Water Well Journal
Issue link: https://read.dmtmag.com/i/655200
comprising 0's and 1's of varying periods in accordance with the flow being measured. The periods of 0 and 1 can then be measured to determine the speed and direction of rotation, and hence determine the rate of flow and amount of fluid over a period of time. Some flow measurement methods may generate analog signals that must be converted to digital signals before being used by a microprocessor. A fast flow generates a pulse/waveform of a higher frequency while a slow flow generates a lower frequency pulse/waveform. Methods of Flow Measurement The following represent a list of most, but not all, of the methods of flow measurement available for water and waste- water technologies. Differential pressure meters (Figure 1) for the inferred measurement of a liquid's rate of flow are well known and common. In fact, they are by far the most common in overall use today. It is estimated more than 50% of all liquid flow measurement applications use this type of meter. The basic operating principle of differential pressure flowmeters is based on the principle the pressure drop across the meter element is proportional to the square of the flow rate. The flow rate is obtained by measuring this pressure differential and extracting the square root. Differential pressure flowmeters, like most flowmeters, have a primary and secondary element. The primary element causes a change in kinetic energy in the fluid flow—often this is an inline orifice—which creates a differential pressure in the pipe on each side of the orifice. The unit must be properly matched to the pipe size, flow conditions, and the liquid's properties. In addition, the meas- urement accuracy of the element must be acceptable over a reasonable range. The secondary element measures the differential pressure across the primary element and provides the signal or readout that is converted to the actual flow value. Chief advantages to this technology include its simplicity, accuracy, and ability to be used with a wide range of differential pressure switches and sensors for control of pumps and other devices. Orifices are the most popular liquid flowmeters in use with differential pressure systems today. An orifice is simply a flat piece of metal with a specific-sized hole bored in it. Most ori- fices are of the concentric (round) type, but eccentric, conical (quadrant), and segmental designs are also available. In practice, the orifice plate is installed in the pipe under flow between two flanges. Acting as the primary device, the orifice constricts the flow of liquid to produce a differential pressure across the plate. Pressure taps on either side of the plate are used to detect the difference. Major advantages of orifices? They have no moving parts and their cost doesn't increase significantly with pipe size. Conical and quadrant orifices are relatively new. These ori- fices were developed primarily to measure liquids with low Reynolds numbers. Essentially constant flow coefficients can be maintained at Reynolds number values below 5000. Coni- cal orifice plates have an upstream bevel, the depth and angle ENGINEERING from page 37 waterwelljournal.com 38 April 2016 WWJ i Patent Submersible P alve V Pump Check V fi i alves ted VFD V alve V Pump Check V Valve VFD VFD VFD US M Made ith Stainless Ste With Stainless Steel Internals Strong Carbon St ell™ Mode Deep W Well™ Model 80DW VFD alve ell Check V Valve Well Check V a Flomatic Deep W Water Americ eel Internals teel Construction el 80DW VFD ater s first choice ca' alve V heck C emand D low F ariable V • Metal to M • Size range • Rated to 4 • Heavy Dut • Optional th • Low Frictio • Small OD Metal Seating ferent sizes from 2 e: 12 dif 4,400 PSI – Settings down ty Construction – supports , 8 Round Sho hreads NPT on Losses Body Dimension " thru 9 5/8" 3/4 2 n to 3,300 feet s heavy hanging load ort or Long Model 80 e n o h P s I s ʼ n y u r P 5 1 -VFD MDW • 7 9 7 9 - 1 6 7 ) 8 1 5 ( • 0 4 0 2 - 3 3 8 ) 0 0 8 ( : e 1 0 8 2 1 Y N , s l l a F s n e l G e v i r D d n a l ( : x a F m o c . c i t a m o l f @ c i t a m o l f : l i a m E m o c . c i t a m o l f . w w w • 8 9 7 9 - 1 6 7 ) 8 1 5 ( ) ( ) ( The Groundwater NGWA Association SM