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.
@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.
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.
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?
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