A Better View for Channel 2
Flame retardant, halogen free, non-toxic, durable, drum-windable and abrasion resistant. Load cables used in lighting rigs must display all of these features. Customer ZDF was the first to use the special HELUEVENT cable in a TV production.
Scissor and mast platforms stretch up to the ceiling like enormous wobbly insects. Lighting technicians are adjusting an army of spotlights attached to the rigging system. These lamps will soon be immersing the stage in all manner of light, shapes and colours, to the strict instructions of the lighting engineer, lending a unique magic to the impending live TV show on the TV station ZDF. Only when you take a look above your head do you see what keeps all the spotlights and moving lamps operational, helping them to transform up to several thousand watts into lumen and lux. Heavy power cables running along the crossbeams supply each and every light source, merging at the nodes into a veritable highway of cables, which form bundles as thick as a tree trunk, then drop down 20 m (65 ft.) to connect to the power supply units. Frank Hornung holds one of the very new-looking black cables in his hand and says, “Our light cables need to withstand a lot of stress with all the assembly and dismantling they have to go through, and they also have to comply with a whole range of safety standards.” The salesman from HELUKABEL knows that PVC cables are employed almost exclusively in stage lighting rigs. “They may be easier to wind onto a drum and to lay out, but they are not halogen free and are therefore toxic in the event of a fire. Since other cable types are required in public buildings and for TV productions, many lighting providers are now starting to replace their cables.” “To allow us to tap into this market, we developed a modern load cable for mobile use in event technology applications that fulfils the applicable standards and is also CE-compliant,” says Hornung as he turns the cable to show the printed wording: “HELUEVENT® Multicore Load Cable”.
CUSTOM CABLE EXPERTS FROM WINDSBACH
For such applications, as well as any others that cannot be accommodated by cables from the standard program, HELUKABEL has a custom design department, where eight engineers – including Robert Müller – develop custom cables at the company’s manufacturing facility in Windsbach. “The specifications with which we were confronted were extremely demanding.” Apart from being flame proof and halogen free, the cable had to be abrasion proof and have the ability to be wound around a drum repeatedly, as well as having a long service life. “Normally, halogen free cables have their own integral flame blocker. However, this tends to make the cable very stiff and brittle, which limits its practical use to fixed applications. A halogen-free cable therefore does not tend to be very flexible. There are only very few plastics on the market that have the right characteristics. At the same time, long service life and good flexibility also contradict each other from an engineering point of view,” explains the design engineer. The search for the right material compositions and structure for the core stranding was like walking a tightrope between normative requirements and the need for flexibility and long service life.
SUPPORT BRAID FOR DURABILITY
Step by step, the cable professionals neared their goal. First, the engineers identified a high-performance TPU that is certified for all safety standards and allowed them to achieve the desired mechanical characteristics. To optimise the cable’s durability, they integrated a support braid into the cable as a means of strain relief. This means that the sheath is divided into two sections by a polyester thread. “This construction is durable, because the tensile forces no longer transfer as much to the plug retainers, because the sheath no longer stretches. Additionally, it can no longer pull out, even if the heavy cable is hanging loosely from the ceiling,” explains Müller. Sales expert Frank Hornung has meanwhile unwound a few metres of the new Multicore Load Cable and looped it around one of the thin steel posts and states, “Our cable designers had to dig deep into their box of tools to find a way of achieving the necessary minimum bending radius of around 13 cm (5 in) for the cable’s day to day use on the crossbeams. They selected a thermoplastic urethane for the strand insulation, which is almost as soft as silicon. The support braid also gives the cable a lot of torsional rigidity to make sure the core strands don’t break.”
ROBUST YET FLEXIBLE
In Hornung’s opinion, a cable’s service life is also important. “When you look around here, you see the conditions in which the cables are required to perform,” he says, pointing to two technicians who are stretching the cable over the edge of a beam for almost its entire length. “The sheath must not wear out easily. Our high-performance material is able to withstand at least as much as standard polyurethane – as evidenced by our abrasion tests.” Based on the approvals and cable performance ZDF recently started using the HELUEVENT® Multicore Load Cable to wire their stages. While Hornung winds the brand-new cable back up into equal loops, he says: “Even though we don’t quite reach the flexibility and low-weight of PVC cables, our product features a considerably longer service life and satisfies all the required safety standards. With our certificates, event organisers and lighting providers are on the safe side if the liability insurance people or fire service come around to check up.”