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Terms Part 9 by Bill Corey Pentair Water Training Institute Fittings are the parts of a system that make the water change direction in some way. This could be an elbow, a reducer or expander, a tee - something that takes you away from straight pipe or changes the size of the pipe you are using. As with most things in life, there is a cost. Remember, when water is moving through a pipe, there is weight and pressure pushing it which gives it momentum. As it streams along on the inside of the pipe, there is friction be- cause of the contact with the pipe walls. BUT that’s not all. When the water gets to an elbow, it wants to go in a straight line; the elbow, of course, has other thoughts and makes it turn. However, in doing so, we find a lowering of pres- sure on the outside of the elbow be- cause of an increase in velocity. of course, the inside of the elbow has a slightly higher pressure because it has less water going around it. It looks like this: As you can imagine, there will be some losses in this elbow also. However, these losses are not calculated the same as if it were straight pipe. With straight pipe, you either use the Darcy-Weisbach tables or the Hazen-Williams tables. The first uses clean new pipe only, and mul- tiplies the pipe length times a friction factor for smoothness of the pipe, which gives you a loss of head in feet. Hazen- Williams states that every 100 feet of pipe will have the same loss; so when using their multiplier, you would simply take your total length of pipe and divide it by 100, then multiply that by your fac- tor. oh, it might be useful to know they also feel that as pipe gets older, it cakes up on the inside, and that will add more friction because it will increase the veloc- ity of the water. All of this is fine if all we have is straight pipe. But when calcu- lating fittings, you’ll find we use some- thing called the “K” factor method to calculate, not the head loss, but the conversion of the fitting into a straight piece of pipe. Then we add those all together to get what we call an equiva- lent length of pipe. Add that to your actual length of pipe and you now have an effective length of pipe to go to the tables with. Next month, let’s take a look at a man named Bernoulli. Bill Bill Corey may be contacted via e-mail at admin@ worldwidedrillingresource.com 69 WorldWide Drilling Resource ® SEPTEMBER 2014