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Cranston, RI, USA, March 4, 2015 – Editor’s note: This is Part two of Water Technology’s February feature titled, “The factors that impact Venturi meter accuracy.” In Part one, the author discussed how the materials used and the time in service can impact a meter’s accuracy. If you missed Part one, please visit to read the entire article. For Part two of this article, factors such as minimum to maximum flow rate effects on discharge coefficient usage, secondary instrumentation limitations, undocumented flow pattern effects and more will be discussed.

Depending on manufacturer’s claims, the classical design of a Venturi meter maintained a constant discharge coefficient down to a pipe Reynolds number (Rd) of approximately 200,000. This simply means that as long as the minimum flow rate Rd is maintained above this value, the discharge coefficient of the classical design (which is 0.984, in most cases) remains constant. If, however, the flow rate drops below a pipe Rd level of 200,000, there is a bias error that must be applied to the discharge coefficient, which will progressively lower its value.



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144.0 Inch HVT Installation