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Sat 19 May 2007 10:09 AM

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Cable movements

Wire mesh cable trays are slowly starting to gain popularity in the Middle East construction industry, but should more contractors be turning their attention towards this new technology? We investigate the potential benefits.

Cable trays can be broken down into three types: the solid bottomed variety, the ladder and the wire mesh or basket. In the last few years the development of the wire mesh has seen it gaining popularity in Europe and are now beginning to be applied in the Middle East market.

The choice of a cable support system still seems to be a fairly low priority in the planning of industrial, commercial and residential buildings in the region. According to manufacturer Cavotec, solid cable trays command around two-thirds of the market within the UAE. "Only around 5% of the market is wire mesh tray, with the remaining 27% going to the cable ladder system," says Cavotec chair Thomas Widegren.

On first appearance the solid tray looks stronger and more reliable, and some engineers still prefer it to its more modern counterparts. "As an engineer I prefer to use the solid trays because I think that they are sturdier," explains Jim Graham, area manager of distributor R & M Electrical. "They can hold the weight of the cables more comfortably than the wire mesh variety."

This view might make it difficult for the wire mesh tray to gain popularity in the region argues Danish Subzwari, director of Sreps, the Middle East distributor of Spanish firm Pemsa's wire mesh cable trays. "There is a perception issue here that wire mesh is weak and it will break when you run power cables in it," he says. "The working load of wire mesh and solid trays are similar. The difference is if the load rating is exceeded the wire mesh will sag, whereas the solid tray will crack." This is especially relevant at a time when the cost of steel is forcing some manufacturers to reduce the thickness of their solid tray products.

As much less steel is used in the manufacturing of wire mesh cable trays they are a lot lighter and as a result easier to install. "Weight is a big factor when you are planning a building," stresses Widegren. "You don't want a building that carries too much weight. In Dubai they are using modern types of scaffolding, so why not use more modern types of cable tray."

Davish Puthen Veettil, sales and technical support of French manufacturer Legrand, which also owns the Cablofil brand, stresses the wire mesh's inevitable rise will be down to the ease of its installation. "The wire mesh system is gaining ground because it is so much easier to install," he insists. "The system is connected together through unbolted couplers which just snap together, so there is no need for screws, washers or bolts."

The wire mesh system also requires less line items such as T-bends and intersections as it can be bent in most directions by hand. Cutting through the tray is an easier task also, requiring only a pair of handheld wire-cutters. As a result, health and safety issues are reduced as there is no need for power tools for cutting or for hot welding on site.

Cables can also be tied to the mesh system as tie wraps can be fitted with ease from below the installation. The weight of the mesh system and its simple jointing characteristics also leads to a reduction in installation time and allows for quick and easy removal for maintenance or replacing sections.

"It can take up to half the time to install the wire mesh than the solid trays," says Widegren. "And you use less staff to install them, which results in increased profits and productivity. The solid tray may be cheaper to buy upfront, but it's false economy because it requires more time to install and more operatives to do it. The cost of installing a cable system into a building is high, but the cost of the equipment in comparison is relatively low. It's great if you can cut this by reducing the man-hours."

At the moment the wire mesh system is proving popular in the Middle East food production industry due to hygiene issues. "There are a lot of hygiene issues in food manufacture and you have to wash down the trays every day," explains Subzwari. "With the solid bottom trays there is too much water sitting there once you've finished cleaning it, whereas with the mesh it just drips down. Also it is more difficult for vermin to manifest themselves in the mesh system. This is why the mesh system is also proving to be a popular choice in hospitals."

According to Puthen Veettil an important issue to think about when installing cable support systems is heat exchange. This is especially important in hot desert regions like the Middle East. "The metal trays can get very hot," he says. "With the wire mesh system you have less transfer of heat as there is less metal." As a result, smaller and more efficient cables can be used.

The problem of electromagnetic interference from power cables reducing the performance of data cables is another issue that should come to mind when installing cable trays. Using a wire mesh system with low-impedance couplings and a continuous metallic divider lessens the interference and reduces the distance of separation needed between the cables.

The only major disadvantage Subzwari can see in using the wire mesh system is its lack of physical protection. "When running a cable on a tray some people want it to be protected on all sides, so that the cables are more protected from possible puncture. Clearly you don't get this with the wire system," he says.

It seems that the cheaper upfront cost of the solid cable tray is still proving to be a more attractive option in the Middle East, with many players in the construction business using it in preference to the wire mesh variety. At present the wire mesh is being used primarily to support data cables and very little else. "We need to change people's perceptions of wire mesh cable trays," says Subzwari. "If something is working well then people don't like to change, but they must realise that they can gain so much, most notably in the way of cost and time savings."

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