WorldWide Drilling Resource

Terms Part 7 by Bill Corey Pentair Water Training Institute Cavitation damage in a pipe - there should be no doubt this can happen. We have seen examples in previous articles. Whether in a pump or a pipe, if we lower the pressure over the water to the vapor pressure point of the water, it will convert at any temperature. It is the speed (velocity) of the water in the pump or pipe that causes the lower pressure. So, if we control the speed, we control cavitation. But speed is not the only thing we need to control. I did a presentation for the Wisconsin Department of Natural Resources and, as I was leaving, someone called my name and asked if we could talk. I of course said yes. He told me he ran a heating com- pany and they had a problem at one of the athletic clubs in Milwaukee. They were using hot water to heat the build- ing and every once in a while the ½- inch copper pipe of the heating bundle would pop a hole in it. Could this be cavitation and, if so, what could be done to prevent it? I asked what the temperature of the water was, and he said between 160°F (71ºC) and 200°F (93ºC). When I asked for information about the flow, he did not know so he could not help me. He did tell me the damage was always on the outside of the curve in the bundle. Yes, I’m sure it is cavitation. Remember, the temperature is another way to create cavitation. I suggested he keep the tem- perature of the water to the 160°F (71ºC) area and see if he was still having the problem. When we use the word cavitation , we are really talking about bringing the water to a boil or flash point. I was once told I could not say that because peo- ple just wouldn’t understand the fact. I told the engineer to let me tell them because he was an engineer and just couldn’t talk to everyday people. I hope I have gotten my point across so it does not have to happen; and when it does, it is just a mistake which can be cor- rected. There are those who would rather not, and to them, all I can say is, thank you, because they will continue to purchase parts they should not have to because they do not want to change their system. Next month, we’ll talk about flow rate. Bill Bill Corey may be contacted via e-mail at admin@ worldwidedrillingresource.com Look for Frequently-Used Geological Terms next month! 67 WorldWide Drilling Resource ® JULY 2014