Overview
ISO 7278-1:1987 - "Liquid hydrocarbons - Dynamic measurement - Proving systems for volumetric meters - Part 1: General principles" sets out the fundamental principles for proving volumetric meters used in dynamic measurement of liquid hydrocarbons. It defines objectives, prover types, basic procedures and general requirements to determine a meter’s relative error or meter factor as a function of flow rate and influencing parameters (temperature, pressure, viscosity).
Key topics and requirements
- Proving objectives
- Determine relative error or meter factor for corrections or adjustment.
- Two common goals: adjust registration for intermittent deliveries, or determine meter factor/relationship for continuous measurement.
- Types of provers covered
- Tank provers, pipe provers (unidirectional and bidirectional), and master meters.
- Precision bore (tube) provers are described as a special pipe prover variant.
- Test conditions and fluid properties
- Meters should be proved at expected operating flow, pressure and temperature, and on the same liquid where feasible.
- If proving on a different liquid, density and viscosity must be close or a known relationship used.
- Procedures and repeatability
- Standing start-and-stop and running start-and-stop procedures are defined.
- Each calibration point should be repeated at least twice, preferably three times, to ensure repeatability.
- Results and calculations must be recorded on an appropriate proving report.
- Measurement quality and uncertainty
- Guidance to limit uncertainties (e.g., pulse-generator proving should obtain at least 10 000 pulses per proving run unless pulse-interpolation is used).
- Meter factors are to be rounded to four decimal places for reporting.
- Practical considerations
- Avoid evaporation of high-vapour-pressure liquids; use mitigation (e.g., top spray in open tank provers) where necessary.
- Inspection, maintenance and pre-run trial checks are recommended to ensure prover integrity and stable conditions.
Applications and users
- Petroleum terminals, bulk plants and loading racks performing custody transfer and inventory control.
- Meter manufacturers, calibration laboratories and operators of pipeline and truck-loading systems.
- Regulatory and inspection bodies involved in metrological verification of volumetric meters for liquid hydrocarbons.
- Useful wherever accurate dynamic volumetric measurement or transfer of liquid hydrocarbons is required.
Related standards
- ISO 4124 (referenced in the document) - statistical control of volumetric metering systems.
- Subsequent parts of ISO 7278 (in preparation) cover detailed descriptions of pipe provers, tank provers and pulse-interpolation techniques.
Keywords: ISO 7278-1, liquid hydrocarbons, proving systems, volumetric meters, dynamic measurement, tank prover, pipe prover, master meter, meter factor, meter proving, meter calibration, pulse interpolation.
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