Sometimes equipment does not work the way you expect it to. Sometimes you follow all the instructions, you set up a machine in a way it is supposed to or has worked many times, and you get – something else. You get a problem, unexpected results, something weird.
Perhaps influenced by the title of a 1981 album by the rock group The Police, I think of these problems as Ghost in the Machine problems. WWII pilots used to imagine that there were little Gremlins in the planes, causing mischief and messing with the equipment. Sometimes I feel like a piece of equipment has suddenly become possessed.
I’ve come to love these problems, only because they are exciting to solve and they are interesting to pick apart. Don’t get me wrong, I’m talking about it like it’s fun, but it is almost never fun for the operators. How often do you have equipment break down and you feel like you have all the time in the world to address the issue? That’s not the way it works. When equipment breaks or malfunctions, you often have the entire management lineup looking over your shoulder and sometimes the entire process ground to a halt while some weak link in the production chain suddenly becomes the Achilles heel of the operation.
I’m not always talking about things that break. If something breaks, it’s obvious. You have to tear it apart, fix it, and put it back to work. The really maddening ones are the ones that look OK, but aren’t doing what they are supposed to.
Years ago, I was selling round screeners. They have a system of weights that adjust the vertical and horizontal intensity of the vibration, as well as an adjustment that changes the way the material flows on the surface. They came up with this great new system where the weights were no longer bolted down, but were slotted so you could quickly make adjustments. The problem was that when the machine was turned on, the weights vibrated loose and migrated to a balanced position. The problem is that vibratory screeners are deliberately in an unbalanced position. We had just set it up and when it didn’t work right, when the product didn’t flow across the screen and out the discharge, we were confused. Then we noticed that the weights had migrated and employed a 60 cent zip tie to correct the problem. Another time, we determined that the platform that the unit was mounted on could sway. It would sway in a dampening resonance so that the base was moving back and forth under the screener, which was actually stationary. It was about 7′ off the floor and every time I climbed up the structure to look into the screener to see what was happening, my weight would stabilize the base and make it work again. As soon as I stepped off, it would stop working again. It was almost comical. Physicists always say that the act of measuring or observing a phenomenon changes it, but this was an example where that was literally true. We threw three 80 pound sacks of flour over the cross braces and the machine worked perfectly, giving them time to redesign the base so it wouldn’t shake.
I always tell people that intermittent problems are the most difficult to solve. We had one screener that had an ultrasonic vibrator on it. Those are used when the powders are so fine that they float over the top of the screen instead of sitting down and going through the screen holes. You turn on the ultrasonics and it’s like magic, the powder goes from dancing and jumping on top to vanishing through the screen in an instant. I went out to watch it with the operators and noticed that sometimes it worked great and other times it did not. It took a while, but we finally figured out what the problem was. The ultrasonic control unit was like a little computer. It has all these printed circuit boards inside of it. It was bolted to a steel column next to the separators. The column was sitting right below a huge conveyor on the next floor up that shook the floor and the column that the control panel was mounted to. I noticed when I had the panel open and had my hands against the board, that the separator worked. When I removed my hands, the separator stopped working. We determined that there was a circuit board with a hairline crack in it. When the panel vibrated, the crack in the circuit board opened up and the connections were broken. When the unit was not shaking, it would come together and work fine. We replaced the circuit board and remounted the panel to a base that did not vibrate. Problem solved. It only took about 3 hours of scratching our heads and staring at the system before the ghost came out of the machine.
The worst problem is when someone has bad information and they are convincing. Twice, I’ve identified electrical problems over the phone and then spent hours on site until finally getting back to where I started. Once, an automotive plant installed a new mixer on a water treatment tank. It was only running at about 30 rpm when it was rated for 350 rpm. The Maintenance Manager called me up, furious. This was a new piece of equipment and didn’t work right! What kind of crappy equipment did I sell him? I asked if he confirmed that the voltage and amperage supplied to the mixer was correct. “What do you think, I’m a moron?! Of course it’s correct!” OK, OK, let me look over the system, which I did for about 3 hours. Tired, and with sweat dripping off my forehead, I asked if he would please check the line current, because I checked everything and it all looked fine. 20 minutes later, the electrician arrived, flipped open the panel, and clipped the meter to the lines. “This bus is bad. It’s only putting out 25 volts. I’ll replace it.” If I remember correctly, I did not get an apology from the Maintenance Manager, but at least I had the satisfaction of nailing the problem. I just wished I had been more insistent. About 8 years later, something very similar happened with another plant. I had an inline sifter installed, an exact duplicate of a model I had designed and sold 2 years earlier. This time, there was a consulting engineer involved. During startup, he called me and was quite angry. My equipment was making a terrible noise. “Is the rotation correct? Counterclockwise when viewed from above?” I got the same kind of response, the engineer was indignant that I would insult his intelligence by asking such a novice level question. I spent an hour looking at the equipment, which was howling like a banshee. I figured it was misaligned and had to listen to the engineer tell me about his idea of how the entire machine was poorly designed and needed all the internal tolerances re-machined. I took a video of the sifter spinning, more to give the sound than the visuals. I sent it to the designer and asked if he could explain what was going on. About a minute later, he wrote back “It’s going in the wrong direction.” I was so convinced by the engineer that this had been checked that I stared at it for an hour and never even questioned it. We reversed the motor leads and started it up and it hummed along perfectly.
There is always an explanation of why a mechanical piece of equipment behaves the way it does. You just have to understand how it’s supposed to work and then observe for a while. Seeing inside the equipment would be perfect, but is often impossible. I carry a stethoscope and a temperature gun, which helps you listen inside the equipment and understand where it is overheating. It’s amazing how much you learn by listening to the equipment or putting a hand on it and feeling the vibrations coming off of it. The guy that stands next to the machine and operates it on a day to day basis is your best source of information. What has changed? Did it used to be working fine and then started working poorly? Does the operator remember what happened about that time? The clues are almost always there.
Process equipment rarely operates in isolation. It is usually part of a system, interacts with a process liquid or powder, and is supported by some kind of structure. Those system components become an extension of the equipment. Systems and processes operate in feedback with equipment, so you have to consider what feedback they are imparting on the equipment. When a piece of equipment fails, the broken parts can often yield clues. I remember looking at a conveyor and seeing the distinct impression of the threads of a bolt that was dropped into it. While it is never fun to have to deal with a broken piece of equipment, it’s always helpful to understand exactly what happened. This is the best way to prevent it in the future.