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Cable management systems are still evolving

Sep 2012 Busbar & Trunking, Cable & Wire | Comments Off on Cable management systems are still evolving
Cable management systems are still evolving
 

Cable management systems address a wide range of applications in many sectors, and there has been increasing take-up by those installing not just electrical cable, but cable for data communications too. The basic types, however, are conduit, cable tray, ladder and ‘basket’, cable trunking, as well underfloor systems, as James Hunt finds.

One pressure within the electrical cabling sector is always to make installation easier, as lead times and money become ever shorter. For this reason, many recent cable management system developments have been towards providing products that are quicker, easier and cheaper to install and maintain.

The main types of cable management system available are conduit, trunking, busbar trunking, cable tray (steel, stainless steel, plastics and GRP), cable basket and cable ladder. We take a look at them here.

Conduit – This is less widely used today, but is still is ideal for many single-core conductor cable applications as it provides good protection from damage. Conduit, available black enamelled or galvanised steel tube, or in plastic, comes in standard diameters of 20, 25 and 32mm. Kopex is just one manufacturer that supplies pliable and flexible metallic and non-metallic conduit, as well as accessories. These include those designed for critical protection in hazardous areas.

Steel cable tray – This, available in light-, medium- and heavy-duty versions, is traditional and is suitable for carrying most cable types and is available in widths of 50‑900mm. The type provides good protection from damage whilst allowing reasonable ventilation. It comprises bent sheet perforated with a regular slot pattern to accept cable ties, banding and cleats with M6 fixings. Finishes are galvanised, coated or stainless steel.

Steel tray, which typically comes in standard lengths of 3m, is excellent where high strength is needed, sometimes only needing supports every 2-2.5m, rather than the 1-1.5m intervals that other types require. This reduces installation times.

Cable ladder – This type, also very traditional, is usually galvanised, though some is in stainless. The type is made from two sidewalls (sized 100, 125 or 150mm), between which are rungs spaced typically at 300mm centres. Widths range 150 to 1050mm (or more), and standard lengths are 3m or 6m. Cable ladder is suitable for long, straight cable runs, and heavy-duty ladder is one of the strongest forms of cable management, being able to carry significant loads over spans from 2-6m.

Cable basket – Wire mesh cable tray (‘cable basket’) has taken significant market share from heavy traditional steel tray because of its several clear advantages. It can be 25% quicker to fit because cable runs often follow a twisting undulating route. With conventional tray, this results in extra cost for all the necessary bends, risers and tees, or time wasting cutting. Wire mesh tray can easily be bent to shape, and all that is required is a spanner and a pair of bolt cutters. The tray is also better ventilated, so smaller cables can often be used, and cable faults are easier to detect and repair. Surprisingly, properly earthed wire mesh cable tray will protect cables from electromagnetic interference.

Trunking systems – Widely-used trunking systems comprise hollow box-shaped sections, usually each 3m long, with a removable lid, providing good cable protection. Many circuits can be contained in a single trunking and use dividers to provide for cable combinations. There are several sub-types:

Steel trunking – For decades the main cable management solution outside domestic installations, this is still quite heavily used. Steel trunking typically ranges in size from 50x50mm – 300x300mm and a wide range of fittings enables installers to secure it easily. Finishes are pre-galvanised and epoxy coated, and stainless steel trunking can be provided.

Aluminium trunking – Many aluminium systems, such as dado or perimeter trunking, are available to provide power and data to office desks. Aluminium trunking is stronger than some plastic types, is long lasting and provides good EMC protection. It can be supplied in various anodised colours – providing a highly attractive appearance, or can be powder coated. However, aluminium trunking can be relatively expensive and may not be as easy to install as the plastic variety.

Plastic trunking – PVC-U systems have fast gained popularity because of their lightness, ease of working, durability and excellent corrosion resistance. Such trunking is easier to fit to non-straight walls than metallic types and provides excellent protection, yet is compact and attractive, so is ideal for some domestic and many commercial applications. PVC-U perimeter trunking is designed for surface mounting as dados, skirting or cornices. PVC-U mini-trunking can be supplied flat or coiled, and is very easy to install. Heavier duty glass reinforced plastics (GRP) trunking for use outdoors combines zero corrosion with lightness.

Under floor trunking systems – These, for installation within floor voids or for burying into screeds, are used in the commercial sector for cost-effective cable management solutions with high design freedom. With screeded floors, cables are laid in trunking set into the floor to pre-wired floor boxes. Compartments enable segregation of electrical services into power, data and telecommunication. Floor boxes, power posts and poles provide service outlets, as do desk modules. Where there are many workstations together, a ‘hub’ arrangement, can be used, each feeding up to eight desks through outlets fed by flexible ‘umbilicals’.

However, screeded floor systems often lack flexibility for constantly changing office layouts, so raised floor systems have been gaining popularity. These are flexible, easing installation in both new builds and refurbishments, though they are not always suitable for older buildings.

Trunking systems generally are sized according to the number and size of cables to be contained – currently 40% of the trunking cross-sectional area maximum to avoid jamming, snagging or overheating. More than this and the trunking size needs to be increased.

Busbar trunking – This is an interesting alternative to hard-wired power and lighting circuits that may sometimes be cheaper overall. For example, a modern underfloor product is Crabtree’s Britmac Powertrack. This, designed primarily to power commercial and industrial applications, comprises fully enclosed, single-phase 63A busbar modules that assemble directly onto the base slab of a cavity floor using integral floor fixing brackets. There are push fit connectors on both the track connections and in addition feed units.

Datacoms systems

Data-communications cabling is a major topic in its own right and is only covered briefly here, but the demand for increased bandwidths and greater network speeds is putting ever more pressure on modern containment systems. These have to protect cables for mains power, as well as delicate high-density hard-wired and optical fibre data-communications cabling in mission-critical structured networks.

It is essential not to skimp on cost, as unsuitable data cable management systems may significantly reduce network performance. For example, overly tight bends may cause data loss – a 50mm minimum bend radius is essential. Often today, such systems are application-specific to ensure that networks are properly installed whilst reducing installation time and cost. Typical products are high capacity two/three-compartment trunking systems, plus deep back boxes and steel dividers (meeting BS50174-2).

And finally…

Cable management is an essential step during the installation of building electrical and data services, tidily securing electrical, data, and other cables. Cable management systems, long essential in the electrical installation sector, are now becoming increasingly important in many other fields, including IT, communications and local area networks (LANs). There are, therefore, many products and services available to electrical contractors and installers that will make their working lives easier and more productive. Cable management evolution has not slowed – quite the reverse.