Flow Meter Calibration & Verification
Flow is the measurement most often used to bill, to balance and to control — and the one that drifts most quietly. A coated electrode, a worn bearing, a changed fluid or a disturbed flow profile shifts the reading long before anything alarms. SEMAC verifies flow meters where they are installed, comparing them against a calibrated master meter under real process conditions.
What we calibrate
Electromagnetic flow meters
Coating, electrode fouling and liner wear are the usual causes of drift; onboard diagnostics plus a reference comparison separate a real error from a signal problem.
Ultrasonic — clamp-on and inline
Transit-time meters are highly sensitive to installation and flow profile. Clamp-on units also let us add a temporary reference to a line with no spool piece.
Coriolis mass flow meters
Zero stability and tube condition dominate accuracy. We check zero under process conditions and verify mass and density readings.
Vortex and turbine meters
Mechanical wear and deposits change the K-factor. A comparison against a reference shows how far the factory factor has moved.
Thermal mass flow meters
Gas composition changes invalidate the original calibration. We verify against the actual gas and operating envelope.
Differential pressure / orifice systems
The plate, the taps and the transmitter each contribute error. We calibrate the DP loop and check the primary element condition.
Water meters and rotameters
Utility and sub-metering points that quietly decide cost allocation and mass balance.
How we do it
Master-meter comparison, in seriesA calibrated reference meter is installed in series with the meter under test and both are read simultaneously across the working range — three to five flow points, each repeated, at a minimum of 180 seconds per run. This is the core method, and the deliverable is the relative deviation at each point with its repeatability and uncertainty. See the full walkthrough on the process page. In-situ verification via onboard diagnosticsModern meters can self-check coil, electrode and tube integrity against factory fingerprints. Fast, non-invasive, and a good first filter before a full comparison. For KROHNE devices we run this with the manufacturer’s own OPTICHECK Master handheld — see below. Temporary clamp-on referenceWhere the line cannot be broken to fit a spool piece, a clamp-on ultrasonic reference gives an independent second opinion on the same flow. Volumetric / gravimetric comparisonWhere a vessel, weighbridge or calibrated tank is available, collected volume or mass provides the most direct reference of all. Loop and output calibrationThe sensor is only half the chain. We verify the 4–20 mA / pulse / HART output and what the control system actually records.
Isometric diagram of a calibration setup. Fluid flows from left to right through a pipe. It passes first through the master meter, the traceable reference instrument, then along a straight run of ten pipe diameters into the meter under test, and leaves through a further straight run of five pipe diameters. Both straight runs belong to the meter under test and are provided where its type requires them. A data acquisition unit below reads both meters at the same time and calculates the percentage deviation between them.
OPTICHECK Master
Handheld for in-depth verification, device commissioning and monitoring of KROHNE field devices
On-site performance check and verification (levels 0, 1 and 2)Runs without interrupting the process — the device stays in the line and in service while it is checked in progressively greater depth against its factory fingerprint. Convenient commissioning of field devicesSet-up in the field, including zero calibration, so a newly installed or replaced device starts from a known, documented state instead of an assumed one. Proof-test and quality-system documentationDetailed reports for proof test documentation of safety loops in line with IEC 61508 / IEC 61511, and for quality management systems under ISO 9001.
What you receive
Calibration report or certificate per measurement point As-found and as-left verification sheets, issued separately, so drift over time becomes visible Relative deviation at each tested flow rate, expressed as % of reading Repeatability across the repeat runs at each rate, with the number of runs recorded The reference instrument used and its traceability chain Expanded measurement uncertainty for the comparison, with its coverage factor and confidence level The temperature and pressure of the working fluid during the runs Findings on installation, straight runs and flow profile Recommended corrective actions and next calibration interval For supported KROHNE devices: proof-test documentation for safety loops, in line with IEC 61508 / IEC 61511
When you need it
A safety-loop proof test is due
Where a flow measurement forms part of a protective function, the safety case assumes it still reads correctly. A documented proof test is the evidence for that assumption.
Mass balance no longer closes
Inputs and outputs disagree by more than the accepted tolerance and nobody can say which meter is wrong.
Custody transfer or billing
The meter decides what is invoiced. A documented error percentage is the difference between a defensible invoice and a dispute.
An audit is coming
ISO 9001 / ISO 14001 and environmental permits expect evidence that critical measurements are controlled.
The process changed
A new fluid, a different temperature, a modified pipe run or a replaced pump can invalidate the original calibration.
Batch or product quality drifted
Recipe dosing errors trace back to flow measurement more often than to the recipe itself.
A sensible starting point for a critical flow point is annual verification, with custody-transfer and billing meters checked more often and stable utility points less often. The right interval is not a guess: once two or three as-found records exist, the observed drift tells you whether to stretch the interval or tighten it. We set an initial interval based on the duty and revise it from your own history.
Calibration procedures follow ISO/IEC 17025 methodology; ESYD accreditation is in progress.
Industries served
Common questions
Tell us about the measurement point you need checked
Describe the instrument and your plant, and we will tell you what can be verified in-situ, what needs a workshop calibration, and what it will take.
Keep your instrumentation performing at its best
Speak with SEMAC's service team to discuss your maintenance needs and plan your verification & calibration service.