Water Well Journal
Issue link: https://read.dmtmag.com/i/767379
Final Pump Selection Once the preliminary design and cost estimate has been submitted to the client and accepted, the next design step in- volves final selection of the pump and motor. Where a VTP is somewhat a unit comprised of many pieces of various types of different equipment assembled and installed together at the site to create a single pumping unit, a submersible pump is largely comprised of the pump and motor often assembled into a single unit at an offsite factory or manufacturer's facil- ity and shipped to the site for installation. The selection of the submersible pump and motor must be performed so the final product is a cohesive unit, designed and intended to operate together as a single pumping machine. Based on the preliminary design, an intimate knowledge of the system, pump, and motor parameters and limitations are usually well understood by this stage. The steps in Table 1 comprise a selection outline and each step is generally indicated and examined during the prelimi- nary or final submersible pump selection. Not all the steps will apply to every installation, but each one is nonetheless important to a successful and long-lasting submersible pump installation and each should be considered. Although the pump's hydraulic and mechanical design is obviously important, the primary factors to a successful and long-lasting submersible pump installation usually rest on two individual—but equally important—factors. (#1) The installation and placement of the pump to ensure there is always adequate submergence over the inlet (pump suction) to prevent cavitation or vortex conditions as well as the proper location of the motor within the well in order to be sure adequate water velocity and volume passes over the motor or an alternate method of motor cooling will occur to protect the motor at all flow rates. (#2) A full evaluation of the current or proposed electrical installation to verify there is or will be adequate starting and running voltage available, along with a full and balanced three-phase power supply from the utility (where applicable) or generator, and the use of proper motor controls, including (at a minimum) short circuit, overload, and phase loss and reversal protection, and low water level protection. I cannot stress enough the relative success of a submersible pump and motor installation is heavily vested in the designer's careful and diligent procedures in each of the steps in Table 1 —not only to ensure a satisfied customer, but to provide a degree of self-satisfaction. We will review each step in sequential order in the next two installments. Until then, keep them pumping! Ed Butts, PE, CPI, is the chief engineer at 4B Engineering & Consulting, Salem, Oregon. He has more than 40 years of experience in the water well business, specializing in engineering and business management. He can be reached at epbpe@juno.com. WATER WORKS from page 35 WWJ waterwelljournal.com 36 January 2017 WWJ