So, I was at university, this power plant was located about 10 or 15 miles south of where I lived, and I got a summer job there one summer, and we really didn't do very much. I think it was all about hoping after we graduated that we would come back and work at the power plant. So, I got to learn all about how power plants work. It turns out that I know people that work there now, and was able to get the following data for this segment of the lecture. So, this is the JH Campbell Plant in Michigan. It is right on Lake Michigan, so, in the state of Michigan. People in Michigan, they use their hands. Where are you from? From Michigan, and they put their hand up because it's got that thumb thing that sticks out. So, it is on the west coast, Michigan is here and Chicago's down here. So, I went to Google Maps, took an overhead of this. Actually, I wanted to say one more thing, let me back up. So, you see there's two smokestacks here, exhaust gas stacks. There is two boilers and turbans inside this building, and they call this unit one and unit two. This is the one where I worked at. This is unit three, and at time it was the largest single boiler unit in the country. I don't know if that's still true, but it was when I worked there. This device right there is a conveyor system that takes coal that we'll see in the overhead, that is out in this field over here, and it gets shipped from units one and two, and gets shipped over to unit three to be burned and make steam and turn a turbine that turns a generator that produces electricity. So, here is the overhead. So, coal comes in, I think there is actually some train coal cars right there. So, this is the train track. Has anyone seen them here, going up to the high country or coming down from the high country? Because they mine coal in the western north here and then comes down through the Denver area if any of you have been up highway 72, and seen the coal trains, going by. They are really long and full of all this coal. Those coal trains come in, and they come into this building and as I understand it, and the way it was explained to me is there is this big claw-like hand, that grabs a hold of each car, and tips it over and all the coal dumps out into this underground hopper that is three or four or five, six stories down below the surface. Then there is this conveyor belt that transports all the coal up to this central distribution hub, and they bring it out, and they separate it out here into various grades, various qualities. They get coal from the west. It has a certain set of properties. If they get coal from Tennessee or the east, that has different set of properties. Then later, they use bulldozers to bulldoze it up, and it gets converted up, and conveyed into units one and two which are here. You can see that, that's the smoke stack right there for units one and two. Then that bridge that I showed you in the previous picture, this is a conveyor system that takes the coal over to unit three. That's how the coal gets into the buildings. So, unit three is 830 megawatt and it has over 15,000 hardwired IO points that they're monitoring. Forty three, forty six are analog and 10,940 are digital sensors that they are monitoring. So, I got 15,000 points that they are keeping an eye on. Site operators, the engineers, the operators, the maintenance, my niece's husband is an operator. He works at that plant, and he was helpful in getting some of this information. They are constantly reviewing all these trend data, they are looking for alarms, they're looking for certain values that they call point excursions that go above a certain level, something is about to go wrong or is going wrong, to diagnose past failures and to anticipate future failures. So, that coal comes into the plant by those conveyor systems, and this is a coal pulverizer. The coal is fed in and falls down, they're lumps like the size of a softball, maybe a little bit smaller, maybe marbles up to like softball size, hangs at this at this point. The coal is fed down into where the rollers are, and that's what they really look like in real life. Those have been used for a while. There is a shaft that is driven by a motor that comes right down the middle and makes those rollers roll around in that track and it pulverizes the coal into a very, very, very fine powder, okay? That powder then is forced with forced air out tubes that lead up into the boiler, where there is basically a controlled explosion going, when I worked there college students. So, it is a good thing the boilers are run at negative pressure, okay. So, there is all these service hatches, and the boilers, many, many stories high. We're engineers and we're curious. Hey, let's go over and open that access hatch and look inside. Crank the handle, open it up and it's like looking at the sun. Wow. Close it and you can hear all this air being sucked in and we never got in trouble for that. We were just curious. So, I don't know what the rotational speed of these wheels are, but they are really loud at the unit three, so the boilers sits right in the middle of that big building. There were four on the main floor sitting on concrete, four on one side, and four on the other side of the boiler, and pretty much all eight of those were running constantly. Pulverizing coal and blowing that coal up into the boiler to be burned. There is a link to a YouTube video, if you want to find out more about coal pulverizers. So they had a problem with a main shaft vibration and that main shaft breaking. Yes? If you go back to the other slide looking at the pulverizers, what kind of yield do you get out of that? With eight of those, how much earnable coal do you get per hour? I have no idea. Don't take this specific question but I'm trying to get an idea of how long it actually takes pulverize a chunk of coal, is it something that's really quick? It just like drops in. This is my understanding. Coal is constantly being dropped in there and is being pulverized. When the particles get down small