ELLIS news items

Inappropriate Cleats put Installations and Lives at Risk Warns Ellis Patents

ellis cable cleatLeading cable cleat manufacturer, Ellis recently issued a stark warning that incorrect interpretation of short-circuit test reports was leading to inappropriate cleats being inadvertently specified and installed. According to the company’s MD Richard Shaw, this situation is putting vital electrical installations and lives at unnecessary risk.

“The role of the cable cleat in any electrical cable installation is of paramount importance in terms of safety and system integrity. They are there to prevent costly and dangerous damage to cables and those around them in short circuit situations – in fact, and as I’ve often said before, the only thing underspecified cleats do in a short circuit situation is add to the shrapnel.

Historically, this message, no matter how hard-hitting, has never been fully appreciated and so rather than being treated as an integral part of an electrical installation, cleats have often been lumped in with electrical sundries and seen as fair game for cost-cutting.

This mindset has slowly been changed over the years, including the introduction of regulations governing the use of cleats (EN50368 / IEC61914), but there is still a long way to go before the finishing line even comes into sight.

Ironically, one of the issues currently clouding the picture is something I have long championed as a tool for resolving the problem. That is, the use of third party short circuit testing to prove a cleats’ suitability for a particular installation.

Testing times
Third party short-circuit testing is the only way to effectively prove a cleat does what it claims to and is something we carry out as standard on any new product. In the past, I would have said the widespread adoption of our approach would have cleared the cleat picture up once and for all. But today, it seems that isn’t enough to resolve things.

Firstly, there’s the fact that when looked at closely some cleats simply aren’t what they claim to be. Sometimes this can be down to issues surrounding manufacture, but more often than not it’s short-circuit withstand claims that simply don’t stand-up to scrutiny, which means the cleats are likely to be wholly unsuitable for installations they claim to be designed for.

And then there are the issues generated by the reports of properly tested products. Short circuit reports in general tend to be lengthy, in-depth documents and so a lot of people will be tempted to quickly refer to the headline figure rather than properly reviewing the entire document.

The danger with this is that some will take it to mean that the products tested deliver the same level of short-circuit withstand irrespective of the installation. For example, the headline figure may say a specific cable cleat has a short circuit withstand of 150kA, but this needs to be backed up with a qualifying statement that puts it into context – something say along the lines that the cleat has a short-circuit withstand of 150kA when securing 43mm cable in trefoil at 300mm centres.”

Shaw highlights a recent report he was given that showed a product withstanding a peak short-circuit of 138kA, but that on full reading it became clear that the test rig was set up with four trefoil circuits in parallel and that, under these circumstances, although the overall fault level was 138kA, each of the four trefoil groups only saw a quarter of the fault, equivalent to 34.5kA.

“Worryingly, the example is just one of many and the moral of this story is clear – don’t judge a short circuit test report by its cover,” he continued.

The story clearly highlights the need for third party test reports to be carefully analysed prior to being acted upon. Of course, this puts the onus on the specifier or contractor to do this work, but as a leading manufacturer we feel we should play a far more active role in ensuring correct specification of our products.

Interpretation
In order to correctly interpret a report those with specification responsibility should ask two simple questions. Firstly, is the product tested the same as the product being offered? And secondly, is the test installation similar to the project installation? For example, a test of three single conductor cables in parallel secured with single cable cleats cannot be compared with a trefoil installation secured with trefoil cleats.

This can all then be backed up by calculating the forces experienced by the cleat during the test and comparing it with the anticipated force the nominated cleat would see in the proposed installation.

Admittedly, this sounds very complex and many will breathe a sigh of relief when they hear there is an easier way round it.

Be specific
Project specific testing removes the opportunity for any misunderstanding by testing a particular product to ensure it can stand up to the requirements of a specific project.

This is third party testing at its most extreme, and at present it’s the only way to deliver an absolute guarantee that the cleat being installed is suitable for the installation.

It does though need to be noted that the certificate this delivers is specific to the installation its fault level, spacing and cable configuration. A cleat’s short circuit withstand, which is seen as the indicator of its suitability for a project, is only valid for a cable diameter equal to or greater than the diameter of the cable used in the test. So if the project in question ends up using smaller cables than those referred to in the test then the force between the cables is proportionally greater, meaning the certificate is inappropriate and the cleats will not provide the protection they are installed to give.

This could then be supported by the adoption of cable cleats as short circuit protection devices, which would automatically give them the same degree of importance as fuses or circuit breakers.

The argument for this isn’t as outlandish as it first sounds. In the event of a fault, the forces between cables reach their peak in the first quarter cycle, which is the point that cleats earn their crust. In contrast, circuit breakers typically interrupt the fault after 3 or even 5 cycles by which time, if the cleats are underspecified, the cables will be long gone.

It does seem that the process of overhauling perceptions of and attitudes towards cable cleats is far more difficult than it should be. On the one hand it seems to be being hindered by those who seem intent on making sales through the exploitation of the lack of widespread knowledge about cleats and short-circuit tests. While on the other, there still seems to be a strong undercurrent of those who are averse to allocating a suitable budget allocation to cleats – despite the fact they save lifetime cost and deliver safety and peace of mind.

In a perfect world, the widespread adoption of project specific testing and the adoption of cleats as circuit protection devices would resolve every issue. And while I am hopeful this will eventually happen, I’m realistic to know if won’t occur overnight – until then myself and everyone else connected with Ellis will continue to bang the drum for cable cleats wherever and whenever we are given the opportunity and slowly the tide will continue to turn.”

Ellis Patents prides itself on the extensive third party testing it puts all of its products through prior to taking them to market and the fact that they will always agree to project specific testing to secure an order.

Ellis Patents

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