Liquid Flow Calibrations
NIST provides calibration services for liquid flow meters. There are three primary calibration standards for liquid flow: two are volume based and one is gravimetric. The volumetric primary standards use a 5% propylene glycol and water mixture as the working fluid to match the properties of jet fuel, and are referred to as the 0.1 L/s Liquid Flow Standard and the 2.5 L/s Liquid Flow Standard. The gravimetric primary standard uses water as its working fluid and is called the 65 L/s Liquid Flow Standard.
The 0.1 L/s and the 2.5 L/s Liquid Flow Standards are piston provers. Flow determination is based on the piston displacing a known volume of liquid in a measured amount of time. The expanded uncertainty for the 0.1 L/s standard is 0.04% for flows from 0.003 L/s to 0.1 L/s and 0.07% for the 2.5 L/s standard for flows from 0.02 L/s to 2.5 L/s (k = 2). Pipe connections for calibrations using these standards should be A/N fittings and National Pipe Threads up to 2.54 cm (1 in) in diameter.
Because meters calibrated on the 0.1 L/s and the 2.5 L/s Liquid Flow Standards are typically used to meter hydrocarbon liquids and may contain parts that are not compatible with water, meters are cleaned and dried following calibration on these provers. Meters are rinsed with ethanol and then dried by capping off one end of the meter and applying vacuum to the other for approximately one hour. Meters may be treated with a lubricant following drying at the customer’s request.
The 65 L/s Liquid Flow Standard consists of a reservoir, pumps, meter runs, and a 3700 L weigh tank. The system operates as a constant flow facility, and uses timed collections of water to compute the average flow through the meter being calibrated. The expanded uncertainty for this facility is 0.05%, or less (k = 2) for flows from 0.67 L/s to 65 L/s. Pipe connections for calibrations using this standard should be ASA 150 lb steel flanges, VictaulicTM couplings, or adapters thereto.
Meters are accepted for calibration if the flow range and piping connections are suitable, and if the system to be tested has precision appropriate for calibration with the NIST flow measurement uncertainty.
A normal flow calibration includes five different flows, with five averages of the meter readings and the standard flow made at each set point. This entire test sequence is repeated on a second occasion to assess reproducibility. It is helpful if the customer specifies the flow set points and the instrumentation requirements of the meter (pressure, temperature, full scales required, etc.). The resulting calibration report includes an uncertainty analysis for the flow meter calibration factor, which includes the uncertainty of the primary flow standard, the uncertainty attributed to reproducibility of the meter under test, and the uncertainty of any customer provided instrumentation associated with measuring the flow meter output. (Note that the uncertainties in meter factor may be larger than the uncertainties of the primary standard due to extra reproducibility of the meter under test and the uncertainty of instrumentation associated with the meter under test).
Calibration fees for this and other services can be found in the Fee Schedule available online from the NIST Calibrations Website. To read more about our facilities, see the NIST Special Publication 250-1039r1 and NIST Special Publication 250-73.
To have your flow meter calibrated on one of the 0.1 L/s standard or the 2.5 L/s standard, contact Sherry Sheckels to schedule your calibration dates and to obtain estimated turn-around times.
To have your flow meter calibrated on the 65 L/s primary standard, contact Joey Boyd to schedule your calibration dates and to obtain estimated turn-around times.Details on ordering instructions, purchase orders, shipping, and Service ID Numbers, are available through NIST's Calibrations Website under policies for domestic customers and foreign customers.
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