Claims have recently begun to emerge from certain quarters that imply stainless steel cable ties can be placed on an equal footing with cable cleats.
Amongst the claims being made are:
- “Metal ties actually provide as much protection in the event of a short circuit as cleats.”
- “Stainless steel cable ties are less expensive on average than cable cleats.”
- “Stainless steel cable ties provide an equal or better level of risk mitigation at lower cost and quicker time to install.”
My problem with these assertions is that although stainless steel cable ties and cable cleats are complementary products, the area of overlap is extremely small – and when explored fully, it’s immediately apparent that it’s an area of considerable risk. What this means is that the kind of claims being made about stainless steel cable ties are, at best, extremely misleading.
Product v product
Cable cleats are made in a variety of materials to accommodate a wide range of installation conditions and locations. Our product range alone features stainless steel, mild steel, extruded aluminium, cast aluminium and a wide range of polymers. Many of our cleats combine metals and polymers to deliver the best solution.
Cable cleats also come in a number of different varieties. Again using our product range as an example, we supply cable saddles, cable straps, flexible cable cleats, hinged cable cleats and even the most straightforward of cable clamps.
In contrast, a stainless steel cable tie is just that – a cable tie available solely in stainless steel.
Creating an analogy about the two products highlights the scale of the differences between them perfectly: A stainless steel cable tie manufacturer may claim their wrench is as good, if not better, than the cable cleat manufacturer’s. But the cable cleat manufacturer retorts by pointing out they don’t just have one wrench, they have an entire tool kit.
Before even considering the question of price, we first have to decide which of the many types of cable cleat we should compare the stainless steel cable tie with.
In the examples I’ve seen, the price comparisons between the two tend to pit cable cleats at the upper end of their range against cable ties. While this may seem unfair, the comparison has been made so let’s see how it stands up to scrutiny.
First, it’s obvious that a single stainless steel cable tie will be cheaper than what is the strongest of stainless steel cable cleats – after all, you get what you pay for. But even so, would the entire cost of both product and installation be cheaper if you used cable ties rather than cleats? It may surprise you to discover that the answer is almost certainly no – but why?
When considering the strongest stainless steel cable cleat it is ludicrous to try and equate it to a single stainless steel cable tie. Yes, both products are made from similar material, but there is, of course, a lot more steel in a cleat than a tie. Therefore, in order to make a direct comparison you need to consider the cross sectional area of the material being used – a calculation based on width, thickness and the number of times it is wrapped round the cables.
Cable ties are typically less than 20mm wide and less than 0.4mm thick and so have a cross sectional area of less than 8mm2. If the strap is wrapped round twice we have material with a maximum cross sectional area of 16mm2 securing the cables. In comparison, a top of the range stainless steel cleat will have a cross sectional area of 100mm2.
Harking back to simple physics, the ultimate tensile strength of a material is proportional to its cross sectional area – and that’s something you simply can’t argue with.
Using the information above, and all relevant supporting short circuit test data, if the calculated fault level for a system required the installation of an Ellis Emperor cleat every 300mm, it would come as a great surprise if the cost of the equivalent appropriate number of cable ties was less than the cost of the cleats – and that’s before you even take into account the time it would take to install them all.
The final point I’d like to address is short-circuit testing, and in particular the question of whether the data gathered from a test is transferable to a real life installation?
As far as cable cleats are concerned, the answer is usually yes. This is because, under fault conditions, a cable cleat constrains all the forces generated between the cables. The mounting structure has no influence on the cleats performance and so it should perform at the level indicated on the short-circuit test certificate.
The situation is nowhere near as cut and dried when it comes to stainless steel cable ties – mainly because of the difference in fixing methods. Typically there are three ways in which a cable tie is used to attach cable to ladder:
- The cable tie can be wrapped around both the cable and the rung.
- The cable tie can be installed using a mounting bracket, which fixes to the rung.
- The cable tie can be fed through perforations on the ladder rung if they are present.
Of these three methods, both option 1 and option 3 introduce significant variables that will have an impact on likely performance during a fault. In both cases a foreign body is being introduced to the loop that contains the cable. As such everything from ladder material to rung profile; types of hole and sharpness of edges; and even surface finish and cable diameter can have an impact on the whole arrangement. As such, it’s impossible to say that the result of a short-circuit test on a stainless steel cable tie is transferrable to the real world, unless the installation is identical to the testing set-up.
Of course, installation option 2 is more likely to deliver real-life performance that matches short-circuit testing performance for a cable tie. But in this scenario both the cost of the parts required, and the installation time will increase significantly, making it even less competitive when the number of ties to cleats ratio is taken into account.
The final decision
What needs to remembered when considering the respective merits of both stainless steel cable cleats and cable ties is that the primary concern for all those involved in electrical cable installations should be safety.
In order for an electrical installation to be deemed safe, cables need to be restrained in a manner that can withstand the forces they generate, including those generated during a short-circuit.
Yes, both cable ties and cable cleats have their place in the specification picture. And yes, there is a minimal amount of overlap where it is feasible that an installer or specifier could choose one over the other. But it is minimal, and the specification decision shouldn’t be made based on misleading claims aimed squarely at undermining the sales of a tried, tested and trusted solution.
All cable cleats designed and manufactured by Ellis Patents undergo a thorough testing program prior to launch, including short-circuit testing. Even after launch, products are regularly short-circuit tested and will perform at the level on the relevant certification during a real life short-circuit scenario. Not one of our installed cable cleats has ever failed. Therefore, make sure you make the correct specification decision on your next electrical installation. If you don’t the dangers posed by a short-circuit are plentiful – costly damage to cables and cable management systems, plus the risk to life posed by incorrectly installed live cables.”
For more on Ellis, its products and services visit www.ellispatents.co.uk, call +44(0)1944 758395 or follow them on Twitter @ellispatents.