Power Plant Manhole Mania

Originally posted February 1, 2013:

It is vitally important that a manhole cover be round. By just being square or even oval, it could mean death to some unsuspecting electrician. You see, only a perfectly round manhole cover will never be able to fall down into a manhole. No matter how hard you try, you just can’t fit a bigger circle through a smaller circle. An oval or square cover could fall through the hole when turned just right but not a round one. A typical cast iron manhole can weigh up to 500 pounds.

Here is a manhole cover turned upside down.  Because of the way it is shaped, when you push the cover over the hole, it falls right into place.

Here is a manhole cover turned upside down. Because of the way it is shaped, when you push the cover over the hole, it falls right into place.

Not long after becoming an electrician, and shortly after the Rivers and the Rose story that I mentioned last week, we had a cable really go to ground between the main plant and the coalyard. The cable that went to ground was called a 500 MCM cable. What this means is that 500,000 circles of 1 mil (or one milli-inch) in diameter can be put in a circle that is 500 MCM in diameter. A typical 500 MCM cable is good for a 400 amp load at 6900 volts.

500 MCM cable.  Over 2 inches in diameter.

500 MCM cable. Over 2 inches in diameter.

For large industrial circuits, 3 phases of electricity are used instead of just one like you have in your house. With three phases of electricity, you have a constant amount of power being applied to the entire circuit at all times. With a one phase circuit, you have zero power 120 times every second. So with any “decent” power circuit, you have 3 phases of electricity.

When you add up the voltage of all three phases at one time, you always equal zero because you have the same amount of positive volts with negative volts at any given time.  So, you will find that you always have a constant voltage between all three phases at any given time.

When you add up the difference betweenvoltages of all three phases at one time, you always equal zero because you have the same amount of positive volts with negative volts at any given time. So, you will find that you always have a constant voltage between all three phases at any time.

The cable that went to ground was the coalyard station power cable. Not only were there three phases of power, but for each phase there were two 500 MCM cables. That means that this circuit was good for 800 amps of power at 6,900 volts. Giving you a capacity of 5.5 Megawatts (or 5 million, 500 thousand watts) of power. These cables were so big that a typical industrial Wire cable chart doesn’t even go this high:

500 MCM cable is also known as 5/0 cable (pronounced 5 aught)

500 MCM cable is also known as 5/0 cable (pronounced 5 aught). The 445 amps for the 4/0 cable are for only 50 volts. We had 6900 volts.

In a Coal-fired power plant, you have a redundant system for everything. So, the coalyard wasn’t completely in the dark. It had just swapped over to the redundant circuit. — This always amused me. In my English and Poetry classes in College I would have points taken off for being “redundant”, but in the power plant this was necessary to keep the plant running at all times.

As I said 15 years later, when I was training operators and electricians to be certified substation switchmen, “I know this is boring, but you have to learn it…” (but that is another story).

So, to make a rather boring lecture shorter, I will skip the part about how we had a hypot from the T&D (Transmission and Distribution) department brought in so big that it had to come in a van. They attached it to the cables to find where the short to ground was located. I’ll skip the part about how it was decided to replace the faulty cables going to the coalyard 1/2 mile away. I’ll also skip the part about how Charles Foster was able to finagle the use of Stanley Elmore’s precious blue Mitsubishi mini-tractor to try to pull the cables from one manhole to the next (the first time anyone outside the garage was able to operate his most beloved tractor…..).

A tractor just like this

A tractor just like this

Oh, and I’ll skip the part about how 1000 feet of this cable cost about $10,000 and we had six cable to replace for a cost of about $320,000 just for the cable… I’ll also skip the part about how this little tractor was too small to pull the cables through the manholes from manhole to manhole up to the coalyard, so we sent in for the big guns from the T&D department to use their equipment that pulled the cables through the manholes as easy as pulling the wool over Gene Day’s eyes while playing a joke on him. (Don’t get me wrong…. I know in his heart, Gene Day really appreciated a good joke. Gene Day is one of the best men I have ever been able to call “Friend” — which I would do shortly after playing a joke on him, after I returned to consciousness).

Anyway, after this episode was all over it was decided that something needed to be done about how all the manholes from the plant to the coalyard were always full of water. You see, the manholes were easily deeper than the lake level so water naturally leaked into them. Each of them had a pump in them that was supposed to keep them dry, but somewhere along the line, in the 5 years the plant had been in operation, each manhole pump had failed at one time or other… When pumping out the first manhole, it took days, because as you pumped out that first manhole, water would run from one manhole to the other as you actually ended up pumping out all the manholes down to the point where the cables went from one manhole to the other.

So, none other than the “newbie” was appointed as the keeper of the Manhole pumps. Yep. That would be me. So, for the next few months I spent almost all my times pumping out manholes and repairing all the pumps that had been submerged in water for years. This was my first real job.

This was my real introduction to becoming a real plant electrician (You can see how I really like using the word “real”). The most common job of an electrician was to take a motor that had failed or was scheduled to be overhauled and repair it and put it back in place to continue on it’s “tour of duty”. It’s amazing how you can take a motor that has failed, and you can “rebuild” it and put it back in operation. — This has come in handy at home as the cooling fan motor on the air conditioner unit on your house goes out every few years. I have yet to call an air conditioner man to my current house where I have lived for 11 1/2 years.

I remember that Charles Foster had told me that “paperwork” was very important when it came to motors. A history had to be kept. Certain steps had to be performed before, during and after repairing a motor. It had to be meggared properly (see the post from last week to learn more about meggars: Rivers and a Rose of the Power Plant Palace).

So, I asked Ben Davis if he could show me what I needed to do to fix a motor. His immediate indignant response was, “What? You don’t know how to fix a motor?” My response was, “No, I don’t know. Would you show me?” Ben, who up to that point had presented himself with displeasure at my presence in the shop, suddenly smiled and said, “Sure! Let me show you what you need to do!”

