Flow meters measure the volumetric or mass flow rate of liquids and gases in process, utility, and custody transfer applications. Calibration verifies flow measurement accuracy across the operating range using a reference flow standard such as a gravimetric prover or master meter. Flow measurement accuracy directly impacts process control, billing, and regulatory compliance.
Verify the flow meter is installed with proper upstream and downstream straight-run requirements. Confirm the configured pipe diameter, fluid type, and engineering units match the application. Record the meter serial number and firmware version.
With flow stopped and the meter filled with process fluid, verify the zero reading. Record the zero offset. For Coriolis meters, perform a zero calibration per manufacturer procedure if the offset exceeds specification.
Test at a minimum of five flow rates spanning the meter's turndown range (e.g., 10%, 25%, 50%, 75%, and 100% of maximum flow). At each point, collect the meter totalized reading and the reference standard accumulated value over the same time period.
Calculate the meter factor (K-factor) at each test point as the ratio of reference volume to indicated volume. Determine the linearity (spread of K-factors across the range) and the weighted mean meter factor.
At one flow rate (typically midrange), perform three consecutive runs and calculate the repeatability as the spread of meter factors. Repeatability must meet the meter's published specification.
Record all test data, environmental conditions, fluid properties, and reference standard information. Issue the calibration certificate with meter factors, linearity, and measurement uncertainty. Apply the calibration label.
Meter factor error at each test point must not exceed ±0.5% for custody transfer applications or ±1.0% for general process measurement. Repeatability must be within ±0.1% for custody transfer or ±0.25% for process applications. Linearity (spread of K-factors) must meet the manufacturer's specification.
12 months for process; 6 months for custody transfer
All flow meter technologies require calibration, including electromagnetic, Coriolis, ultrasonic, vortex, turbine, positive displacement, and differential pressure flow meters. Each technology has specific calibration requirements and sensitivities to installation conditions.
The meter factor is the ratio of the true flow (from the reference standard) to the indicated flow from the meter under test. A meter factor of 1.000 indicates perfect agreement. The meter factor is used to correct the meter's output for accurate flow measurement.
Yes, using portable master meters or clamp-on reference flow meters. However, field calibration typically has higher uncertainty than laboratory calibration with gravimetric or volumetric provers. Custody transfer meters usually require laboratory calibration or in-situ proving with a dedicated prover.
CalibrationOS tracks due dates, stores certificates, and generates audit-ready reports.
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