Interested in linking to "Taking the heat for replacing a brush hot"?
You may use the Headline, Deck, Byline and URL of this article on your Web site. To link to this article, select and copy the HTML code below and paste it on your own Web site.
By Loren Jones, Controls Technician
’ve worked a lot of places in my career, and I’ve pulled some spectacular stunts, but nothing tops this one. I was working at an aluminum mill in southern California as an electrician and it was my first experience on that side of the trade. I’d received extensive training in electronic instrumentation and had been working as an instrument technician and electronics technician for five years. As far as I was concerned, working as an electrician was a step backwards. Okay, I was conceited, but I’d only been given the job because I had a lot of drive experience.
Anyway, I had been on the job for about three months and was already on shift alone. I learn fast. I usually only need to see something done once to have it. So I was alone on the knockout shift: two nights, one off, one day, two evenings, one off. See why they were in a hurry to throw me to the wolves?
I received a call at about 2 a.m. that there were sparks inside a motor at one of the casting lines. I quickly made my way over to it and the operator pointed out the sparks. They were visible through the ventilation grating over the commutater. I checked the name plate and found out it was a 5 hp DC motor. The motor was still running and the operator asked if there was anything I could to without shutting him down.
I mentioned I was conceited, right? I said, “Sure, no problem.”
I pulled the vent cover off of the motor and took a closer look. The sparks were caused by one of the brushes being loose and bouncing on the commutater. I looked closer and found that the pin that held the hold-down spring had sheared, and the spring wasn’t holding down anything. So I decided to change it. Without shutting off the motor.
I may be conceited, but I’m not stupid. The brush lead was held by a Â¼-20 bolt, so I put on a new pair of leather work gloves and put two layers of electrical tape on my wrench. Then I carefully loosened the bolt and used my needle-nose pliers to remove the brush. Then I loosened and completely removed the two bolts holding the brush-holder and eased it out. So far, so good, and the motor still had two brushes in that set.
I took the brush-holder back to the maintenance shop and repaired it. It took a while, and I had to scrounge parts, but I eventually had it in like-new condition. Then I had to put it back in.
Taking it out had been fairly easy. Getting the bolts back in place so I could tighten them down was a real pain. I ended up having to tape them to my needle-nose pliers and do a contortionists act to get them in place so I could tighten them down.
Once the holder was in place, it was easy to put the brush back in. I even got a commutater cleaning stone and burnished it a little to clean up the marks from the sparking. I was feeling pretty proud of myself when 7 a.m. rolled around. The four senior guys who were on straight days came in and we sat down for some coffee while I told them what had happened overnight.
One of these days I’ll learn to keep my mouth shut. I told them what I’d done, fully expecting to have praise heaped on me. You could have heard a pin drop.
The senior electrician leaned forward and asked, “You did what?” very softly.
“I fixed a broken brush holder without shutting the caster down.”
“You can’t do that,” the next most senior of them said harshly.
“Sure you can. All you have to doâ€¦”
“You. Can’t. Do. That.” Three of them said together.
I was indignant. Here I was, expecting to be praised, and they are telling me I can’t do what I did. “Well maybe you can’t, but I did.”
The senior electrician reached over and grabbed my arm. “It is against the safety regulations to work on energized motors. You should have had them shut down, then locked out the drive before working on it. You’re going to get your dumb a__ fired!”
“Um, for what? I really was safe. I insulated everything and wore my gloves. I never even felt a tingle.”
“Because it was energized. You don’t work on energized equipment. Energized equipment makes you really dead really fast.”
The junior guy of the four grabbed my shoulder and made me look at him. “If the foreman finds out, you’re history. If you get fired, I go back on shift, and I don’t want to do that.”
I was beginning to feel really put upon, so I said, “It’s no different than changing a 480 volt high-pressure sodium fixture hot.”
Did I mention that I really need to learn to keep my mouth shut?
ControlGlobal.com is exclusively dedicated to the global process automation market. We report on developing industry trends, illustrate successful industry applications, and update the basic skills and knowledge base that provide the profession's foundation.