“A positive displacement flowmeter is the only flow measurement technology that provides a true mechanical interface between the buyer and the seller;
the rotating element itself serves as the point of physical transaction.”

Positive Displacement flowmeters have been the original workhorses for accurate custody transfer measurement since the late 1930s. Among the many technologies available, PD flowmeters continue to offer unmatched repeatability, accuracy, and rugged design attributes that are critical when ownership of a valuable fluid changes hands.

Fluidyne’s oscillating piston flowmeters are available upto 1500 litres per minute and are the preferred choice for applications such as barge unloading systems, bunkering flowmeters and road tanker decanting unit.

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futuristic-technology-concept (1)

The Configuration of
Custody Transfer Measurement

Flowmeter – The Measurement Core

At the heart of custody transfer measurement is the flowmeter. Positive Displacement (PD), Coriolis, Ultrasonic, or Turbine flowmeters are commonly used. Fluidyne’s oscillating piston PD flowmeters offer unmatched accuracy of better than ±0.1% and are ideal for tanker decanting units, barge unloading systems, and bunkering operations.

These components remove entrained air and solid particles respectively before the fluid reaches the flowmeter. This ensures the custody transfer measurement is accurate and unaffected by non-liquid elements.

Flow control valves maintain a stable flow rate, avoiding pressure surges that could affect measurement precision during critical custody transfer operations. Fluidyne oscillating piston flowmeters are immune to variations in flow velocity or pipe-born vibration.

These devices convert mechanical movement into electronic signals, enabling integration with batch controllers and SCADA systems for automated custody transfer measurement.

The flow computer calculates totalized flow, applies temperature and pressure compensation, and logs transaction data. It’s essential for generating accurate, legal records.

Custody transfer measurement often requires compensation for temperature and pressure variations. Sensors provide real-time data to ensure accurate, corrected volume readings.

A printer provides a hard copy receipt of the transaction, including flow data, date/time, and buyer/seller info—essential for audit trails and legal compliance.

To maintain accuracy, custody transfer systems are regularly validated using master meters or provers, ensuring ongoing reliability and compliance.

Protocols like Modbus, Profibus, or SCADA allow remote monitoring, integration with ERP systems, and real-time data sharing between stakeholders.

Benefits

  • High Accuracy: Better than ±0.1% of reading with linearization techniques, making them ideal for legal metrology applications

  • Wide Viscosity Range: Performs well with low and high-viscosity fluids, including white oil, black oil, chemicals and blended products

  • Mechanical or Electronic Outputs: Pulse, HART, Foundation Fieldbus output options

  • Compact and Rugged: Designed for easy installation in tight or mobile setups such as skid systems or truck-mounted platforms.

  • Low Maintenance: Single rotor or connected rotor design, no metal-to-metal contact and robust construction ensure years of trouble-free service.

  • Calibration: Easy field calibration with master meter or volumetric prover

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futuristic-technology-concept (1)

Applications

Tanker Decanting Units

When fuels or chemicals are offloaded from road tankers to storage tanks, accuracy and speed are both critical. Fluidyne PD meters enable fast decanting while ensuring the exact volume delivered is recorded. With minimal installation requirements, these meters are well-suited for mobile and skid-mounted decanting units.

Marine terminals and barge operators rely on dependable flow measurement systems to monitor fuel and chemical transfer during unloading. Fluidyne’s PD flowmeters are robust enough to handle the challenging marine environment while offering the high accuracy necessary for invoicing and regulatory compliance.

Bunkering—the process of transferring fuel to ships—demands a high level of precision, especially with the increasing scrutiny of marine fuel transactions. Fluidyne’s flowmeters are a preferred choice for ship owners, terminal operators, and port authorities, as they deliver repeatable measurements and are compatible with automation systems for real-time monitoring and control.

In pipeline operations, custody transfer of liquids over long distances involves significant volumes and, by extension, significant financial value. PD flowmeters, with their high turndown ratio and proven accuracy, help eliminate disputes and support transparent accounting in downstream pipeline networks.

Features

  • Accuracy and repeatability of better than ±0.1%
  • Custody transfer measurement mode with sealing provision
  • Flowmeter with single rotor oscillating piston design
  • High capacity float-operated strainer cum air eliminators
  • Fluidyne-make Batch controller
  • Standard outputs like Pulse, Modbus, HART
  • Legal Metrology and PESO certified
  • OIML and IECEx certification in progress
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Related Product

Series 7100

Series 7100 – Tanker Decanting Systems

Series 6730

Series 6730 – Preset Batching Systems

FAQs

What is custody transfer measurement?

Custody transfer measurement is measurement of commercial fluid handover from one party to another involving financial transactions. The process is used where large volumes of hydrocarbons, chemicals or gases are exchanged in industries such as oil and gas, petrochemicals, marine and pipeline transportation.

Custody transfer demands high accuracy, repeatability and reliable measurement and in compliance with legal and metrological standards. Since large volume of fluids are transferred, every litre of fluid has to be measured with precision as it has a direct impact on price of ownership.

Fluidyne offers high precision oscillating piston flowmeters which are the main elements of custody transfer measurement. With accuracies of better than ±0.1% of reading,they are the industry standard of measurement in challenging applications.
Fluidyne also offers strainers, air eliminator, batch controllers and on-off valves to provide a complete custody transfer solution.

Custody transfer is a process used in the oil and gas, petrochemicals and fluid transportation industries. Examples of custody transfer are 

  • Bunkering – Fuel deliveries from barges to ships
  • Tanker decanting into storage tanks
  • Pipeline delivery
  • LPG or LNG terminal unloading
  • Chemical plant receiving raw material

Yes Fluidyne’s equipment are certified by Legal Metrology and also has the custody transfer mode in which calibration factors are protected against tampering.

Certifications for custody transfer ensure that measurement equipment and processes are legally compliant, traceable, and accurate enough for commercial transactions. These certifications are typically governed by international metrology standards and regional legal-for-trade regulations.

  • Use of high repeatability (better than ±0.1%)  oscillating piston type positive displacement flowmeter
  • Linearization techniques within the flowmeter calibration
  • Use of Fluidyne-manufactured air eliminators to prevent two-phase flow
  • Precision pulse generation mechanism
  • Accurate flow computer – Fluidyne batch controller