Careful installation critical to trouble-free performance
Dave Harrold, senior editor -- Control Engineering, 11/1/2001
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In an industrial environment, wire and cable have a lot in common with tubing-each is exposed to every industrial 'nasty' anyone can think of, and each is installed and forgotten until a connector fails.
When a tubing connector fails it's seldom an instantaneous, catastrophic failure. Usually the connector experiences a small leak that becomes progressively worse over time. Depending on the material flowing through the tubing, the leak can become a workplace or environmental danger. What doesn't happen with tubing leaks is media cross contamination.
Cross contamination
When you think about it, cross contamination is exactly what can happen when a wire or cable connector is poorly installed or the connector becomes loose and EMI/RFI/ESI (electromagnetic interference/radio frequency interference/electrostatic interference) adversely affects the primary signal. This is called 'signal interference' and often goes undetected for months, even years.
This mention of 'signal interference' seems appropriate because, according to a recent wire, cable and connector survey conducted by Control Engineering and Cahners Research, loose connectors was listed by respondents as the number one recurring problem. (See 'Recurring Problems & Challenges' diagram.)
According to technical data provided by Alpha Wire (Elizabeth, N.J.), there are essentially four sources of signal interference.
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Static noise occurs when an electrical field distorts the signal and can be mitigated using continuous foil shields and appropriate shield grounding techniques.
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Magnetic noise comes from large ac motors, transformers, and knife switches and can set up current flows in opposition to the instrument signals. Use of twisted-pair signal wiring is the easiest and most common means of eliminating magnetic noise interference.
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Common mode noise results from currents flowing along the instrument wire or cable between ground points of different potential, an especially frequent problem found in geographically distributed, but physically connected control systems. Mitigation requires a carefully designed and properly installed power and grounding system.
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Crosstalk refers to the superimposing of pulsed dc or standard ac signals between two or more nearby wires or cables. The most effective means of eliminating crosstalk is the use of individually shielded twisted-wire pairs.
A closer examination of 'Recurring Problems and Challenges' data reveals several events could likely be traced to poorly installed or loose connectors.
Who, where, what
During this past June, 7,000 Control Engineering subscribers were invited, via e-mail, to participate in an online wire, cable, and connector survey. Of the 510 responses, 309 are involved in specifying, recommending, and/or buying wire and cable for in-plant (83%) or OEM (original equipment manufacturer) (23%) requirements. By far, processcontrol (70%) and machine-control (69%) applications are the biggest users of wire and cable among survey responders.
The most-specified wire and cable product was twisted pair (94% of respondents). Next, 75% require wire and cable be chemical/oil resistant. The number 68% came up twice in the area of wire and cable applications, first wash-down locations and again in continuous flexing/robotic locations. The survey didn't explore if connector looseness problems were related to wire and cable flexing caused by wash-down and/or continuous flexing/robotics, but it seems like an area wire, cable, and connector manufacturers might want to study further.
Mind your P's and Q's
Each time Control Engineering conducts a reader survey, we ask respondents about supplier selection criteria, and each time the results boil down to users want to do business with high integrity companies-those that produce quality products, support the products they sell, and are easy to do business with. (See 'Supplier Selection Criteria' diagram.)
Wire, cable, and connector products
An expanded version of this product focus article with additional product write-ups is available at www.controleng.com. For more information on industrial wire, cable, and connector products, circle the following numbers, or visit www.controleng.com/freeinfo. For a wider listing of manufacturers, go to Control Engineering Buyer's Guide at www.controleng.com/buyersguide.
DataTwist 600e exceeds category 6 specs
St. Louis, Mo. -Belden recently introduced DataTwist 600e, a UTP cable engineered to perform well beyond the 250 MHz proposed in category 6 standards. DataTwist 600e's unique manufacturing process ensures twisted pairs maintain uniform conductor-to-conductor spacing to minimize impedance mismatches, return loss, and crosstalk, allowing Belden to guarantee DataTwist 600e's performance to 600 MHz. User benefits from improved cable performance are realized in a stronger, higher quality transmitted signal reaching individual receivers. www.belden-wire.comBelden
Alpha Wire meets automotive industry needs
Elizabeth, N.J. -Alpha Wire recently introduced Xtra-Guard, a family of high-performance electronic cables designed specifically for critical flexing industrial applications including high speed 'C' tracks. Xtra-Guard cables can withstand oily environments, protect against EMI, and are available in bulk and 'cut-to-length.' Xtra-Guard's high-flex mini diameter data cable is a multi-conductor cable especially suited for connecting industrial electronics, controllers, sensors, and actuators. Available in shielded and unshielded configurations, Xtra-Guard's high-flex torsion cable is designed to withstand the random flexing and twisting commonly associated with robotic applications. www.alphawire.comAlpha
Multi-conductor cable for harsh environments
Fairfield, N.J. -Olflex 190 multi-conductor control cable's specially blended oil-resistant insulation is said to provide optimum resistance to mineral- and synthetic-oils and water-based coolants, and is suited for wet and dry conditions. Olflex 190 has passed requirements of the VDE 0472 Section 803 oil test and has been UL approved, CSA certified, and is CE conforming. Olflex 190 features include: 600 V working voltage; -40 to 194 °F (-40 to 90 °C) temperature range; a bend radius of 15X cable diameter; and is available with conductor sizes from 2 to 20 AWG. www.olflex.comOlflex
IDC technology cuts costs
Richmond, Va. -Weidmuller recently expanded their range of compact 3.5 mm pitch connectors for printed circuit boards to include insulation displacement connection (IDC) technology. Weidmuller's Blidc 3.5 and Blidc B3.5 plugs eliminate the need to strip insulation and crimp ferrules, thus reducing installation time and associated costs. The Blidc 3.5 is available in 2- to 16-pole versions with or without mounting flanges. The Blidc B3.5 is designed for wiring bus systems, can be installed anywhere along the wiring, ensures safe and secure connections, and enables uninterrupted 'daisy chaining' of bus signals. www.weidmuller.comWeidmuller
Preconfigured cables cut installation times
Harrisburg, Pa . -Available for most popular PLCs, Phoenix Contact offers controller cabling solutions consisting of a replacement cabling adapter that plugs onto the PLC card and replaces the existing screw terminals; a cable assembly in various lengths; and an interface module that can be a simple pin-to-pin design, a relay interface or sensor input, or designed to meet specific application requirements. With the Phoenix Contact controller system cabling, terminal blocks are replaced by a Vareioface interface module resulting in claimed labor savings of as much as 75%. www.phoenixcon.comPhoenix Contact
Cable qualified for classified locations
Ramsey, N.J. -Okonite's continuous lightweight exterior (C-L-X) cables have earned certification by the ABS for shipboard use and many C-L-X metal-clad cables are qualified for use in Class I, II or III, Divisions 1 or 2 hazardous areas. C-L-X cables are designed specifically for use on feeders and branch circuits in industrial power distribution applications; may be installed in exposed or concealed, wet or dry locations; can be direct buried or embedded in concrete; and are recommended as an economical alternative to wire in conduit. www.okonite.comOkonite
Anixter receives 2nd UL certification
Skokie, Ill. -Anixter's Levels Lab (Mt. Prospect, Ill.) recently completed a rigorous, independent, third-party audit under Underwriters Laboratories (UL) Certification Services and received a second UL certification that permits Anixter to analyze manufacturing quality and performance levels of network cabling and components. Using Anixter's Levels Lab, miles of copper and fiber optic cable, hundreds of different connectors, patch panel ports, and patch cords, Anixter can test and analyze key network performance requirements and identify problems before they reach customer installations. www.anixter.comAnixter
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