Field technician: Where does the grey wire from terminal 21 go?
Engineer: Grey? That wire should be light blue.
Field technician: All the wires I see are grey.
This is what happens when the talented but willful production team takes engineering directives as suggestions. Decisions regarding component selection are informed by specifications, regulations, physical laws, and personal preference. Regardless of how a decision was arrived at (fortune cookies, dice rolling, asking the janitor, etc.), it is not the place of production to second-guess engineering. If it was, then they would be the ones in a windowless office under flickering fluorescents, surrounded by productivity-increasing bland grey furnishings.
I am not talking about problems reported back to engineering for correction. I am talking about laborers thinking they will use a solenoid in place of the one you specified, because it looks similar and has the same voltage rating, and then not telling anybody.
Excuses like "I ran out of blue wire," "It's almost identical," and my favorite, "That's not how we used to do it," are not valid excuses. I can't even think of a valid excuse. In this particular case, a multimillion-dollar fire suppression system was to be installed throughout a manufacturing facility. This location routinely bursts into flames, they use kerosene as a lubricant. Fire breaks out, CO2 floods the area, workers have just enough time to escape certain suffocation. The control panels for this facility were being repaired and upgraded, when some questions arose. As they gave the opening exchange, above, they had replaced control panels wiring with some grey wire that looked "like the same stuff." After an argument over the wire, the engineer's demands won out. The project was on hold until the proper wire was obtained.
How do we assist the field tech or customer when documentation does not match the physical design in the field? An adulterated design which may later require the ministrations of a technician because production took liberties during construction.
Excuses only come up when critical thinking is absent. I'm sure we all have stories about others but how many are willing to admit that we've done it too?
The gist of the article is about unapproved substitions, and I agree 100% with the author. An unapproved substituion is one reason for the KC Hyatt skybridge collapse we discussed several months ago.
The specifics of the article bring up a slightly different question. Should color be a differentiator? I know fully well the color standards for wiring, use it in my control panel designs, even agree that such a standard makes a ton of sense.
But what about color blindness? Somewhere between 5%-7% of the male population has some form of color blindness. For those, labeling and positioning are the only way to differentiate wires or controls.
@TJ McDermott: Being "colorblind" doesn't mean being unable to see colors; it just means that it's more difficult to differentiate between certain colors.
I have deuteranopia, which is one of the most common forms of colorblindness. While most people have three types of color receptors (red, green, and blue), my eyes only have receptors for red and blue. Since I don't have specialized receptors for intermediate-wavelength colors, they don't appear as distinct to me as they probably do to you. For example, the colors gold, light orange, and light green all look pretty similar to me.
This site has some good pictures that illustrate how colorblind people see things.
You're definitely right about labelling wires. Whenever I have to deal with color-coded wires (red and green; blue is not a problem for me), I usually have a non-colorblind person tell me what color the wires are. Then I attach small pieces of tape labelled "RED" or "GREEN."
I suppose that if someone wanted to make my life more difficult, they could either lie about the wire colors, or else switch my pieces of tape when I'm not looking. Thankfully, I've managed to get along well enough with my co-workers that it's never happened.
Interestingly enough, a small percentage of women are said to be tetrachromats, meaning that they have four types of color receptors instead of just three. That would make them better able to distinguish between colors than regular people.
Interesting topic regarding color differentiation. Regarding wires, you just can't be in industry very long without running into stuff that is not color-coded according to traditional colors (ex. red = Vcc; black = GND). Almost like whoever manufactured it was operating from an entirely different system but in reality was probably using wire that was most readily available to them. What is even worse is if they use a different gauge because they had the "right color" in that gauge - especially if they go the wrong direction for the current rating! I wholeheartedly agree that production should seek an ECN before arbitrarily making any changes, but it depends on the specific production facility and management as to whether or not that will be enforced..
Getting back to those folks who are colorblind, I can see how other methods of distinguishing wires would be helpful. Back in my school days there was a guy that was color blind so he couldn't look at a resistor to tell its value - he almost always had to ohm it out. And different shades of the same color also cause confusion among folks who are not colorblind...
The color does matter, in a way. If substitute wire is used in a system, it may not work. In this case, relying on someone to choose correctly, is chancy. I have another story coming out where someone installed 4km of wire that "looked the same" as what I suggested. There was a difference between the speaker wire they installed, and the shielded larger gauge wire that it needed.
However, taking into account for someone's color blindness is something I did not consider. If that is the case, perhaps a second person should be consulted. I assume that color blindness is something a field tech or line worker should admit? I will be sure to ask about this issue in the future.
Cabe, absolutely, the standards for wire color coding should be followed. They make sense! But during retrofits and upgrades, I expect to find contrary or insanity for color coded wires. Opening a panel often reveals a rat's nest instead of neat, orderly wire ducting.
Color coding can be a pain in the neck too, when it's a large-count multiconductor cable. Is that wire red with a white trace or white with a red trace?
Adding a second person to the process means adding cost.
Asking an employee to own up to a weakness that could cause them to be discriminated against is simply not going to happen.
Interesting discussion on color blindness and tetrachromatics. As neat as a tetrachromat might be, I don't think they would perceive more colors, just perceive the colors differently (since the different cones are somewhere between red and green responsive). Makes me wonder if anybody might be responsive to IR or UV light?
But back to the article: I've had similar issues with our production department (when we still had one). Occasionally we would get a change request from production, on product we had been making for years without issue. When we (Engineering) would inquire what had changed, the answer would be "nothing". They had been building the product as we wanted them to (but not to the drawings/BOMS). Eventually, someone would actually look at the drawing or BOM and halt production until the change request was processed. Of course, this always happened when an important schedule date was looming.
These sort of designs are created and prototyped by engineers and technicians. In our world, color is everything and we have a wide range to choose from.
The installers in the real world are electricians, whose color range is more limited. They also avoid this very sort of problem through numbered wires, even if they are all blue.
This difference should be considered by desigmers who can not be sure their equipment will always be installed by engineers or technicians.
Indeed. I'm red-green colorblind and have to ask for help from time to time--or use really bright lights. Just this Sunday I was mending a cable that the puppy had chewed through in the car. She severed all seven wires, and shortened three of them.
The light blue was easy, as was the orange, and the black, and the black-with-white stripe. I had to ask for help to confirm that the remaining ones were a brown and two identical dark-grays.
OTOH it's very easy to work on my Whirlpool drier which labels each end of each wire with a distimctive identifier and has matching identifiers on the schematic helpfully placed on the back of the machine. These folks are a model for friendly design.
Having built, instlled and serviced equiptment I have found that it takes very little time to do it right the first time, and it makes for much more work to take a shortcut. Not having the right color wire generally means that someone chose to cut back on an order to save a few dollars and someone in the field wants to get teh job done so they use what is at hand rather than what was specced. It also seems that the panel that was wired neatly is generally wired correctly and seldom needs to be accessed. Conversly, the panel than was wired poorly is the panel that will be accessed again and again. It would seem that the guy who cares to do it neat also cares to do it correct.
Having the correct wire colors also saves time when it comes to repairs. Instead of having to look at a bundle of 100 wires, you have a bundle with 20 wht/blu, 25 blu, 15 red, 15 orange,a few white and the rest are green. If they are all the same color it is abotu certain that he wire you want will be the last one you trace out.
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