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Pressure Drop and Flow Capacity Testing
The efficiency of pipe fittings and components in conveying water is an important factor in designing plumbing systems. The Engineering Lab offers a wide range of pressure drop and flow capacity tests for evaluating valves, fittings, filters and other components. Manufacturers can rely on NSF to certify their fittings to ASME, ASSE, AWWA, CSA, NSF, and EPA WaterSense standards, as well as verify their marketing claims.
Engineering Principles - The pressure drop (dP) in a fitting is related to the square of the flow rate (Q). A common method for rating the efficiency of a fitting is by measuring the flow coefficient Cv. The Cv is the number of gallons per minute that will pass through a fitting with a pressure drop of 1 psi. For water, the formula is dP = (Q / Cv)^2. The flow coefficient Cv is a useful parameter used by engineers when designing piping systems. Based on these engineering principles, we can measure and calculate a wide range of other useful parameters (see applications below).
Capabilities (THINK BIG, MEASURE SMALL)
Think Big - The Engineering Lab can test flow rates up to 6000 gallons per minute. The lab is equipped with one 12000-gallon resevoir and two 4000-gallon reservoirs connected with 14 inch pipe to a 50 hp pump.
Measure Small - The Engineering Lab has a wide range of instrument capabilities for measuring pressure drop. The pressure drop in larger fittings is often below 1 psi at their intended flow rates. The lab is equipped with precision differential pressure gauges with resolutions of 0.001 psi and accuracies of 0.28% full scale. The data can be sampled every 0.0001 seconds and averaged with data acquisition to smooth out turbulence in the system.
Applications
EPA WaterSense Faucet Certification - The EPA has developed standards for maximum and minimum flow rates for water-efficient faucets over a range of inlet pressures. The Engineering Lab can certify your faucets and aerators to the EPA WaterSense Standard.
Equivalent Length Measurement (fittings) - A measure of the resistance to flow. It is defined as the length of pipe that would have the same pressure drop as the fitting being measured at a particular flow rate.
Pressure drop at rated flow (flexible connectors) - ASME A112.18.6 / CSA B125.6 specifies the maximum allowable pressure drop in flexible connectors at a defined flow rate.
Flow capacity at rated pressure (faucets) - ASME A112.18.1 / CSA B125.1 specifies the minimum and/or maximum flow rates allowed for fixture fittings at particular inlet pressures.
Cv and Kv Measurements (valves and fittings) - The ASME A112.4.14 ball valve standard requires a minimum Cv value for each valve size. In SI units, the flow factor is called Kv and is related to the Cv = Kv * 0.07.
For more information on the engineering laboratories, visit the engineering lab web page or email frayer@nsf.org.