Put to the Ultimate Test – Part 6: Aging Tests
During the development of our cables and wires, we vigorously test each product in our testing laboratories. In the sixth part of our series, we’ll introduce you to our aging tests.
Cables and wires for industry and infrastructure have an average lifespan of 20 years and need to be able to endure mechanical loads without developing age-related damage such as tears or breakages. To avoid this, organisations such as VDE and UL have defined standards that dictate which types of resistances to aging that cables and wires must demonstrate. Thermal aging, specifically, plays a role, meaning the time span in which a cable remains functional given a certain environmental temperature.
HELUKABEL performs strict aging tests on our products according to these standards. However, waiting 20 years for a result is, of course, not an option. Instead, the insulation and sheath materials that our cables are made out of spend some time in a special aging furnace. This method recreates specific climactic conditions, thus simulating and accelerating the aging process. The duration and temperature are separately defined according to the standard being tested for. Typically, tests run for seven, ten, or fourteen days at temperatures between 100–155°C. Before and after testing, the tensile strength and fracture strain of the plastic are tested. The pre- and post-aging results must be the same. Then and only then can the material pass the aging test.
Since our cables are subjected to a wide range of conditions in a variety of applications, we also test for resistances to different substances in our testing laboratory. In addition to a special hydraulic testing oil called IRM 902, our experts often also receive customer-specific media to test with, and sheath and mantel materials are submerged in these media for many days. Only if the materials are still able to exhibit the required mechanical strength values after this simulated aging, may these materials be used in cable production.
Ask the Expert
Which insulation and sheath materials are especially resistant to aging?
That depends heavily on each individual application. Basically, it can be said that crosslinked materials, which we use in our high-temperature HELUTHERM cables, are the most resistant to aging. Polyurethanes also exhibit a high resistance to aging, while PVC ages relatively poorly. In practice, many other factors also play a role, such as whether the materials are halogen free or flame retardant, or whether the cable is used in a fixed or flexible installation. Age resistance can also be affected by different material mixtures or the use of additives.
What can be done to make a cable more resistant to aging?
Of course, the plastic mixture used has a large impact on resistance to aging, but even the particular manufacturing processes play an important role. Especially when extruding, meaning when the melted sheath or core insulation material is forced through a dye, coating the element beneath, it's important to closely examine all process parameters, selecting appropriate ones that will later allow the cable to exhibit the required durability. If a material fails the aging test, we always try to make procedural improvements. If this doesn't yield the desired results, a fallback material mixture should be used that is better suited for the specific case.
