Water Well Journal

February 2015

Water Well Journal

Issue link: https://read.dmtmag.com/i/451364

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Page 45 of 75

O ver the past five installments of The Water Works we have con- centrated on the use of water wells as sources for an engineered (larger) water system. Included in this discussion have been a treatise on basic geology and rock types, hydrogeological terms and defini- tions, the different types of water well drilling machines and their characteris- tics, the principles behind siting a new well location, and the various methods of well construction available in today's world. In this sixth insert we will introduce a guideline on selecting the optimum size (diameter) for a new well based on the needed flow rate, sizing a pump for an existing well, and typical sub- mersible and vertical turbine motor data. Well Sizing Criteria— Table 1 The information contained in Table 1 is reflective of two basic criteria for well and pump sizing in a new or existing well. In order to be accurate, usable, and relevant to all the regions of the United States and many non-U.S. markets, I de- veloped this table, including verification of the current manufacturers of vertical turbine and submersible well pumps and submersible and vertical turbine pump motors. I was able to locate and refer- ence 12 current and nationally available manufacturers of vertical turbine or larger submersible well pumps, 9 larger submersible pump motor manufacturers or suppliers, and 10 vertical holloshaft or solid-shaft electric motor manufactur- ers or suppliers. Although I'm fairly confident I've included data on the vast majority of larger pump or motor models offered by most of the currently operating well pump and motor manufacturers, there may be a few exclusions and even over- sights of some specific manufacturers, models, or applications. In other words, even though a specific duty or design condition may be shown in Table 1, there may not necessarily be a pump or motor available for your specific appli- cation in your specific market area. It is therefore up to each user to de- termine the completeness of the infor- mation shown in Tables 1, 2, and 3 for their market and operating region. In ad- dition, since some manufacturers offer a limited or possibly no selection of a certain bowl diameter, pump type, or speed, during the compilation of these tables I required that no less than four pump or three motor manufacturers must offer a pump with the stated nomi- nal diameter, BEP flow range, and rota- tional speed for pumps or horsepower, speed, frame, and type (submersible, vertical holloshaft, or solid shaft) for motors. This selection basis helps to en- sure there is no individual manufacturer bias and that a designer should be able to find and evaluate at least two or three selection alternatives in every part of the country. To assist with navigation of Table 1, the following is an overview of the indi- vidual columns. Columns one through six are marked in parentheses near the top of each individual column as follows. (1) Nominal Bowl Diameter Starting at a 2-inch pump shell diam- eter and up through 19-inch/20-inch to 30-inch bowl diameters, this column references the majority of the available pump bowl or outer pump casing nomi- nal, not the actual, diameters. (2) Operating Pump Speed and Pump Types This column is used to determine the nominal rotational speed (in RPM) of the various types of pumps so listed. VSP is an acronym used for a vertical submersible pump, while VTP is used to describe a vertical turbine pump. (3) Typical BEP Zone Flow Range Classified here is the best efficiency point (BEP) zone of the average BEP for a given bowl diameter at a given speed from all manufacturers. The BEP zone, as opposed to the BEP alone, was developed to indicate a +/– 10% range of flow up or down from the average best efficiency point as not all applica- tions are designed to operate at a single fixed flow rate. This helps to provide a margin of flexibility in the design and pump selec- tion. For example, a 6-inch nominal di- ameter bowl for a vertical submersible well pump (VSP) with a 3500 RPM rotational speed shows a 50-500 GPM BEP flow range. This means the lowest average flow for this diameter and speed of pump is intended as 45 GPM (50 GPM × .90, or minus 10%), while the highest average flow rate is intended to be 550 GPM (500 GPM BEP × 1.10, or plus 10%). (4) Minimum Well Casing/ Liner Diameter This is for selecting a well pump for an existing well or retrofit installation. The left side of the column shows the minimum diameter of well casing or liner for each pump type, nominal diam- eter, and speed along with the riser pipe (R) size range for submersible installa- tions or the column size (C) range for ED BUTTS, PE, CPI THE WATER WORKS ENGINEERING OF WATER SYSTEMS Part 11(f)—The Source: The Well, Part 6 44 February 2015 WWJ waterwelljournal.com

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