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Connecting with cables and carriers

July 1, 2011
Industry experts discuss what's new in the world of connectivity and provide useful advice on keeping cables and carriers up and running.

What's new regarding cables and carriers?

Larry • KabelSchlepp: Cables, carriers, and related components have evolved over the years to accommodate ever-increasing demands for higher cycle speeds, longer life, and greater reliability. Specialized designs can address specific challenges such as clean room use, elimination of operating noise, and reduced installation costs. Innovations in materials and manufacturing processes include the use of nanotubes in plastics for greater strength, and electrostatic discharge for applications where explosion hazards exist. Processes such as simultaneous co-molding of different materials allow single-piece carrier links that have a rigid frame made of one material for high strength, and flexible crossbars made of another material for easy cable installation.

Kevin • Northwire: Other new technologies and materials in the cable world include in-process control devices (laser and x-ray technology), low smoke zero halogen and halogen-free flame retardant (HFFR) insulation and jacketing materials, and improved tensioning of primaries and cabled core during cable manufacturing. Improved shielding technology is also being used on connectors.

Joe • igus: Some of today's new tools make the process of specifying a cable carrier system much easier. For example, we offer an online product selector and cable carrier configurator. With the product selector, users can quickly select the right cable carriers or continuous-flex cables by simply entering a few application parameters. With the configurator, users are able to easily build a cable carrier with cables and internal separators online. CAD files, parts lists, and quote requests can all be quickly generated, saving engineers a lot of time.

How can the right cables and carriers maximize productivity?

Joe • igus: Choosing the right cable carrier — and pairing it with appropriate cables for the application — is crucial. While steel cable carriers still dominate in some industries, such as on boom trucks and in the steel-working and mining industries, plastic carriers can replace steel in almost any application to maximize productivity. Plastic cable carriers have replaced steel on most types of automated machinery in recent years because they are lighter weight and enable a higher number of cycles, faster speeds, and increased production throughput.

Another way to avoid failure and downtime is to make sure the cables housed in the cable carrier are designed for continuous flexing. If a cable that can't handle high-flex environments is used in a dynamic application, loss of continuity, insulation damage, and jacket abrasion can result, leading to machine failures and downtime. Using a pre-harnessed cable carrier system can also maximize productivity. If users receive a cable carrier system ready to go right out of the box, there's no need to fumble with cables, attach connectors, or assemble separators, mounting brackets, and other accessories.

Larry • KabelSchlepp: Today there's an increasing trend for cable and carrier suppliers to offer bundled “total systems” that provide all necessary components, perfectly matched to the application and environment. By providing a complete system, manufacturers can reduce installation times and associated costs, while reducing the risk that any subcomponent might not be suitable for the application.

Tell us about some emerging technologies.

Kevin • Northwire: Many new and emerging materials are under development, such as carbon nanotube technology, alternatives to wire shielding, improved low smoke zero halogen materials, and renewable materials for use in polymer design. A lot of work is also going into improving the purity of the dielectric, detecting minute flaws in cable surface, and improving connectivity (soldering and shielding) to increase signal and data transmission speed and accuracy.

What about best practices regarding specification and sizing?

Dave • Alpha Wire: If the size of the cable is approaching the maximum size for the carrier, avoid the temptation to use a cable that might be just a bit too large for the carrier and instead use two separate cables. Understand the difference between a flexible cable (a cable where the property of being limp or flexible is a significant design feature) and a high-flex cable that is specifically designed for continuous flexing. Not all flexible cables are optimal for continuous flexing. The rated flex life of the cable should be commensurate with the application.

Larry • KabelSchlepp:

Don't overfill the cable carrier. As a rule of thumb, allow an additional 10% of the OD of buffer space for cables and an additional 20% of space for hoses. Overall, the maximum cavity fill should be no more than 60%.

Unspool the cables and allow them to relax to relieve any tension or twisting before installing them in the carrier.

Consider environmental factors such as exposure to heat, cold, radiation, UV, salt water, and corrosive chemicals, and specify accordingly.

Bend radius is very important when specifying a cable and carrier system. Select cables or hoses that have a minimum bend radius that will fit within the operating envelope and that are designed to withstand the stress of continuous flexing. Then make sure that the cable carrier's bend radius is equal to or larger than that of the largest cable.

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Kevin • Northwire: The design engineer or cable specifier must know the system outputs and constraints so that the correct information gets translated to the cable design engineer. This includes electrical performance requirements (capacitance and impedance), diameter constraints, environment, bend radius, and type of connectivity.

Joe • igus: Make sure the first question your cable carrier manufacturer asks is, “What's the largest cable or hose in your system?” This will determine the minimum size of the cable carrier. To this number, add proper clearance — 10% for cables and 20% for hoses — and the resulting dimension will be the minimum inner height of the carrier.

