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Terms Part 2 by Bill Corey Pentair Water Training Institute Let’s start this month with the term: Force - The applied effort attempt- ing to move something. If I put my shoul- der into the wall, will I move it? Probably not, BUT give me a bulldozer and I’ll knock the house down. Pressure - The effect produced by the application of force over the surface of an enclosed area. If the area is not contained, it would be difficult to get a pressure reading on the force closing down. Atmospheric Pressure - It means the weight of the atmosphere at a given point at a given time. The atmosphere is made of two components: air and water vapor. At the equator, the atmosphere is said to reach up 360 miles. Of course, the higher you go, the thinner the atmos- phere gets. Whereas, the closer you get to sea level the heaver it is. More mol- ecules, more weight; less molecules, less weight. If we were to give an astronaut a pressure gauge and say, “When you get in deep space, set this gauge to zero.” When he gets back to earth at Cape Kennedy and gives us the gauge back, it would read 14.7 psi. That is the average weight of the atmosphere at sea level, air and water vapor. Some want to think when water turns to vapor it goes back to its base components of hydrogen and oxygen. That is not the case. I ask my students where clouds come from. The answer is very obvious - the water vapor pulled up in the atmos- phere. Vacuum - We don’t mean the per- fect vacuum of outer space, but some- thing less than atmospheric pressure. Pressure moves from high to low, so if we make a low enough pressure at the eye of the impeller, the weight of the atmosphere will push the water up to us. We call this suction, but in reality we are really creating a lower pressure than the atmosphere, causing the atmos- phere to push water up to us. PSIA - Pounds Per Square Inch Absolute; a gauge which reads PSIA includes the pressure of the atmosphere at that time. Remember, pressure will change throughout the day and this gauge has the ability to read it. PSIG - Pounds Per Square Inch Gauge; this type of gauge reads zero if it is not attached, to something. When it is attached you are reading the pres- sure over the atmospheric pressure, but not including the atmosphere. Next month we’ll see what cavita- tion means. Bill Bill Corey may be contacted via e-mail at admin@ worldwidedrillingresource.com 61 WorldWide Drilling Resource ® FEBRUARY 2014