When a wiring harness requires EMI hardening, the most economical and least labor-intensive solution is to apply Zippertubing’s Zip-On® EMI hardened jacket. However, there are application situations where no tubular shielding product makes sense from an installation perspective.
Below is a classic example of this kind of situation and the highly effective solution that solved it.
An aircraft manufacture had thirty 1950’s era aircraft to upgrade and EMI harden for a special military project. Because these aircraft were simply being retro-fitted and all existing hardware had to be used, the problem arose as to how best shield the prefabricated wire harnesses from EMI. The wire harnesses were fully assembled (connectorized) and had very short runs with numerous breakout branches. The short run lengths, connector encumbrance and high number of breakouts eliminated the use of any available wrap-around or pull-through products. The only solution that made sense was a tape wrap. Tape should always be the last option to be considered since it is a very labor intensive installation effort and adds a lot more material per foot than a tubular product does. Classic knitted wire mesh tape was considered but rejected because it was thick, which would add a lot of volume and require all new clamp sizing. Plus the mesh also could not meet the high frequency attenuation requirements. Foil tape was much thinner but created sharp edges and kinks which risked cutting the primary wire insulation as well as making the overall assemblies far too stiff for aircraft use.
In addition, once installed the EMI shielded cables would require a secondary outer insulation wrap to protect the shielding. This secondary jacketing operation essentially doubled the labor effort and risk damaging the shield layer and potentially creating shield openings in the EMI tape wrap due to the excessive amount of cable handling required to apply the insulation layer.
The customer contacted The Zippertubing® Company’s engineering team and requested an evaluation and solution proposal. At the time, Zippertubing® had no product solution that adequately solved this kind of problem, but it did have the materials and the “out of the box” thinking that was needed to reconfigure them into a form that could meet all the design criteria.
Zippertubing’s ZT-Shield® (3250) was the solution.
Zippertubing® laminated it’s soft, lightweight and highly flexible Z-3250-CN EMI shielding fabric with a thin layer of electrically conductive transfer adhesive tape on one side and then added its high dielectric Polyurethane electrical insulation tape in a unique stagger lamination design to the opposite side. The result was a thin EMI shielding tape that was only 0.013” thick, flexible, with no sharp edges and provided shielding attenuation levels of 85+ dB. When the tape was helically wrapped around the wires harness it created a fully EMI hardened and electrically insulated protective outer jacket all in a one-step installation process.
ZT-Shield® was the answer for minimizing the customer’s installation problem and meeting all of the cable harness shield performance, weight, volume and clamp sizing concerns. Subsequent laboratory and field testing proved that this product outperformed all the customer’s design criteria.
So, the next time you have to solve the impossible, call Zippertubing®; we’re here to assist you.