What jacket material is required?
A cables outer jacket not only must withstand mechanical stresses associated with continuous-flex operations, it must withstand environmental stresses, as well. Such stresses include contact with aggressive fluids (e.g. oils, cleaning fluids, coolants, chemicals, etc.), extreme temperatures, abrasion, sunlight if operations are outdoors, or ocean salt for offshore operations.
The most common jacket types found in industrial applications include polyvinyl chloride (PVC), thermoplastic elastomer (TPE), and polyurethane (PUR).
PVC jackets are best suited for static applications or applications where cables are flexed minimally. Unfortunately, PVC-jacketed cables tend to move around too much within the track, which increases their exposure to potential abrasion. Coupling their low abrasion resistance with poor elasticity prevents them from being used in dynamic applications that require large cycle counts, e.g. 5 10 million flexing cycles. PVC-jacketed cables can perform in temperatures ranging from 0C to 125C, and resist most coolants, fluids, and sunlight.
TPE jackets are resistive to more chemicals than PVC, can be used in continuous-flex operations, and operate effectively in temperatures up to 125C. TPE jackets are preferred in such industries as automobile power train manufacturing, which exposes the cables to numerous cutting fluids and lubricants.
PUR cables are more elastic, which allows them to stay on the perimeter of a track and less likely to collapse to the inner midpoint of a track. This reduces overall cable movement within the track and minimizes abrasion. PUR cables can operate in temperatures between -40C to 80C, and withstand abrasions, cuts, tears, and many chemicals, making it the ideal jacket for rugged industrial manufacturing operations.
Is shielded or an unshielded cable required?
Electromagnetic interference (EMI) is prevalent throughout the factory floor. To minimize additional noise generation, which affects many other systems like radio and data communication, power cables are constructed to be electromagnetic compatible (EMC). Communication cables are shielded to prevent the effects on the data transmitted from EMI and also paired and individually shielded to prevent cross talk and coupling. Cable shielding uses either a braided, spiral, or metal-coated mylar shield.
Shielding wraps around each conductor to mitigate noise by 85 percent to 100 percent depending on the configuration. The max shielding a braided shield can be is 90 percent. Spiral shields can be 98 percent, while metal-coated mylar can deflect 100 percent of EMI. In some applications, such as those needing servo cables, double or even triple shielding is required: around individual conductors, around twisted pairs, and around the entire cable.
In applications where EMI radiation is not a concern, non-shielded cable variants are acceptable to control or provide machine feedback during plant operations.
What approvals are needed?
Knowing where the cable will be operating is important because each country has unique requirements that must be met before the cable can be used in the machine. Country approvals and certifications govern appropriate cable materials, ampacity (electrical current a conductor carries without failing), operating temperature range, flexibility, jacket thickness, shielding requirements, and flame resistance, to name a few. If machines are installed domestically, the cable will need UL approval. However, if the machine is constructed for operations ex-US, approvals such as CSA, IEC, CE, VDE, CCC, and GOST-R, etc. will be needed. Specifiers should look into finding cables that contain multiple approvals, which saves on inventory costs since fewer cables will need to be stocked.
Markus Dannheim is president of HELUKABEL USA.