A true servo cable all-rounder

The North American market is complicated – particularly when it comes to standards. In order to avoid any unpleasant surprises, machine manufacturers should rely on components that are approved or listed there – such as the ÖLFLEX SERVO FD 7TCE from LAPP.

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The ÖLFLEX SERVO FD 7TCE meets all important standards in both Europe and the USA. It is suitable for both static installation and mobile use in cable chains with moderate to high travel paths and acceleration.

 

 

It is not uncommon for technicians from a German machine manufacturer to be in a production hall in the USA and want to cable a new machine and put it into operation. Then the county sheriff comes along and says: "No". After a long discussion, it becomes clear that the cables used are approved in Europe but don't have the approval or the listing that matters to the local sheriff. There is then a frantic search for suitable cables that are actually approved; they may not be as good technically, but the main thing is that the sheriff is happy as they have wide discretion to give you a nasty surprise.

 

You can avoid these types of situations if you use cables that meet all US standards and are top quality technically right from the outset. It is hard to achieve this balancing act. The ÖLFLEX SERVO FD 7TCE has achieved this in a number of ways – a new cable from the Core Line Performance class from LAPP. It meets all important standards in both Europe and the USA and is suitable for both static installation and mobile use in cable chains with moderate to high travel paths and acceleration; it is also flame and oil resistant – making it a true all-rounder amongst cables.

 

UL & CSA – the measure of all things

Particularly the first issue – meeting various application standards – causes headaches for machine manufacturers that export to the USA and Canada if cables are not listed according to UL or CSA (Underwriters Laboratory / Canadian Standards Association). One alternative are AWM-style (appliance wiring material) cables according to UL 758 – a standard that allows greater freedom. However, these cables cannot be installed at the customer's premises on US soil or routed on cable trays, for example; this may have to be carried out at the machine manufacturer's site in Europe, for instance – which is not an option for larger systems.

 

Those who are familiar with the maze of standards are able to find a solution for any challenge. However, that is time consuming because the matter is complex. Take the example of cable insulation: many high-quality cables in Europe are wrapped with notch and oil-resistant polyurethane and, in technical terms, this would also fulfil US demands. If only standardisation didn't throw a spanner in the works. In particular, it doesn't consider PUR at all suitable for use for UL or CSA-listed cables. For cable manufacturers such as LAPP, this means that developers have to find a way round this in terms of material technology. Thanks to a special mixture of a thermoplastic elastomer, the ÖLFLEX SERVO FD 7TCE fulfils common guidelines and standards for listed cable products.

 

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Chancing your luck when it comes to the material

The developers from LAPP also had to think of something new when it came to the insulation of cores. Listed cables for routing on cable trays or use in industrial machinery in the USA often have insulation made from PVC which is covered with a thin layer of nylon in order to increased oil resistance. PVC is self-extinguishing in the event of fire, but forms caustic vapours due to its high chlorine content and also forms corrosive hydrochloric acid in combination with extinguishing water. In addition, PVC is not exactly one of the materials with the best insulation characteristics. The poorer electrical characteristics mean that these types of cables cannot bridge excessively large distances without any losses. This means that in larger systems in the USA, it is sometimes necessary to reconnect PVC-nylon-insulated cables that come from the cable tray to a lower-capacity AWM cable with corresponding core insulation as they continue on to the drive, for example via an energy chain – although it is actually not approved for on-site cabling.

 

In the case of cables with insulation made from polypropylene (PP), as is common in Europe, routing from the control cabinet to the drive is simpler. PP has significantly improved electrical characteristics and therefore allows the bridging of larger distances due to its low capacity values. However, US standardisation also throws a spanner in the works here – according to North American regulations, PP is not necessarily intended as a listed core material for routing in open cable ducts. Similarly, it also often sets limits when it comes to standards with respect to the use of polypropylene for the MTW listing (machine tool wire) required for the cabling of industrial machines. LAPP USA therefore uses a special material made from XLPE that provides insulation for ÖLFLEX SERVO 7TCE, which can be routed in a fixed manner. In the new version suitable for drag chains with extra-fine conductors, the ÖLFLEX SERVO FD 7TCE, the insulation consists of cross-linked ethylene propylene (EPR) for increased flexibility. Both plastics are listed according to US regulations and allow cable lengths that are up to 40 per cent higher than those of US cables with conventional PVC-nylon insulation. This means that the choice of core material is by no means a poor compromise, but rather, as we are used to from cables for the European market, guarantees top electrical characteristics for the North American market, despite the prevailing complex standard requirements there. There is also change in the air at companies in the USA when it comes to the issue of sheath material: a large American car manufacturer and customer of LAPP in the USA is not using PVC-wrapped cables in its factories, but instead prefers the TPE special mixture used by LAPP as an outer sheath material.

The sheriff decides

"It's not just the US standards that are complicated, but also their application," states Frank Hörtnagl, Product Manager for ÖLFLEX SERVO at LAPP. It is the responsibility of the respective states to transpose new standards into applicable law. This applies, for example, to the relevant technical standards for the cabling of industrial machinery in the USA, the 2012 and 2015 editions of the NFPA 79 (National Fire Protection Association). They closely interact with the National Electric Code (NEC); the most important set of rules for exporting machine and plant construction firms.

 

The states have a certain amount of freedom in how they implement them, for example when it comes to timing. It may therefore be the case that some states rely on older versions of the NEC that, in turn, refer to older NFPA editions. Moreover, each state can declare further specific requirements and guidelines to be mandatory. For example, in San Francisco in California there are significantly higher fire protection requirements in place than in other cities even within the state of California due to devastating fires after the 1906 earthquake.

Developed with US expertise

The ÖLFLEX SERVO FD 7TCE gives users the security they need. They were developed at LAPP in New Jersey and are also produced there. The experts there have many years of experience with US standards; some of them have even worked for UL authorities. The cable isn't cheap, because production is more complex, in particular due to the cross-linking of the core plastic. Nevertheless, these types of universal cables from LAPP's range are enjoying increasing popularity because, all in all, they don't just save the user money because routing is simpler and they only need to have one type in stock rather than various types of cables, but they also save time and hassle when it comes to standards, as their broad variety of recognised UL & CSA listings cover a wide range of uses. This allows the customer to use cables without any problems or having to worry about the long arm of the law – in this case, the above-mentioned sheriff.

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Frank Hörtnagl, Product Manager for ÖLFLEX SERVO at LAPP