Gas Flow Calibrations
NIST Provides calibration services for gas flow meters using three pressure, volume, temperature, and time (PVTt) systems with collection tanks of 34 L, 677 L, and 26 m3 and a Working Gas Flow Standard (WGFS). The three PVTt standards cover flow ranges of (1) 0.001 L/min to 100 L/min, (2) 10 L/min to 2000 L/min, and (3) 900 L/min to 78,000 L/min, respectively. The 34 L PVTt can calibrate flow meters in any non-corrosive and non-hazardous gas that is available in pressurized cylinders, including nitrogen, argon, helium, etc. The uncertainty of the 34 L and 677 L PVTt standards is 0.025% (k = 2). The 26 m3 standard uses dry air and has a flow uncertainty of 0.09% (k = 2). To read more about our primary gas flow standards, see the following documents: 34 L and 677 L PVTt, NIST Special Publication 250-63; 26 m3 PVTt, NIST Special Publication 250-1046 .
The Working Gas Flow Standard (WGFS) uses critical flow venturis (CFV) and laminar flow meters that have been calibrated in the PVTt standards as working standards to calibrate customer flow meters. The uncertainty of the WGFS ranges from 0.15% to 0.07% (k = 2) depending on the combination of working standards used and the flow range. Pressure regulators provide CFV pressures up to 700 kPa. The gas source for the WGFS can be dried air from our compressor, nitrogen from a dewar (<150 L/min), or other gases from compressed gas cylinders (<100 L/min). To read more about the Working Gas Flow Standard, see NIST Special Publication 250-80.
The available fittings include national pipe thread (NPT), SwagelokTM, VCR, VCO, AN 37 degree flare, ASA 150 lb, ASA 300 lb, and ASA 600 lb. Pipe diameters range from 3 mm to 203 mm (1/8" to 8").
We deliver a calibration report that includes an uncertainty analysis for the flow meter calibration factor. This uncertainty includes the uncertainty of the flow standards given above as well as uncertainties related to instrumentation associated with the meter under test and its reproducibility. A normal flow calibration includes five flow set points (e.g., 200 kPa, 300 kPa, 400 kPa, 500 kPa, and 600 kPa for a CFV or at 10%, 25%, 50%, 75%, and 100% of the meter full scale for a laminar flow meter). At each of the five flows three (or more) measurements are gathered on two different occasions to assess the flow meter reproducibility. As a result, the tabulated data for the calibration are averages of six or more individual measurements. It is helpful if the customer specifies the flow set points and the instrumentation requirements of the meter (pressure, temperature, full scales required).
Calibration fees for this and other services can be found in the Fee Schedule available online from the NIST Calibrations Website.
To have your flow meters calibrated: