Water Well Journal
Issue link: http://read.dmtmag.com/i/655200
will work with the intended meter. And finally, verify the meter is rated for the system's working pressure range. Be sure the accuracy of the flowmeter is within pre- scribed limits for permit requirements. Most meters are de- signed for accurate operation within a range of ±1%-2% of the amount actually being pumped. Most, if not all, meters are calibrated at the factory and should operate well within ±5%. All flowmeters should be inspected periodically as part of a scheduled maintenance program, especially meters that have any moving parts. Meters generally are checked for two rea- sons: to confirm it is still operating or to assess its accuracy. Choosing the Right Flowmeter What type of flowmeter to install? It's just as important to know what a flowmeter cannot do as well as what it can do when selecting a meter. Each type and style has advantages and disadvantages—the degree of satis- factory performance is directly related to how well the capabilities and short- comings of a meter are matched to the requirements of the application. Users often expect performance from a meter that is not consistent with what the man- ufacturer has designed or what the sup- plier has provided. Most suppliers want to make sure the right flowmeter is installed and used for a particular system. Many provide ques- tionnaires, checklists, and specification sheets designed to obtain the critical in- formation necessary to match the correct flowmeter to the job. Technological improvements of flowmeters must also be considered. A common mistake is to select a technol- ogy that was popular for a given appli- cation some years ago and assume it is still the best instrument for the job. Chances are many changes and innovations have occurred in recent years in the development of flowmeters for that partic- ular application, making the choice much broader. One recent development is the availability of computer programs to perform the tedious calculations often necessary for selecting flowmeters. Calculations that used to take an hour can now be done in a matter of seconds. Refer to Table 1 for the advantages and disadvantages of currently available flowmeters for water and wastewater. Until next month, work safe and smart. WWJ Ed Butts, PE, CPI, is the chief engineer at 4B Engineering & Consulting, Salem, Oregon. He has more than 35 years experience in the water well business, specializing in engineering and business management. He can be reached at epbpe@juno.com. WWJ April 2016 41 Twitter @WaterWellJournl Type of flowmeter Conditions of water suited Pipe sizes Pressure loss Typical accuracy in percent Required length of straight pipe upstream of meter Required length of straight pipe downstream of pipe Cost Electromagnetic full pipe meter Few limitations 4, 6, 8 inch; larger sizes available by order None ±0.5% of rate 5 or less. Consult dealer and specification sheet 2 or less. Consult dealer and specification sheet Depends on brand and size of pipe (increases with pipe size) Electromagnetic insertion meter Few limitations 3 to 48 inches None ±1 of full scale 10 times the diameter of the pipe 5 times the diameter of the pipe Low to medium Ultrasonic (time-of-travel) Clean water with some particles of air bubbles 1 inch to 60 inches or more None ±2% of full scale 10 times the inside diameter of the pipe 5 times the inside diameter of the pipe Medium to high, depending on configuration needed and diameter of pipe Propeller Clean, relatively free of sediments preferred 2 to 96 inches Low ±2% of reading 5 to 10 diameters* 1 to 2 diameters* Low to high, depending on pipe size Differential pressure Clean to mildly dirty 5/8 inch to 72 inches Low ±0.1% to 2% 2-20 diameters* 0-10 diameters* Low Positive displacement Clean 5/8 inch to 4 inches Medium to high ±1.5% to 2% Minimal Minimal Low Vortex Clean to dirty 2 to 20 inches Low to medium ±1% of full scale 10 times the diameter of the pipe 5 times the diameter of the pipe Low to medium *Depends on system specifics T Table 1. Flowmeter selection chart R C N CTERIA! 096 2 . ORE, ALER! USH + WELL Jr. Blvd. • Lubbock, TX 79404 747.2096 • coteychemical.com N BA FOR CHOICE WEAPONS R W 806 7 U A M 7 4410 MLK 806.7