enough, they get caught by the forced air and they're able to get up into the pipes that lead to the burner and if they're too big still, they fall back down and they get smashed. So it's sort of like hail in reverse. It goes around and around and eventually the hail falls to the the ground. So the particles keep getting smaller and smaller and smaller until they can escape. One of the things I had to do when I was there, one of the jobs they gave me, was to map all the pipes from the pulverizers up to the sides of the boilers because they had leaks. You'd come in every morning and there'd be coal dust all over on the main floor. They were trying to figure out where the leaks were coming from, so they had me draw this isometric drawing of where all the flanges were. Then after they had that, they were going to send technicians out and check all of those flanges to see if the bolts had to be tightened down on them because they were losing a certain amount of coal dust. They were trying to improve efficiency and reduce waste. That was one of the jobs that they gave me when I was working there but mostly we sat around and talked and played cards. So to the main shaft vibration problem. So they had issues with the main shafts breaking and this was in Unit two, due to various issues, a change in the fuel blend mix. They switched from 100% Eastern coal to 100% Western coal. Coal comes with some impurities. When they mine it, it has some iron in it which can't be pulverized so you get a little hunk of iron in there and those huge wheels are rolling over the top of a piece of iron, it's introducing some vibration. Sometimes running the mill too lean, the pulverizer too lean, which means there wasn't enough coal getting in there during startup and shutdown etc. So in an attempt to remove the mill from service prior to failure, they installed vibration probes on the middle housing right on the outside. They set up alarm limits and Alarm Response Protocol to remove the mill from service if the overall vibration goes above a certain prescribed set threshold, a limit. In the example below, the 2A Mill went above 27.5 mils on 11/15 at approximately midnight and the operators removed the mill from service and we ended up finding tramp iron in this case, foreign metal from the mine in the mill. The Alarm Response Protocol directs the operator to the trend, so I'm sure some light on a screen or something starts flashing to alert the operator. They see that when it hits Alarm Limit one and then they remove the service if the vibration continues and they hit High Alarm Limit two for two minutes they take the mill offline. Then it has to go below 14 mils of vibration for 32 seconds in order for it to reset. So that was a protocol that they came up with. So they sent me this great graph. So the blue line is mill's running, and it's digital and then they shut the mill off here so the mill's not running. So you can see the vibrations here, this is the Alarm Limit one at 22 mils of vibration and here's the second at 27.5 mils of vibration. So they're tooling along, it's two O'clock, three O'clock, four O'clock, everything's great. Then we're about 9:30 or so, we get to this little spike here but it's not high enough to trip it. Then all of a sudden coming up right about 11 O'clock, a bunch of tramp iron must've gotten put into the mill. It started to get all of this vibration and it crossed the 22.0 mil mark and that drew the operator's attention to this, we have to watch this. Then it crossed the 27.5 mil mark and you can see that the operator shut that mill off and avoided breaking the main shaft. It was very expensive for them, they've probably got a couple of spare shafts laying around. Have to tear the whole mill apart, reinstall that broken shaft. Big deal. Very expensive. So it's just a table of what their normal operating range was was four to 11 mils. The Limit one was 22 and two is 27.5 and the reset periods. So they have a little historesis built into that 14 mils for 32 seconds. Any questions about that? Yes? When they shut it off, do they just try and clean out any iron residue? I would imagine, yeah. There's probably some service access hatch on it when it's shut down and service technician goes in there and cleans all that, cleans it all out then they start it up again. Get that tramp iron out of there. Are there any pulverizers that have built-in electromagnets or something, where it can try and pull the iron out? That is a good idea, actually. I don't know. You'd have to time it right to have it get pulled out between the gaps or if the thing is just moving too quick that they can't escape, or maybe you could shut. You could have magnets, some kind of magnets on the way in maybe. You wouldn't want to pull it out after it's been in there. I think if you were going to try to use magnetics to pull iron out, you'd want to do it before the coal actually got in the pulverizer. I thought it was like the coal is like 1% iron and it accumulates during the pulverizing process but you were saying there was actually chunks of iron. That's my understanding, chunks of iron. John Hiddema and I, we had this email exchange and it sounded like it was chunks of iron, and it wasn't like small pieces of iron were building up. Yes? There's a company at my home town, how they have tackled this is they have a conveyor belt that's electromagnetic in nature. So when the coal comes in and it's getting shipped, the ones that have tramp iron in them, they kind of stick to the belt and then they end up in a different stack as compared to the rest of the stack. Yeah. That's a good idea. This place needs to do that. I'm surprised they haven't done that if that technology exists. Yeah, I'll have to ask him. When I talk to him the next time I'll ask them why they don't have that, magnets pulling that tramp iron out of there. It could be implemented at the place where you have the hopper. Yeah, exactly, yeah. Yeah. Anywhere along that path. Yes. It could take the iron out of there.
