to select the most appropriate liquid tight conduit for the project.
If the build up of static charge is an issue for instance, then consider a conduit solution that features anti static properties. Check that these products have been tested and comply with clause 7.4.2 of EN60079-0.
Other things to consider may include crushing, movement and vibration, EMC screening, movement, vibration, abrasion, corrosion, chemicals and extremes of temperature. Note this is not an exhaustive list.
When considering hazardous area protection, it is important not to forget cable protection. With the development of flameproof barrier glands to Ex d standards and approvals for conduit systems, specifiers and installers can select a solution that best meets the needs for their situation. In most instances a liquid tight flexible conduit system used with a flameproof barrier gland will provide a safe, flexible and cost effective answer.
Telephone: 01675 466900
Fax: 01675 466901