Cablofil Cable Basket - Dispelling the Myths

By Jonny Hewitt on 15th November, 2013

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Cablofil Cable Basket - Dispelling the Myths

Cablofil Cable Wire Basket Tray for LV HV Industrial Power Cables

While the advent of Cablofil steel wire tray cable management systems has revolutionised the way that contractors approach containment installations, a number of myths still surround the use of steel basket cableCablofil Cable Basket - Wire Cable Basket tray. Here, Paul Courson, UK managing director of steel wire tray specialist, Cablofil, discusses these misconceptions and outlines the evidence that dispels them.

Ask any contractor that uses a steel wire tray system routinely and they will tell you that they find it the quickest, easiest and most convenient cable management solution to install. Indeed, speak to installers about it and they are generally so enthusiastic that you’d expect to find steel wire tray installed in any and every environment for which it is suitable. However, not all in the electrical industry are convinced about the advantages of steel wire tray and often those specifying a job are not sufficiently convinced to change their tried and tested approach.

As it’s now over two decades since steel wire tray was firstCablofil Cable Basket - Wire Basket introduced to the UK, this reluctance to specify steel wire tray amongst some M&E consultants can be unfathomable to some contractors: but it is not simply based on habit and tradition. A number of misconceptions about steel wire tray persist, encouraging some specifiers to deem it unsuitable for some applications. While the quality and design of steel wire tray systems does vary, making specification of the right basket system critical to the installation’s success, the reality is that these misconceptions are precisely that: ill-conceived assumptions. Only by examining these myths and presenting the evidence that disproves them can we continue the culture change in the UK electrical industry that has seen growing acceptance of steel wire tray systems over the past 20 years.

If it Ain’t Broke?
The most fundamental misconception surrounding steel wire tray specification is that it’s not possible or is too difficult to change the specification. Often, experienced contractors can see that the use of steel wire tray would provide an end result equal or superior to alternative systems but don’t think that they’ll be able to convince the consultant to change the specification. This issue is particularly acute in situations where the original specification calls for the use of trunking as changing the specification for the cable management system will also involve changing the cable specification. However, as the team responsible for delivering the job on site, the contractor needs to be confident in putting across the case for a change of specification and the cost and speed of installation benefits offered by steel wire tray make a pretty compelling argument, particularly in these challenging economic times.

Certainly, there are many examples of changes in specification to steel wire tray cable management that have been driven by the contractor and the evidence highlighted below against some of the popular myths surrounding steel wire tray systems should provide ammunition to help encourage an open-minded approach.

Comparable Load Bearing
In many installations, while steel wire tray is specified for data and lighter small power cabling, the specification reverts to perforated steel tray for heavier power cables because specifiers are often unnecessarily concerned about the load bearing capabilities of steel wire systems. Again, it’s important to stress that all steel wire systems are different and the maximum load bearing capabilities of individual steel wire tray brands should be verified but, broadly speaking, many would be surprised to learn just how strong steel wire tray systems can be.

For example, the load bearing capacity for 300mm widthCablofil Cable Basket - Steel Wire Mesh Baskey Cablofil steel wire tray is 140kg/metre while for comparable perforated steel tray it’s just 110kg/metre. It’s clear from this simple statistic that steel wire tray systems can be suitable both for installations that require multiple cables to be loaded onto a single run of containment and for installations requiring heavier cables. In fact, high quality steel wire tray systems can handle the same cable loads as any perforated steel tray system or medium duty ladder.

Short Circuit Integrity
The common objections to the use of steel wire tray systems for power cable installations often also include the supposed threat to the system’s integrity should a short circuit occur. However, with a quality steel wire system this perceived risk is a complete fallacy and should not prevent specification of a suitable basket system.

To prove this point, Cablofil commissioned independent tests to demonstrate that a quality steel wire tray system will remain unaffected by a short circuit. The tests were carried out at a well-respected independent laboratory (DAMSTRA), in accordance with EN 50 368 (2003) standard and used Cablofil steel wire tray to demonstrate that a quality steel wire tray system has the mechanical resistance required to withstand the stress generated by a short circuit. The test rig comprising a three-metre length of 450mm steel wire tray with a support span of 1.5 metres was used, into which were placed three single conductor, 38mm power cables, attached at 600mm intervals using standard cleats. During the tests, this configuration was subjected to an initial short circuit, creating mutual electromagnetic repulsion between the power cables and the cable tray was then subjected to substantial mechanical stress for approximately one second. The process was then repeated to show that the steel wire tray was structurally intact and able to cope with another short circuit. Finally, further tests were performed in a damp environment to check whether the cables were fully intact. This test formula was carried out with three increasing levels of short circuit current: 70kA (equivalent to a repulsive force of 1300daN in each cleat); 100kA, (equivalent to a repulsive force of 2700daN in each cleat) and 130kA (equivalent to a repulsive force of 4500daN in each cleat).

