| You’ve probably heard the saying, “asleep at the switch.” It’s usually associated with some sort of disaster, found later to have been caused by human error. Someone wasn’t paying attention, and something very bad happened. The meltdown of the Soviet nuclear power plant Chernobyl in 1986 comes to mind. You may be surprised to learn that the saying has its origins in the world of industrial controls, or more specifically, manual controls, as we’ll see in this article.
Last week when we opened our discussion on manual controls, we talked about how they work just as their name implies, that is, someone must manually press a button or throw a switch in order to initiate a factory operation. In other words, a manual control requires human intervention to initiate an action, such as pushing the start button. The machine will then continue to run until a person hits the stop button. Let’s go now on a virtual field trip into a telephone factory to see how a basic manual control system works. It has a conveyor belt operated by an electric motor, and this motor is connected by wires and a power switch to a 120 volt power source of alternating current. Figure 1 illustrates what we mean. It shows that when the power switch is in the open position, a physical air gap exists within the electrical circuit. This prevents electricity from flowing through the wire because electricity can’t jump over gaps.
Figure 1 – Open Power Switch Enter a human into the scenario, someone who grabs the power switch handle and manually closes it, eliminating the air gap. See Figure 2.
Figure 2 – Closed Power Switch When the power switch is closed, a metal conductor bridges the gap, causing electricity to flow through the metal conductor to the electric motor in the circuit. This brings life to the conveyor belt. As long as the power switch remains closed, the conveyor belt will continue to operate. That’s it, that’s a basic manual control system. It’s simple to operate, but it does have one major flaw. It requires constant monitoring by a human. Aside from opening and closing a power switch, humans are required to monitor operations, in case something goes wrong. The operator watching over an industrial machine performs the same function as the pilot on a plane, that is, to start-stop operations, and to intervene in case of an emergency. Computers fly modern jets. Pilots serve as trouble shooters when the unanticipated disaster situation occurs, because computers can’t yet creatively problem solve. Next time we’ll introduce the element of an automatic control system, which will virtually eliminate the need for human intervention and with it human error. ____________________________________________ |
Posts Tagged ‘production line’
Food Manufacturing Challenges
Sunday, September 18th, 2011| Some people just have a knack in the kitchen, and my wife is among them. She transforms raw ingredients into the most amazing culinary delights, almost like she’s waving a magic wand. The finished products are works of art, hand crafted with tender loving care, and lucky me, I get to feast on them regularly!
During the course of my engineering career I’ve been employed within many industries, and at one point I made the decision to leave the electric utility industry and enter into the world of food manufacturing. I accepted the position of Plant Engineer with a wholesale manufacturer of baking ingredients and frozen pastry products. My main responsibility was the design of food manufacturing equipment and their production lines. What I had expected to be a relatively straightforward process soon proved to be more challenging. I was no longer working with hard metal as my raw material, that is, gears, nuts, and bolts, but a whole new arena of things described by adjectives such as gooey and pastey. Engineers don’t typically create food products, and let’s face it, you probably wouldn’t want to eat anything that I cooked anyway! But an engineer working within a food manufacturing plant must act as a liaison between the worlds of engineering design and the culinary arts. Now food manufacturers typically hire professional chefs to develop new products in their research and development (R&D) kitchens. Like my wife, they’re well qualified to produce wonderful hand-made culinary delights. The sticky part comes in when their small batch recipes and preparation techniques don’t translate smoothly to the world of mass production. When it comes to handling food, human fingers are far superior to metal machinery, and raw ingredients behave differently for each. Herein lies much of the challenge for design engineers within the food industry. How do you design equipment and production lines to make huge quantities of food that look and taste as good as the prototype products made by hand in the R&D kitchen? Next week we’ll find out. ____________________________________________
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