Water Well Journal

July 2015

Water Well Journal

Issue link: http://read.dmtmag.com/i/529509

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Page 55 of 83

T he Water Works column is always dedicated to the engineering of water systems and the many aspects that go into that task. For many of you, the content may seem old hat at times, but for some oth- ers I bet the information contained here will be new to you and even somewhat interesting. Over time, too many of us have be- come lax about the procedure of select- ing and designing a pumping system. This includes me. You might muse to yourself, "I have done this a thousand times and every single one has worked okay." It's pretty easy to adopt that kind of an attitude when you are so well entrenched in your business. But have one disaster—and I don't mean a case where your crew forgets a pipe wrench. I really mean a four alarm fire kind of disaster—and I bet your next big job of selecting a well pump won't go so easy on you. So let's start this installment by as- suming you already have a well drilled and ready for a pump to be placed in it. Pumping Basics There are two basic tasks I always do before getting down to design the actual pumping system. The first is to ask the client if he or she has a preference for a submersible or a vertical turbine pump. I do this even if I know them. You might be surprised at how often that simple question catches people off guard. I have always found it, though, a way to break the ice and open up a more formal line of questions. You might also be surprised at how many say things like, "I wouldn't have one of those submersibles in my new well. I want to see what I paid for on top of the ground." But just as often a customer might respond with, "Do you think I'm made of money? Of course I want the sub- mersible; it's half the price." Well, if nothing else, the entertain- ment makes it worthwhile. These types of responses seem to come back to me regardless if the cus- tomer happens to be a farmer, a public works director, or a plant supervisor. Yet I suppose just as many people will ask me the loaded question, "I am not really sure. What do you think I should have?" This is always a tough one and you really can't win. But it is an important question and one that needs answering. As most of you know, there are places you simply cannot use a sub- mersible pump. Just as simple is the fact there are wells you don't dare install a vertical turbine pump into. Granted if my client happens to be an old customer I have known for years, I probably already know the answer; it's really just a formality to ask him. Many cities and even some farmers have a personal or professional policy they will accept only one type of well pump. Nonetheless, you still must know which one. The second task involves looking at the well log or report. Almost instantly, I can gauge if there is an issue with the well, such as top feed water or too small of a well casing, that will ultimately cause problems to me or the client if we decide to use one type of pump over the other. This is the time to face up to these kind of problems—not later after the problem you worried about has already started. In most cases, a vertical turbine pump or submersible will equally do the job and perform admirably. However, we all know the limitations of higher speed and the consequence to bearings and pump and motor life. So if the client is concerned about energy costs or prefers operating life over first cost, then this is also the time to discuss the benefits of turbine pumps over submersibles. Beyond that initial discussion, the topic will rapidly turn more to the technical side. Given the choices between the two pumps is often so critical, I will dedicate the rest of this article to a discussion on vertical turbine pumps and then turn to submersible pumps in the next install- ment. The final pump installment of this series will illustrate a design selection for both units and the methods one uses to choose one or the other. Fundamentals of Vertical Turbine Pumps Vertical turbine pumps (VTPs), often referred to as lineshaft turbine pumps, have been in use since the early part of the 20th century and coincided with the rapid development of electric motors. This type of pump belongs to the "dynamic" group of pumps, in which energy is imparted to the liquid to effect movement. The turbine pump was developed as an offshoot of an ordinary centrifugal pump and was originally intended to re- place centrifugal pumps in applications where the water surface was lower than ED BUTTS, PE, CPI THE WATER WORKS ENGINEERING OF WATER SYSTEMS Part 12—Pumping, Part 1 WATER WORKS continues on page 56 54 July 2015 WWJ waterwelljournal.com The relative capacity of an impeller mostly depends on the width, amount of vanes, and internal area of the impeller.

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