Choose a snap-open cable carrier whenever possible. This allows access to cables with crossbars that snap open at any point along the carrier. If debris or other external conditions are an issue, the tube-style cable carrier replaces the crossbars with lids to fully enclose the carrier and provide complete cable protection. This style is especially useful in applications where woodchips, metal filings, and other debris are present.

Let the environmental conditions of your application determine which style of carrier to use. If debris such as woodchips or metal shards is present, or if the application is in a dirty or contaminated area, an enclosed tube is best. An open crossbar carrier is lightweight and facilitates easy inspection and replacement of cables, whereas tube carriers offer removable lids for cable access. Also consider whether the application is underwater or comes in contact with liquids. Plastic cable carriers can be a good choice here because they will not corrode and are resistant to chemicals.

Any advice for harsh environments?

Kevin • Northwire: To ensure the best cable performance over a known time period, the user must communicate all information regarding the application environment, how the cable will be handled (static environment versus continuous movement), ambient temperature, and whether or not harsh chemicals will come into contact with the cable.

Joe • igus: It's important to gather all the necessary technical data prior to contacting a cable carrier vendor. This includes length of travel, what cables or hoses will be installed, the size of cables and hoses and how much they weigh, any environmental factors such as debris, heat or chemicals, and speed and acceleration. For harsh applications, plastic cable carriers can be a great option. Due to their high-performance plastic construction, they are corrosion-resistant, lightweight, and maintenance-free. They can be used in many harsh environments including offshore applications such as oil rigs, as well as brick plants, coal-burning power plants, road construction vehicles, refuse incineration plants, tunnel drilling machines, steel mills, waste handling, and mining. They can also handle heavy loads, high speeds, and long distances.

Larry • KabelSchlepp: Steel cable carriers can withstand exposure to extreme heat and cold, radiation, high winds, and other environmental factors that are beyond the recommended operating parameters of standard carriers made of plastic. Other options such as stainless steel, special plating, and surface treatments can further expand the steel carrier's suitability for use in environments such as offshore drilling where their resistance to corrosive seawater and the ability to support extreme loads make stainless steel carriers an excellent choice. That said, plastic cable carriers have also made great advances in terms of material and design that allow them to operate in a wider range of harsh environments that were once only possible with steel carriers. Certain cable carrier design features can further enhance a system's suitability for harsh environments. Options like tube-style carrier designs can provide added protection, shielding contents from damaging exposure to things like red-hot metal chips and corrosive chemicals.

Any words of wisdom for maximizing cable life?

Joe • igus: Choosing a cable specifically designed for continuous-flexing is crucial in a dynamic application. End users can maximize life and avoid downtime by making sure that cables have certain attributes. The cable should have a strain-relieving core filled with a high-quality, high tensile strength core to protect the twisted conductors from falling into the center. Conductor structure, core insulation, inner jacket, shield design, and outer jacket all need to be taken into consideration. Also, correct cable distribution within the cable carrier will increase cable life. The key advantage of a cable carrier is that bus and motor cables, pneumatics, electrics, and hydraulics can all be guided safely in one system. Correctly arranging each cable and hose within the chosen cable carrier according to the recommended spacing requirements is vital to prolonging the system's service life.

Dave • Alpha Wire: This may seem incredibly obvious, but make sure to follow the manufacturer's recommendation on minimum bend radius, both within the carrier and also as the cable is dressed out. We've seen situations where the violation of the minimum bend radius — and location of the bend — led to premature cable failure. We also recommend a quiet zone or a length of at least 50 times the cable OD where the cable exits the carrier. Within this zone, cable bends should be avoided or minimized, so that the forces present within the cable are allowed to dissipate before encountering a restriction.

Larry • KabelSchlepp: Select a cable designed for use in carriers. These cables typically use special jacket materials and core designs such as bundling or layering that allow them to bend in a tighter radius and continuously flex to accommodate a high number of machine motion cycles over the life of the system. Be sure to use proper strain relief at the ends of the cable carrier. Never tie, wrap, or clamp cables in the middle of the carrier. Also, properly partition the cable carrier cavity to separate and organize cables and hoses to evenly distribute weight, organize contents, and keep smaller cables from tangling.

Northwire provided 6,000 ft of its Underwater Cable for a casino application within a water theater, where the cable controls and powers moving platforms and water jets. The specialized cable is designed for use in freshwater or saltwater as well as chemicals, solvents, and other fluids.

Industry expertise

Joe Ciringione
igus Inc.
(800) 521-2747

Kevin DePratter
Northwire Inc.
(800) 468-1516

Larry Harvey
KabelSchlepp Division
U.S. Tsubaki Power Transmission(800) 443-4216

Dave Watson
Alpha Wire
(800) 52-ALPHA

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