--- title: "Meter Proving and Flow Computers Explained | Citia" description: "Meter proving tests a flowmeter against a known volume to find its meter factor; a flow computer applies it. Compare prover types and see when to prove." url: https://citia-engineering.com/en/knowledge/meter-proving-flow-computer language: en updated: 2026-11-13 type: article site: Citia Engineering Indonesia --- # Meter proving and flow computers: keeping fuel metering accurate Meter proving tests a flowmeter against a known volume to give a meter factor; a flow computer applies it. Prover types, calculation and proving intervals. | Field | Value | | --- | --- | | Topic | Metering | | Author | Tim Engineering Citia | | Updated | 2026-11-13 | Key takeaways Meter proving is the test of a flowmeter against a known reference volume to produce a meter factor, while a flow computer applies that meter factor, together with temperature and pressure corrections, to calculate the standard volume of fuel delivered. A meter that was accurate on the day of commissioning does not stay that way. Proving is how a terminal finds out how far it has moved, and the flow computer is where the answer is put to work. This guide is a technical follow-up to flowmeters for fuel . It covers the proving chain, how a meter factor is calculated, the types of prover, what a flow computer does and when to prove. - Meter proving tests a flowmeter against a known reference volume and produces a meter factor, the correction that makes the meter's reading match the reference. - A flow computer applies the meter factor together with temperature and pressure corrections to turn the meter's raw signal into volume at base conditions. - Provers differ in size and speed: a test measure is simple and slow, a pipe or small volume prover is continuous, and a master meter is a portable shortcut with its own uncertainty. - Proving has no single interval; operators prove after repairs and product changes, then watch the meter factor trend for drift. ## The proving chain, from prover to report Proving is a comparison, repeated until the runs agree. The meter and the prover see the same flow of fuel. Several consecutive runs are taken at a steady flow rate, and the result is accepted only when the runs repeat within the limit set by the applicable procedure, such as API MPMS Chapter 4.8 on the operation of proving systems. Temperature and pressure at the prover and at the meter are recorded, because both volumes must be brought to the same conditions before they are compared. - Prover: Passes a known, calibrated volume past the meter. - Meter under test: Registers its pulses for the same volume. - Proving calculation: Compares the two volumes and checks the runs agree. - Flow computer: Stores the meter factor and applies it to every batch. - Report: Proving report and batch tickets with corrected volume. ## How a meter factor is calculated A meter factor is the reference volume divided by the volume the meter indicated, both corrected to the same conditions. A factor of exactly one means the meter agrees with the reference. A factor above one means the meter reads low, so its readings are multiplied up; below one means it reads high. The example on the right uses round, made-up numbers to show the arithmetic. Do not confuse the meter factor with the K-factor. The K-factor is the number of pulses the meter emits per unit of volume, set by the meter's design. The meter factor is the small correction found by proving, applied on top of it. ``` Prover volume at base conditions : 1 000.00 L Meter volume at the same conditions : 998.00 L Meter factor = 1 000.00 / 998.00 = 1.0020 Later batch, meter indicates 5 000.0 L Corrected volume = 5 000.0 x 1.0020 = 5 010.0 L ``` Illustrative values only, not from a Citia project. ## Prover types compared - How it works: Fuel fills a calibrated vessel; the level is read at the neck | A sphere or piston travels between detectors over a calibrated length | A piston in a short calibrated volume; pulse interpolation adds resolution | A reference meter, itself proved, runs in series with the meter under test - Good for: Small meters, loading bays, aviation fuel | High flows, pipelines, marine transfer | Sites that want a compact fixed unit | Many meters, no room for a fixed prover - Limits: Manual, slower, volume per run is small | Large footprint and cost | Needs good detector and electronics care | Adds its own uncertainty to the chain ## What a flow computer calculates A flow computer turns the meter's signal into a quantity that both parties can sign. It is a dedicated device, not a general PLC, so its calculations are fixed, auditable and sealed. The calculation method follows API MPMS Chapter 12.2 on petroleum quantities from dynamic measurement, with temperature and pressure factors from the API tables. OIML R 117-1 adds that a correction device is an integral part of the meter, and that the uncorrected quantity shall not be shown in normal operation. It also forbids adjusting a meter by means of a bypass. - Count the pulses: Convert pulses to indicated volume with the K-factor. - Apply the meter factor: Multiply by the factor found at the last proving, for that product and flow rate. - Correct for temperature: Apply the temperature correction to bring volume to base conditions. - Correct for pressure: Apply the pressure correction where the product and pressure make it matter. - Report the quantity: Send gross and standard volume to the batch record, ticket and terminal system. ## When to prove a meter There is no single proving interval; the contract, the regulator and the meter's history set it. Operators usually prove after a meter is installed, repaired or opened, after a change of product, when the flow range changes, and on a routine schedule. They then plot the meter factor over time. A slow trend