Throughout all these tests the steel wire cable tray showed no permanent deformation as its mesh structure was able to absorb the physical stress generated by even the more significant short circuit current. The cables remained intact in their original positions and network availability was maintained, all of which proves conclusively that a high quality steel wire tray cable management system does not present any risk of structural damage to the network in the event of a short circuit.

Video : Ellis Patents Vulcan Cable Cleat Test - Trefoil Formation on Cablofil Cable Basket. Ellis Patents Vulcan VRT+ Stainless Steel Cable Cleats tested on 3 single cables in trefoil formation on Cablofil Cable Basket.

Hot-Dipped Alternatives
Even amongst those who accept steel wire tray’s merits relative to alternative systems in a standard commercial setting, there is still a tendency to dismiss for industrial installations. Here, while ladder is often required for some applications, in others where steel wire tray would be suitable it is often overlooked in favour of hot dip galvanised perforated tray.

In reality, even for heavier loads, a quality steel wire tray system offers a durable alternative to perforated steel tray along with numerous advantages. As a result, therefore, a hot dip galvanised steel wire tray system is a viable and often preferable alternative to a hot dip galvanised perforated steel tray for industrial applications. Both systems undergo rigorous chemical preparation before the steel is immersed in fused zinc at 450 to 460°C forming several layers of alloy deep within the metal which attach on the surface providing excellent and long-lasting corrosion resistance.

Both systems, therefore, are designed to cope with the demands of an industrial environment but a hot dip galvanised steel wire tray system is not only quicker, easier and more cost-effective to install, it is also more flexible: a clear advantage for industrial applications where installations are often complex and may require the cable management to be moulded to the contours of equipment. What’s more, the open mesh construction of a steel wire tray system ensures that cables are visible from the factory floor and easier to access by maintenance staff. In any environment that has a business critical requirement for all cabling to be fully operational on a 24/7 basis these features present significant advantages over more enclosed alternatives.

The vital consideration here is selecting a steel wire tray system that is proven in industrial environments and offers options within the range that have been specifically developed to answer the needs of an industrial environment, whether it be hot dip galvanised, stainless steel or an epoxy/custom coating finish.

Data Centre Concerns
While steel wire tray systems are under-specified in industrial environments, the lightweight, open structure of steel wire tray has made it a popular cable management choice for IT and data centre applications. Though commonplace here, however, its specification is not without controversy, with myths surrounding the use of steel wire tray often leading to labour intensive and costly over-specification of the job.

One of the enduring debates surrounds the use of matting which is laid inside the steel wire tray to prevent the perceived risk of damage to delicate data cables from the mesh structure of the steel wire tray. Again, Cablofil opted to commission independent tests to dispel worries about this phantom risk and these were carried out by Intertek Testing Services, a division of ETL, the world’s leading provider of testing, inspection and certification services.

The aim of the tests was to determine whether there were any advantages to including flat-bottomed supports in a steel wire tray containment installation for Cat 5e and Cat 6 cables. For the reliability test, 90 metres of Cat 5e and Cat 6 cables were tested with no load using both steel wire tray and a flat surface containment. The cables on both the steel wire tray and flat surface were then subjected to mechanical stress equivalent to the weight of 40 cables stacked together. The tests concluded that cables are at no greater risk of pressure marks in a steel wire tray installation without matting than they are if matting is installed. In short, the matting serves no purpose in protecting the cables.

Indeed, durability tests carried out at the same time concluded that the inclusion of matting in a steel wire tray installation in a data centre environment could actually be harmful to the cables as it inhibits the natural ventilation offered by steel wire tray’s open structure, thereby creating a danger of overheated cables!

Despite the evidence against the need for matting the debate rumbles on, as does the controversy about ‘zinc whiskers’. This phenomenon involves the possibility of microscopic particles of zinc (typically two microns in diameter) which separate from zinc-electroplated steel materials and could contaminate the atmosphere in a data centre environment. According to the theory, these particles, if not filtered out by the air handling units, could come to rest on an exposed circuit card causing a short circuit and equipment failure.

While the theory is based on valid reasoning, there are two key points to consider: firstly that the data cabinets and air handling units should prevent any zinc whiskers from damaging equipment (indeed, I know of no cases where there has been a problem caused by zinc whiskers); secondly that the cable management system is not likely to be the only zinc-electroplated material in the data hall. The actual risk, therefore, appears minimal, but any specifiers still concerned can still opt for steel wire tray if they select a powder-coated system, which will seal in the zinc-electroplating so that there can be absolutely no risk of zinc whiskers at all.

Clear Advantages
While steel wire tray has been around in the UK for more than 20 years and has been widely used and praised by contractors for much of that time, in many ways it is still the new kid on the block. It would appear that many of those who specify cable management are still sceptical that it can perform as well as its more traditional rivals or handle the same types of applications. Surely, however, by now, specifiers should be considering the advantages it offers and the genuine evidence in its favour as part of a best practice approach to selecting the right solution.

Video : Cablofil Wire Mesh Cable Basket Tray For Power Cables

 
Video YouTube : Cablofil Cable Basket - Wire Mesh Cable Basket Tray

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Category:  Cable Containment LV HV

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