By Bob Mack
I have worked in heavy industry, steel processing, most of my career. Wire connections are at the top of my hot list. No machine control, no matter how sophisticated, is better than the sum of all signal connections. It is a foundation, like the concrete your home sits on.
We in engineering live with our work/designs from cradle to grave, and when I decide on a connector with a contractor or integrator/machine builder, the discussions can get heated.
I consider them in reverse—what they will suffer during a lifetime, what their condition will be when we finally put that machine down. All connectors are good when you look at them in a sample case. It’s the application that will get you. Beware the new technology that’s cheaply built and not yet proven over time in the real world.
You want the most rugged and, over many years, reliable device you can find. Your contactor or vendor wants the best price, the least installation time and the simplest design available. Yet a $5 device has cost a single facility as much as a quarter million dollars in just one month in damaged machine controls and repairs, and those are costs we know of.
Many years ago, we allowed a machine builder to supply control cabinets using spring-type insulation-displacement connectors for their time-saving benefits. We agreed to it because the cabinets were in a controlled environment, meaning the room was sealed and air conditioned and we all agreed at the time it was a safe application—low voltage, low current.
Once you get a machine project up and running you lose track of decisions until that day when the bottom falls out. The process line is down more than it’s up, and your company is losing business because the machine just can’t stay in operation for more then a couple of days, and you get that phone call asking for help. You know the local maintenance people personally and you trust them when they say they’re doing their due diligence in PM work. When you try and discuss the problems to get some clue where to look, it seems that everything is just broken and there’s no common thread to the endless array of trouble.
You have to ask yourself what could be common to all these breakdowns. They seem to appear and disappear without warning all across the entire machine. It just seems the machine has developed a mind of its own. There is no way you can solve such a massive set of problems remotely, so you pack your bags and head off to the site. Everyone has a horror story to tell, so we just pick one and go after it with all the experience we can gather from my own background and anyone who will talk to us.
Every terminal in every control cabinet was replaced. Everything had to go. There was no way I wanted more phone calls that the machine is broken and find another bad connector. I don’t believe our CEO would be real understanding when he learned that a $5 piece of hardware that I was supposed to replace last week broke again this week and just cost our company another $1,000 per hour of machine downtime.
This was part of a bigger-picture group of control problems that all pointed to bad connections. Improper wire size also was a contributing factor in the IDC technology. We replaced many standard screw terminals with terminals that would accept crimped ferrules on the stranded wire. The IDCs were all replaced with touch-safe screw clamp terminals that accept one wire only per terminal sized for exact wire size.
The day those spring terminals were approved really hit home in a way that I don’t think anyone involved could have ever imagined. That’s the tough part. How do you hold down the upfront costs of the project without taking too much risk? I have no problem with the time and cost. But the bean counters many times only see the initial hard costs and don’t realize the potential for disaster.
So my question to you is just what do you think of those connectors in the window, and what do they really cost? Answer carefully, because they are the foundation of your best control system.
Bob Mack has 21 years of experience with steel processing machines. He is controls engineer at Steel Warehouse in South Bend, Ind., and a member of the Control Intelligence Agency Virtual Brigade.