ISO 7278-1:1987

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.