Maintaining connections

There are plenty of issues that cause network headaches, but never assume your electrical subcontractor is familiar with routing and terminating network connector cables, even if they do it all the time.

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Motivated Maintenance
Even industrial connectors eventually can succumb to environmental conditions and fail. Review your preventive maintenance procedures for adequacy based on your maintenance and repair history, the existing environment the connection is in, and the criticality of the application.

 “There’s a tendency to view maintenance as a cost,” explains Bisbee. “It’s actually an investment. Downtime is a cost, and maintenance is what you do to prevent it. However, you have high ROI maintenance only when you have a complete program with correct procedures and proper maintenance intervals. Think of the millions of dollars indirectly running across the typical industrial network each month. Does endangering that revenue by ‘saving money’ through failing to maintain a lowly connector seem like a good idea to you?”

At a minimum, our experts say required maintenance functions should include:

  • Infrared inspections to detect voltage loss across connections.
  • Insulation resistance tests to ensure insulation integrity along an entire wiring or cabling run.
  • LAN tester verification of critical runs.
  • Visual inspections in junction boxes.

Also, maintenance should never re-torque bolted connections or screw terminals because this actually weakens the connection. Replace crimped connectors, rather than re-using them.

What About Wireless?
As an alternative, wireless technology can reduce connection problems, right? Not in the real world. “For every wireless access device connecting to the network, there is a wired signal connection that can fail,” LaBree says.

A wireless system propagates signals from access points, which physically connect back to equipment via cabling and connectors. The typical application requires many access points because each point has a range of only 30 m. You might need more access points to overcome obstacles and blind spots. It’s easy to forget this, and consequently minimize the importance of the connectors and terminations. This all but guarantees signal degradation.

A site evaluation is a good thing to do before implementing wireless. “In large industrial applications, you still might have to contend with cable length limitations when installing data lines to the wireless access points,” explains Charles McElhose Jr., senior network engineer with Craftix Technical Solutions. “Per EIA/TIA-568 standards, the end-to-end connection between network devices shouldn’t exceed 100 m. Lines that feed wireless access points are no exception. You'll also need to run power.” Based in Baltimore, Craftix is an IT services firm that provides data cabling and network engineering services in the Baltimore-Washington corridor.

“I’m constantly amazed at the amount of wire and connectors necessary for a wireless network,” notes Dave Lagerstrom, connectivity division director at Turck Industrial Automation.

Wireless eliminates some cable runs, but the number of connections might not decrease and might even go up.”

That’s not all. “Security issues with wireless are intense,” adds Bisbee. “Wireless has its place. I’m just saying there is no free lunch. What you might save in connector costs can come back in security implementation and administration costs.”

McEllhose agrees with this projection. “Wireless opens potential security threats,” he says. “We routinely advise adding a firewall between the main LAN and the wireless LAN, so rules can be created to prevent wireless traffic from accessing systems on the wired LAN.

Fiberoptic Alternative? 
The use of fiberoptics is expanding because it offers high bandwidth, and isn’t susceptible to electromagnetic interference. However, there’s another advantage due to its simplified code compliance.

The National Electrical Code (NEC) covers fiberoptics in Article 770. Chapter 3 of these NEC rules imposes some fairly complex requirements designed to prevent conductors from overheating. Because fiberoptics aren’t current-carrying conductors, they’re exempt from these requirements (with a few minor exceptions). Of course, where a cable or raceway mixes fiber and copper, you get back to complying with current-carrying conductor requirements.

While using fiberoptics simplifies code compliance, it complicates termination procedures. Terminating to fiber is hard to do well under field conditions. The tools alone make this point clear. You typically need a fiber cleaver or scribe tool, cable and fiber strippers, polishing films, a polishing tool, a microscope, specialized crimpers, an epoxy syringe, and even a curing oven. (The sidebar below provides some helpful tips.)

If you mess up a fiber termination, the connection will probably still work, but will have reduced bandwidth. Mess up several terminations, and the entire system will lag for “no apparent reason.”

Ordering fiberoptic cables with connectors preinstalled would seem to solve this problem. After all, the factory—unlike the field—has a stable working environment. Assembly technicians can use the same procedures and tools each time. However, this isn’t the cure-all it might seem to be. For example, you must know the cable length within a fairly small margin of error because providing a glass guide for light creates routing and bending problems you don’t have with copper conductors.

Think Strategically
Manufacturers have all kinds of solutions for industrial networking connections. No one solution is best, except the one that meets the connection requirements of your particular application.

Schaible sums up how to prevent connector and termination problems. “Research and specify your connector and cabling systems, just as you would the hardware components. Never leave these details to chance.”

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