Structured support

he sheer volume, speed and anticipated accuracy of data transmission across today's communications networks is making unprecedented demands. Not just on the performance of the software and hardware involved but, increasingly, on the entire cable management support system.

"Any chain is only as strong as its weakest link and the effect of a cable system failure in this day and age is likely to result in very expensive network downtime and the possible loss of business and goodwill," observes Alan Conybeare, director of cable management company Kinstrut.

The impending ratification of the Category 6 standard will have wide-ranging implications for the industry. Under this, provision will need to be made for a 20-year lifespan of a system as a whole.

Kinstrut believes that there are ten fundamental principles crucial to the long-term performance of a cable management support system, which must be considered based on the manufacturers' and installers' requirements:

• a flat, smooth-based system gives optimum performance;
  
• basket size should allow for system expansion;
  
• other protective considerations;
  
• minimise water and heat damage;
  
• create pan areas to prevent congestion;
  
• clear labelling helps routing identification;
  
• pathway sharing and bridging must follow guidelines;
  
• use cable ties at frequent centres;
  
• correct working with risers;
  
• earthing and bonding of metallic pathway systems.

As technology brings faster speeds and wider bandwidths, cables installed on irregular surfaces may experience signal deterioration. For optimum performance, it is recommended that cables be laid on a flat, smooth, snag-free, cable support.

Depending on the volume of cable to be installed, an adequate level of protection must be provided on open basket to ensure that there is no deformation of the bottom layer and the cables will not sag between the mesh when the basket is fully loaded. There is no need to use a lining for only one or two layers of cables if the distance between the mesh is not over 50 mm and there is no intention to install more cables at a later date.

Generally, the containment system should be sized so that around 50% is filled during the initial installation. This allows plenty of room for future system expansion without incurring further building work.

Unless protective measures are taken, damage may occur at corners and junctions. Special bends, tees, crossovers and reducers must be designed for total cable protection.

The possibility of cable damage due to water ingress or general dampness is a major problem for cable system designers. To minimise this risk the cables should be raised above floor level by using pedestal supports or integral legs.

Legs are available in different heights to suit specific project needs and mesh cable baskets also provide good ventilation to the installed cables. If water damage does occur, the cables should be removed immediately, wiped with a soft cloth and left to dry. Prompt action should help lessen any long-term damage.

When positioning cable pathways care should be taken that they do not run close to a source of heat.

In particularly congested situations, pan areas can be created to ensure that cables are suitably laid. These areas are formed by manufacturing the support system in very wide sections with built-in sleeves, to allow pedestal legs or supports to pass through. An area as large as 122 m2 has been installed with this configuration at one project in Canary Wharf, London.

Routine maintenance or fault diagnosis can be simplified and made more cost-effective through the clear labelling and documenting of the system. Another ready method of identification is the use of pre-coloured data trays to designate particular cable routes.

When sharing a pathway with electrical services, the guidelines for power separation must be followed. EMI performance is optimised if the power cables are kept to one edge and data cables to the other, with a screened separator provided between each service. If power and data cables are in their own containment system and one needs to cross the other, they should always cross at right angles. A bridge must be used where data cables cross multiple high voltage cables. The base of such bridges should be screened to provide protection against electromagnetic interference.

Cables should be grouped in small bundles of 24. Cable ties should be used at frequent centres along the main cable pathway; centres of between 300 mm and 500 mm are recommended. These ties should not be over-tightened, as they may strangle the cables; this can be avoided by the use of a Velcro-type hook-and-loop tie.

To prevent damage to the cables when working with risers, always lower the cables; do not pull them up the riser.

All metallic pathway systems should be suitably earthed and bonded. Earth tags are recommended for this purpose, these are mechanically screwed to the basket joint coupling system to ensure earth continuity. This in turn must be taken to an independent grounding terminal.

Information on best working practices and the different methods that can be employed for effective earthing of systems are given in EN 50174-2.