All electrical industrial cable protection systems and conduits are not created equal. For decades, PVC-jacketed metallic conduits (otherwise known as liquidtight) have dominated most industries in the US market as a standard for cable protection applications, even though emerging technologies far outperform them in many aspects.
Conversely, the European market has not used PVC-jacketed metallic conduits since the 1980s. Almost every industry in Europe has taken advantage of the latest in cable protection technology, a variety of highly engineered and specially modified polyamide systems. The most compelling advantages for the use of these highly engineered polyamide conduits and fittings are the drastically reduced assembly times, high impact resistance, and flexibility associated with the products.
In a recent study done by an engineering manager at a US-based manufacturer, it was determined that the assembly of polyamide conduits will reduce assembly times to one-fifth the time is takes to assemble PVC-jacketed metallic conduits. The cost reductions associated with this type of labor savings speak for themselves.
In addition, the study determined that polyamide conduits are more impact-resistant than PVC-jacketed metallic conduits by running a forklift over both engineered polyamide PA6 conduit and PVC- jacketed metallic conduit.
Although polyamide cable protection technology is the standard in conduits and fittings within the worldwide rail, transit, hybrid vehicle, and wind industries, it is still not as widely known as the heavily standardized PVC-jacketed metallic conduits and fittings. The reason is polyamide cable protection systems are relatively new to the North American market and the majority of electrical and mechanical engineers throughout the United States and Canada are not educated in the technical advantages of the technology.
Polyamide conduits and fittings take one-fifth the time to assemble as compared to PVC-jacketed metallic conduits. The cutting procedures for PVC-jacketed metallic conduits require either a hack saw or ban saw, which take one to two minutes per cut and leave sharp jagged edges that must be de-burred. Polyamide conduits, on the other hand, are literally cut to length in seconds with a simple cutting tool and produce no sharp edges that require de-burring to prevent cut hands or conductors. Polyamide connectors are terminated within seconds and, depending on the manufacturer, require no tooling of any kind to make the connection. PVC-jacketed metallic connectors take approximately two to three minutes per connector to properly terminate. In the case of highly engineered polyamide cable protection systems, a higher quality product costs much less in the long run.
Multiple Recipes, Multiple Applications
Polyamide is a very high-performance polymer, derivative of nylon, for which there are numerous recipes for a variety of applications. A few examples of the superior performance characteristics of polyamide cable protection follow:
One of the most common misconceptions about polyamide cable protection technology is that a specialized nylon derivative cannot be as impact-resistant as metallic conduits. Performance studies have shown, however, that highly engineered and modified PA6 polyamide, commonly available with impact-resistant additives, far outperforms any metallic conduits available on the worldwide market in terms of impact and crush resistance. Take a hammer to a PA6 high-impact polyamide conduit on a cement shop floor and be prepared for the hammer to bounce back with significant force with no damage done to the conduit or the internal conductors. Using the same hammer test with the most commonly specified PVC-jacketed metallic conduit results in crushed conduit, crushed internal conductors, and system failure.
One of the most basic concepts behind the development of polyamide cable protection technology is that of extreme flexibility. The majority of all robotic dress-pack manufacturers prefer the use of polyamide conduits and fittings, due to its ratings of up to several million reversed bending cycles. All polyamide conduits are much more flexible than PVC-jacketed metallic or the most basic metallic conduits (if you over-flex PVC-jacketed metallic systems, the internal metal core will come apart and tear through the PVC jacketing, rendering the conduit useless). This extreme flexibility makes polyamide cable protection much more convenient where space, aesthetics, bend radii, and motion are essential to the application. In addition, polyamide conduits remain flexible, regardless of extreme temperature variances and time in the field.
Corrosion Resistance/Ingress Protection
Another of the core concepts behind the development and implementation of polyamide cable protection systems is that of longevity and mechanical integrity in environmentally challenging applications. PA6 and PA12 polyamide conduits have proven to remain corrosion-proof for more than 40 years in outdoor applications. By comparison, PVC-jacketed metallic conduits will eventually rust, corrode, and fail within a few years in the field. PVC-jacketed conduits also attract rodents, which chew through the PVC jacketing and cause system failures when they mark their territories. Due to the molecular structure of polyamide systems, and the lack of desire by rodents to chew on the polyamide material, this is a non-issue with the highly engineered polyamide system.
Considering the fact that fuel costs have increased significantly worldwide, especially in Europe, an additional consideration for choosing polyamide cable protection technology is the product’s lighter weight. Polyamide cable protection systems are used almost exclusively in the worldwide rail and transit industry because of the comparatively lighter weight of the polyamide conduits and fittings versus PVC-jacketed metallic conduits. Considering the significant amount of cable protection necessary in commuter and light rail cars, polyamide cable protection’s weight has a considerable impact on fuel savings in rail, transit, hybrid truck, bus, and commercial vehicle operations.
The chemical resistance of polyamide mixtures make them a good choice for a very broad spectrum of applications. From standard polyamide 6 and 12, to polypropylene (PP) with highly caustic chemical resistance properties, to polyurethane (PU) with good abrasion and microbe resistance properties, there is a polyamide product available to meet the challenges of all harsh chemical environments.
Polyamide conduits and fittings were quickly adopted in the European and North American solar industries due to their exceptionally high degree of UV protection. One of the largest solar farms in the world, located in Saudi Arabia, utilized polyamide exclusively in the construction of the project, and there is a growing awareness among North America’s solar installers of the advanced UV-resistant characteristics of the polyamide cable protection system. PVC-jacketed metallic conduits, by comparison, will not withstand prolonged exposure to the sun and will crack, corrode, rust, and fail under even the most ideal environmental conditions.
One product that is a mainstay in the rail transportation industry is the specially engineered PA6, with its low smoke and low toxicity characteristics. This flame resistance meets several ASTM and SMP specifications for flammability, smoke emission, and smoke toxicity. There are also several products with unique characteristics, such as shielding against EMI/RFI interference; high-temperature conduits for use in applications rated up to 350°C continuous; and oversized jumbo conduits up to four inches in diameter.
Know Your Options
There is a polyamide product for every possible cable protection application. When comparing the relatively new polyamide conduit technology to the more dated, more known PVC-jacketed metallic conduits, polyamide has very few limitations. Not only will mechanical and manufacturing engineers save significant time and cost in the assembly and termination of polyamide cable protection systems, the product is more rugged than steel, more environmentally secure, much more flexible and lightweight, and more impact-resistant than the standard PVC-jacketed conduits so widely used in the North American market. Clearly, it’s time for an upgrade.