Selecting the right finish for steel wire cable tray systems in data centres

Legrand has developed a zinc aluminium finish surface treatment for its Cablofil steel wire cable tray system, suitable for both the white and grey space of data centres.

Legrand Cablofil wire mesh cable tray systems offer data centre professionals a wide range of benefits, including easy installation, maximum cable capacity and improved airflow. The advanced durable and corrosion-resistant design ensures this system can withstand demanding data centre environments, with customisable options that allow users to create a solution that meets the specific needs of each facility.

Independent laboratory testing shows Legrand’s Cablofil products significantly reduce electromagnetic interference when installed and earthed correctly. The surface finish of the steel structure absorbs EMI and keeps disturbance away from the cables, having a minimal impact on connected devices.

Legrand experts believe the main concerns when selecting cable management products to be used within the white space area of a data centre are the potential formation of zinc whiskers or zinc flakes on steel wire cable trays, as well as the importance of a system that will not damage cables once installed.

Although there are various material finishes of steel mesh cable trays currently available to data centre stakeholders, experts believe a zinc aluminium finish is perfectly suited to the demands of modern data centres. In contrast to electrostatic risks, the threat of zinc whiskers is considered negligible.

What are zinc whiskers?

The formation of zinc whiskers on zinc coated products within data centres are a concern for IT system managers.

Zinc whiskers are filaments of pure zinc that grow from steel surfaces and when these zinc whiskers form, they can break off because of scuffing, scraping or vibration. Zinc whiskers can then become airborne and potentially land on sensitive equipment, such as circuit boards and electronic components, causing irrevocable damage.

For industrial environments the appearance of occasional zinc flakes is generally not an issue. However, for clean room environments, like data centres, zinc flakes may not be acceptable.

Legrand’s pre-galvanised zinc aluminium finish (ZnAl)

Legrand’s advanced surface treatment for its Cablofil steel wire cable tray system involves a process similar to that of traditional pre-galvanisation. However, the wire material is immersed in an alloy containing zinc and aluminium. The welding process has also been adapted to prevent ‘weld burns’ or vulnerable points for corrosion, which can occur with traditional pre-galvanised steel wire tray systems.

Legrand’s zinc aluminium finish also offers greater longer-term resistance to corrosion and ensures extended lifetime expectancy compared with conventional hot dip galvanising after manufacture.

Tests on this zinc aluminium surface finish have withstood over 1 000 hours in salt spray trials, resulting in certification as a Class 8 finish product. As such, by specifying the zinc aluminium finish, users have peace of mind that the support system is designed and built to last. To date, zinc whiskers have not been found on any ZnAl coated Cablofil products.

This pre-galvanised zinc aluminium finish enhances Legrand’s Cablofil steel wire cable tray system, which boasts other important features including the T-welded safety edge, a fast assembly system (FAS) and high performing load bearing properties.

Electroplating (EZ)

Cable tray and accessories are generally made from raw steel. These components are then deep cleaned and immersed into an electrolytic bath containing zinc.

The introduction of an electric current through the bath establishes the connection between the steel and zinc, creating the zinc coating. A top coat is usually added in a separate aqueous process that enables the top layer of zinc to become less reactive and increases corrosion resistance.

Zinc-plated products are generally smooth, shiny and clean and have a long ‘shelf life’ in indoor applications, like data centres. Although it is possible that zinc whiskers could form in electro-plated products, this is still the preferred finish for most data centres around the world. In fact, leading electronic equipment manufacturers use zinc-plated chassis and drive cover hardware within their own manufactured products.

Powder coated (PC)

An epoxy powder coating can be applied to steel using an organic, acrylic, chromate or polyester coating. This process is largely used when there is a requirement for the cable management to be a particular colour, in which case specific RAL numbers are provided, to ensure the exact colour is achieved. Painted products do not necessarily eliminate the risk of zinc whiskers. However, this finish can be an aesthetically attractive proposition and is an effective method to identify cable runs.

Pre-galvanised (PG)

Pre-galvanised – also known as hot dip pre-galvanised, or simply ‘pre-galv’ systems – are manufactured with steel that has been galvanised by continuous immersion in a zinc bath prior to the product’s manufacture.

Pre-galvanised steel wire cable trays often show ‘weld burns’ as there is no surface treatment applied after the product is manufactured. The use of pre-galvanised cable management products for data centre applications is highly popular, not only because of price efficiency, but also due to the belief that zinc whiskers will not form on pre-galvanised products.

However, Legrand specialists believe that pre-galvanised finish steel wire cable trays do not offer the same resistance to corrosion as other finishes, such as electrozinc-plated, hot dip galvanised or zinc aluminium finishes. Tests show that pre-galvanised steel wire cable tray systems show impurity and a lack of surface protection, which can cause the weld area to quickly oxidise.

Hot dip galvanising

Untreated cable management products are normally subjected to a rigorous deep clean and then dipped into a bath of molten zinc. Different micron thicknesses can be achieved by altering the process, or by using a steel with a high silicon content, allowing for longer life expectancies.

After being immersed in a molten zinc bath, the coated product is left to cool allowing the zinc coating to solidify. It is not unusual for ‘zinc flakes’ to build up in any openings, such as cable tray perforations, or in the corners of basket trays. When the galvanising is carried out in a quality-controlled environment, most of these zinc flakes are removed manually using steel brushes.

Conclusion

Electrozinc-plated Cablofil has been supplied to the data communications industry for many years and there have been no reported failures to equipment due to zinc whiskers having been found on Legrand’s steel cable tray systems.

Experts are confident in recommending Cablofil zinc plated steel wire cable trays (EZ) for all data centre projects. Cablofil zinc aluminium finish or the painted product offer an effective alternative over traditional pre-galvanised systems and ensure an extended lifetime expectancy.

Legrand’s advanced pre-galvanised zinc aluminium surface treatment for Cablofil steel wire tray systems is gaining popularity globally as a safe and dependable surface treatment for specialist applications. This system is suitable, not only data centres, but also for installations of all sizes – from light duty requirements in small commercial buildings, to heavy duty installations in refineries and heavy industry applications, like shipbuilding.

To find out more about Legrand’s solutions, please contact Legrand +27 11 444 7971 or

Email legrand.south-africa@legrand.co.za