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Why do we use cable cleats?

Cleats are an often under estimated component of cable management systems, principle they exist to fix, retain and support cables. In addition, where short-circuit faults are anticipated, correct cleating will result in the containment of the cables during a fault and enable the circuit to continue operation with the minimum disruption.

What type of cleat do I need to use?

We currently offer over 25 different types of cleats to suit various installation requirements. These range from our single and two bolt LSF cleats, through to Emperor stainless steel cleats, designed for installation within extremely harsh environments throughout the world, e.g. off-shore petrochemical plants.

In the UK, the majority of commercial and industrial contracts call for the use of LSF cleats, aluminium two-part single way and trefoil cleats, along with the increasing use of stainless steel cleats, particularly since the advent of Fire Performance cables for critical circuits.

The following questions need to be answered to ascertain the relevant cleat for any given installation:

– What is the conductor size?
– What type of cable? i.e. single core, multi-core, XLPE, unarmoured, steel wire armoured, aluminium wire armoured etc.
– What is the overall diameter of the cable?
– Does the specification call for a specific type of cleat or type of material?
– Does the specification call for any fault current requirements?

Common issues and questions raised when ordering cleats:

– Preference for using cables ties to save money, instead of cleats.
– Spacing requirements, i.e. ladder-rack not being wide enough to accommodate the required number of cleats.
– The short-circuit withstand required from a cleat when installing single core AWA cables.
– Suitability of cleat to a particular cable, e.g. Fire Performance cleats to suit FP400 cables.
– Other spacing issues, such as the recommended mounting distance between cleats when installing cables vertically being different from when the same cable is being installed horizontally.

ETS Cable Components are the UK’s leading stockists and distributors of cable cleats and cable management accessories. For more information on our range of cleats, visit our cable cleats page or contact our Sales Team.

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The safe and correct working of accessories used for cable terminations is dependent upon many issues from the correct specification of the product through to competent installation. The following is a list of (maybe obvious) do’s and don’ts which should be adhered to.

The “Do’s” of Cable Terminations

– Do ensure the correct products are specified – such as ColdShrink, Heatshrink or Screened Connectors.
– Do check associated products are compatible and safe to be used together.
– Do check the accessories and cable dimensions match.
– Do ask the manufacturer or distributor for more information on the product is required.
– Do prepare the cable and accessories in a suitable environment (clean and dry).
– Do ensure all staff are trained and competent to carry out the termination.
– Do use the correct tools for the job.
– Do ensure these tools are properly maintained and functioning properly.
– Do make sure the cable lugs/terminals are installed correctly – for crimp connectors, ensure the correct die sets and compatible tooling.
– Do smooth any sharp edges on lugs caused by crimping dies.
– Do read and follow installation instructions carefully.
– Do not forget to install the earthing system correctly.
– Do ensure heat shrink and cold shrink components are correctly positioned before shrinking or removal of cores.
– Do fully test the terminations after installation.

The “Don’ts” of Cable Terminations

– Don’t rush any part of the job.
– Don’t cut corners or take short cuts.
– Don’t allow sheds on adjacent cores of a three-core termination to touch – This can lead to discharging.
– Don’t allow any secondary wiring to be damaged when installing heat shrink sleeving.

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Single-core power cables can be run in a number of formations, the most common include flat or trefoil formations. Each cable formation has its benefits and drawbacks, we’re going to look at the differences between each way for laying these cables.

Trefoil Phase Formation

One of the main reasons trefoil formations are used is that it places the phases the same distance apart, so the magnetic field and circulating currents are equivalent for each cable phase. Typically, trefoil phase formation is more commonly used for Low and Medium Voltage applications up to 132kV due to ease of installation and the reduction in space the formation has across the containment system used. However, installing single-core cables in trefoil formation can mean that the touching cables will exhibit worse heat-dissipation when compared to flat formation, therefore lowering the current-carrying capacity. Considerations which should be taken into account by specifying electrical engineers when designing such systems.

Flat Phase Formation

Rarely used at voltages below 275kV due to the mounting centres having to allow for sufficient heat-dissipation. Running in flat formation, the central phase of the three-phase set is adversely affected by the magnetic fields around the neighbouring phases, leading to a higher running temperature on the middle phase and subsequent voltage imbalance. Phase transposition can be used to counter-act these affects, but the necessary mounting space required for such installations usually precludes their use in most industrial/commercial installations and flat formation tends to only be used by major DNOs in their distribution networks.

Trefoil formations are chosen for applications where space is at a premium and flat formations also tend to be less cost effective due to the increase potential cable route space they take up. Our experience of such installations has generally been with cables above 132kV, with cables under 132kV being laid in a trefoil formation.

Triplex Formation

An adaptation of the trefoil formation can be found with the increasingly popular Triplex formation. Triplex cables are three conventional single-core cables supplied pre-wound in trefoil formation by the cable manufacturer/vendor, the three cores having been slowly twisted together during the manufacturing process and supplied on one drum, offering significant benefits in installation time.

Due to the constant phase rotation of the cores, using conventional trefoil cleats is not possible as the position of the mounting base will not be constant. For this reason our Triplex Cable Former provides a cleating solution, allowing traditional trefoil cleats to be used. Learn more about our offer of power cable lugs.

Cable cleats suitable for each cable formation:

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