Water Well Journal
Issue link: http://read.dmtmag.com/i/573697
bles a conventional centrifugal pump and standard motor in construction. This type of pump is also designed for continuous opera- tion in a submerged environment. All the same, many sub- mersible sewage pumps, due to motor construction using oil cooling and lubrication, can also operate in an open or par- tially submerged condition. This type of operation is never permitted for a deep well type of submersible pump because of their inherent water cooling and lubrication design. Although the submersible style of pumps includes sewage and effluent pumps, for our purposes here, we will limit our discussion to the multi-stage centrifugal type of submersible pumps. However, much of the information that will be covered also applies to the sewage and effluent style of submersible pump. In fact, many of the larger diameter deep well submersible pumps use the same bowls, impellers, and other items as a comparable vertical turbine pump (VTP). Indeed, larger (≥ 6-inch diameter) submersible pumps are referred to as submersible turbine pumps due to this similarity. The basic difference between the units is the operating speed. Sub- mersibles generally operate at 3400-3600 RPM, while VTPs usually operate at 1800 RPM. Also, the driver (motor) is now located under and directly connected to the bowl assembly. The current popularity and widespread use of submersible pumps is due to the lower purchase cost, easier and cheaper installation, elimination of a long lineshaft as required by a VTP, less noise, and ability to pump higher volumes of water at higher heads from a smaller well casing size than a compa- rable size of VTP. The real difference between the units is the potential prob- lems and solutions related to the electric motor. Because sub- mersibles use no other driver method than an electric motor, as well as the fact the motor operates in such a hostile electri- cal environment, problems associated with electrical issues will be much more relevant and common with a submersible than a comparable VTP. Most submersible pumps smaller than and equal to a 4- inch diameter pump are used primarily for domestic and indi- vidual residential water supply while the majority of larger submersible turbine pumps are designed for irrigation, com- mercial, municipal, and industrial water systems. Submersible pumps are currently the most popular type of deep well pump in use. Granted, when you're alluding to actual "well pumps," there are not currently too many choices. The shallow or deep well jet pumps are still relatively inex- pensive and easy to install, but they include priming require- ments. Therefore, they are still widely used on many shallow or deep wells under 100 feet, but are typically limited to cabins, vacation homes, or small residences. VTPs, on the other hand, are usually applied to medium to large capacity or moderate to high head applications due to their cost and complexity. Submersible pumps fit the bill for almost all applications. This class of pump can be used on well depths as shallow as Figure 2. Submersible motor types (4-inch diameter shown). Figure 1. Typical submersible pump motor construction and terminology. WATER WORKS from page 58 60 October 2015 WWJ waterwelljournal.com