Ben showed me all the steps you go through to repair and “document” a motor repair in great detail. I was glad that I had found that Ben was just putting on a front of disgust at my presence in the Electric shop only to show me at the “proper” time that I had been “misjudging” him as being a grumpy person when he wasn’t really….

I had figured, before this time, that Ben really had a kind heart because I figured that if Diane Lucas and Andy Tubbs, who I both admired greatly considered Ben as a good friend, then he must really be a good guy underneath, even though he was keeping this hidden from me.

I knew the moment he smiled at my response when I told him I really didn’t know anything, that Ben had a kind heart. He couldn’t hide it any longer. If I had asked the same thing to OD McGaha, one of the other B Foremen in the shop, for instance, he would have told me to go to hell. But not Ben.

I have more to tell you about Ben, but I’ll save that for a later post. For now, I’ll just say that though Ben may not have known it during the time I spent as an electrician, he has always been close to my heart. I have always had Ben and his family in my daily prayers from the day that he smiled at me and explained to me how to repair a motor.

So, how does a lone newbie electrician pull a 500 pound lid off of a manhole by himself? Well. He uses a Manhole cover puller of course.

A Manhole cover puller

A Manhole cover puller

Ok. Our manhole cover puller wasn’t blue like this, but it had a similar shape. With a simple tool like this a 500 pound manhole cover could be popped out of the hole and dragged away. So, I used this tool as my one man crew (myself) went from manhole to manhole, where I pumped each out and lowered a ladder into each hole and disconnecting the drenched motor and brought it back to the shop where I dried it out (using the hot box in the shop that doubled as a heater for lunches), and repaired it and re-installed it.

We had all the manholes in the plant identified. I painted the numbers on each lid with orange paint. It was while I was working in the manholes 15 feet below ground that I appreciated the round manhole. I knew that as long as that manhole cover was round, it couldn’t accidentally be knocked into the hole only to crush me to death below.

Other things were of concern in the manholes where I worked… For instance, many of these holes had been underwater for at least a couple of years, and the entire manhole was covered with a kind of slime. there were also high voltage cables that had splices in some of the manholes, and I remember Gene Roget telling me that he had seen sparks flying off of some of them when they were hipoting the cables looking for the ground. The dank smell of the manholes made you think that there were probably some kind of “swamp gases” in there.

Nevertheless, when I grew weary of dragging the heavy shellacked wooden ladder from hole to hole, I devised a way to climb down into the manholes using the drain pipe from the motor. This was before OSHA had implemented all the confined spaces rules in 1994 that would have prevented me from entering a manhole alone. I was improvising and taking a risk of falling and hurting myself each time I entered a manhole.

I ran into one of the reasons for not leaving a person in a manhole alone one time when I was working in a manhole near the intake house and another crew drove up and parked their truck near the hole I was working in. I remember that while I was working there, I suddenly became nauseous. Not sure why, I climbed out of the hole.

The truck that had been left idling nearby had been emitting toxic fumes that had looked for the lowest place they could settle, and that happened to be in the manhole where I was working. After that, I always kept an ear out for any motor vehicles nearby when I was in a manhole.

Ten years later, in 1994, OHSA added some new laws to the books that made it mandatory to have a “hole watch” stand outside a hole watching you while you worked in a manhole. You even had to have a safety harness tied to a safety hoist so that if you passed out while in a manhole the hole watch could pull you out without having to enter the hole.

This is a special hoist designed to lift a person out of a confined space without seriously injuring someone that is caught on obstacles.

This is a special hoist designed to lift a person out of a confined space without seriously injuring someone that is caught on obstacles.

Needless to say. I got my feet wet as an electrician popping in and out of manholes like the gopher in the arcade that you try to bop on the head.

One interesting story that happened during this time happened when Blake Tucker, who had been a summer help with me in the garage, and then later became a summer help in the electric shop, was sitting with me while we were going to fix a pump in manhole 215 (I believe this is the number of the manhole next to the intake where the fly ash pipes go over the intake).

The hole was full of water, and the pump had naturally tripped the breaker….. For some reason I decided to go into the intake switchgear and reset the 120 volt breaker to the pump in the Distribution Panel. When I did. I returned to the hole where Blake was waiting for me. I reached down into the hole with my foot and I kicked the drain pipe that rose from the pump and made a 90 degree turn up close to the entrance.

When I kicked the pipe, the motor actually began running. We could see it 15 feet below us in the clear water running. It was an open face motor, meaning that it wasn’t sealed and made to be a submersible pump, yet it was running under water. A year later we decided that it made more sense to replace all the open motors with submersible pumps.

vertical pump with an open motor on top

vertical pump with an open motor on top

Submersible Pump made to sit in the water without the water leaking into the motor.  -- That's the idea anyway.

Blake Tucker and I watched for 1/2 hour as the pump sucked out the water from the manhole. When the level of the water reached the top of the motor, the outboard fan that had been slowly rotating all of the sudden kicked into high gear and we could see that the pump had been running at full speed all along.

This fascinated me. I figured the water must have been pure enough not to be too conductive (pure water is a natural insulator…. oddly enough). We could easily see this pump through 15 feet of water, so it must have been pretty clean. That was the only time I have ever seen an open motor happily running submersed in water… It is not something you see every day….. for instance…. It is not every day that you see a janitor with a Psychology major acting like an electrician sitting beside a manhole staring down into the darkness in a power plant either. But there you are…

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2 responses

  1. I never would of considered a round man holes important role .. But of course it is so logical after you point out the reasons why.
    Thanks for sharing. Interesting facts

    Liked by 1 person

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