suggests wear or fouling. A step change points to a mechanical event, a different product or a set-up error. A factor that jumps between provings deserves a look at the prover and the temperature probes before the meter is blamed. Proving is the technical routine; tera ulang is the legal one, and both belong in the maintenance plan. ## Field notes: a flow computer in aviation fuel metering At Pertamina Pulau Layang, the Citia aviation fuel metering integration uses an ISOIL VEGA II as the flow computer. It acquires and processes metering data from the field instruments. CS-Flow runs the dispatch logic, and the Machine User Interface identifies the user, takes the transaction by barcode and shows the filling in real time. The page lists flow rate, gross volume, net volume, preset, loaded volume, temperature and status among the values operators monitor, and says the integration improves traceability and reduces manual recording errors. Details are in the Pulau Layang project . For how the batch controller relates, see what a batch controller does . ## Glossary Field tip: prove the way you run: Prove at the flow rate and with the product the meter actually sees in service, and record the product, temperature and flow rate with every proving. A factor found at a gentle test rate can differ from the one that applies during a fast fill. - Meter factor: Reference volume divided by the meter's indicated volume at the same conditions. - K-factor: Pulses emitted per unit of volume, set by the meter design. - Prover: Equipment that supplies a known volume to test a meter. - Master meter: A reference meter, itself proved, used to prove other meters. - Pulse interpolation: A technique that resolves fractions of a pulse so a short prover volume can give a precise result. - Base conditions: The reference temperature and pressure to which volumes are converted. - Flow computer: A dedicated device that calculates delivered quantity from the meter signal. ## Frequently asked questions Q: What is a meter prover? A: A meter prover is equipment that passes a known, calibrated volume through or past a flowmeter so the meter can be tested. Common types are the test measure, the pipe prover, the small volume prover and the master meter, which differ in size, speed and cost. Q: What is a meter factor? A: A meter factor is the reference volume divided by the volume the meter indicated, both at the same conditions. A factor of one means the meter agrees with the reference, and the flow computer multiplies later readings by the factor to correct them. Q: How often should a flowmeter be proved? A: There is no single interval; it is set by the contract, the regulator and the meter's history. Operators usually prove after repairs, product changes and flow range changes, plus on a routine schedule, then trend the meter factor to see drift. Q: What is the difference between a flow computer and a batch controller? A: A flow computer calculates the delivered quantity, while a batch controller runs the loading: it opens and closes the valve and stops at the preset. At some bays one device does both, and at others they are separate and exchange data. Q: Does a flow computer replace proving? A: No, a flow computer only applies the meter factor that proving produces. Without proving, the factor goes stale and the computer keeps calculating from an old number, so both are needed. ## Sources and further reading 1. API MPMS Chapter 4.8: Operation of Proving Systems, American Petroleum Institute (listing by NSAI), 2021 (https://shop.standards.ie/en-ie/standards/api-mpms-chapter-4-8-2021-97736_saig_api_api_3006221) 2. API MPMS Chapter 12.2: Calculation of Petroleum Quantities Using Dynamic Measurement Methods, American Petroleum Institute (listing by BSI) (https://knowledge.bsigroup.com/products/calculation-of-petroleum-quantities-using-dynamic-measurement-methods-and-volumetric-correction-factors-part-1-introduction) 3. OIML R 117-1 (2019): Dynamic measuring systems for liquids other than water, Part 1, International Organization of Legal Metrology (OIML), 2019 (https://www.oiml.org/en/files/pdf_r/r117-1-e19.pdf) 4. OIML R 117-2 (2019): Metrological controls and performance tests, International Organization of Legal Metrology (OIML), 2019 (https://www.oiml.org/en/files/pdf_r/r117-2-e19.pdf) 5. Pertamina Pulau Layang: aviation fuel metering integration, PT Citia Engineering Indonesia, 2025 (https://citia-engineering.com/en/projects/pertamina-pulau-layang-aviation-fuel-metering-integration) 6. Cover photo by HomeSpot HQ, CC BY 2.0 (cropped and colour graded), Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Gas_Meter_(8845661187).jpg) Questions about metering at your terminal?: Describe the meters, the bay and the control system to siTia, and the engineering team will follow up. ## Contact - Company: PT Citia Engineering Indonesia - siTia - Virtual Assistance: [WhatsApp +62 813-2206-507](https://wa.me/628132206507). siTia answers questions about our products, projects and enquiries on WhatsApp. Replies are automated, and a person from the Citia team follows up. - Email: services@citiaengineering.com - Phone / WhatsApp (siTia): +62 813-2206-507 - Location: Bandung, Indonesia [Contact Citia](https://citia-engineering.com/en/contact.md) ## Structured data (JSON-LD) ```json { "@context": "https://schema.org", "@graph": [ { "@type": "Organization", "@id": "https://citia-engineering.com/#organization", "name": "Citia Engineering Indonesia", "legalName": "PT Citia Engineering Indonesia", "alternateName": "Citia", "url": "https://citia-engineering.com", "logo": { "@type": "ImageObject", "url": "https://citia-engineering.com/media/citia-logo.png", "width": 950, "height": 328 }, "description": "Citia is an engineering and system integration company in Bandung, Indonesia. 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