• • • CABLING & CABLE MANAGEMENT • • •
Stay secure: The essentials of specifying cable cleats
Kelly Brown, sales director, Ellis Patents, says the importance of making the right decision when specifying cable cleats and the steps that need to be taken to ensure they are correctly specified
T
he knowledge that cable cleats are a crucial component in electrical installations is well understood in recent times, and with that awareness has come an increase in the number of products available,
This can only be a positive thing, but it also can make the decision on which products to choose harder. Ellis Patents has been advocating the importance of correctly specified cable cleats for many years, and today there are an increasing number of manufacturers delivering the same message. While competition is healthy for driving product development, customers are now faced with numerous products that look remarkably similar, and in some cases, products are marketed
that a cable cleat is suitable for specification and installation. Additionally, cleat spacing is another critical factor that buyers need to consider when specifying cable cleats. The system’s peak fault current and cable phase spacing must be known to calculate the forces between two conductors during a three-phase fault. The formula in FIG 1, as detailed in the International Standard (EIC 61914), demonstrates the correct way to calculate the force value.
as computer renderings before they have even been produced.
This makes it challenging for customers to differentiate and distinguish fact from fiction during the specification process. Therefore, when specifying a safety-critical product like a cable cleat, buyers must rely on confidence and trust when making their final decision.
Buyers need to consider the company behind the product and their technical expertise. It’s essential to
understand if the manufacturer has the depth of
knowledge and experience to help if things go wrong and if the product has been
proven to work in similar
circumstances. Secondly, mechanical strength and short-circuit testing are critical factors to
consider when specifying cable cleats. Cable cleats need to be able to withstand specific fault conditions, and mechanical tensile testing alone can be misleading as it is slow and controlled. In
contrast, short-circuit testing is the only reliable method of proving
28 ELECTRICAL ENGINEERING • JUNE 2023
Once the force value is determined, the optimum cleat spacing can be calculated. It’s crucial to understand that, regardless of the short- circuit level, a system must use a fault-rated retention device. It’s also recommended to use a maximum spacing of 300mm when installing systems on bends and risers. Finally, buyers must consider the risk of material corrosion in the installation environment. Galvanic corrosion occurs when dissimilar metals come into contact with each other in the presence of an electrolyte, and it’s not easily predictable. Separating dissimilar metals with polymer separation washers is the safest course of action to prevent galvanic corrosion. The corrosion resistance properties of stainless steel make it the material of choice for cable cleats and fixings, with 304L and 316L being the most commonly used variants.
The corrosion resistance properties of stainless steel are a result of chromium, which reacts with oxygen and forms a self-healing impervious layer of chromium oxide on the surface of the steel. In most circumstances, this layer is extremely durable, but in certain locations, such as railway tunnels, the oxide layer can be penetrated as a result of mild steel dust in the atmosphere, which reacts with moisture to exaggerate corrosion. In such circumstances, aluminium products or electrostatic plastic coatings should be used. Contracts often require a guarantee of the cable cleat’s life expectancy, and it becomes complicated if the cleat or its fixings are manufactured from galvanized mild steel. The thickness shown on the Galvanizers Association map should be referred to in such situations, which highlights corrosion rates across the UK, and a calculation made regarding the necessary thickness to ensure the cleat’s durability. In conclusion, when specifying cable cleats, buyers need to consider the company behind the product, the mechanical strength, and short-circuit testing, cleat spacing, and the risk of material corrosion. By following these steps, buyers can make the right decision when selecting cable cleats, ensuring safety and optimal performance in electrical installations.
electricalengineeringmagazine.co.uk
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