The Ultimate Guide to Custody Metering Solution
Custody metering refers to the measurement of fluids that are bought, sold, or transported between different parties. Accuracy in custody metering is crucial as it directly impacts financial transactions and regulatory compliance.

Why Positive Displacement meter in Custody metering ?

PD meters are notable in custody metering for their ability to directly measure volume. In contrast to flow meters such as turbine meters or electromagnetic flow meters that depend on velocity readings (which may be influenced by variables like fluid density or turbulence), PD meters offer a precise tally of distinct volumes, guaranteeing accuracy and dependability in measurement.Positive displacement flow meters are favored in custody Transfer metering applications for several reasons:
  1. Accuracy: PD meters are known for their high accuracy, typically within ±0.1% of actual flow rate. This level of precision ensures that both buyers and sellers can trust the measurements for billing and auditing purposes.
  2. Viscosity Insensitivity: Unlike some other flow meter types, PD meters are relatively insensitive to changes in fluid viscosity. This makes them suitable for measuring a wide range of fluids, from light hydrocarbons to heavy crude oils.
  3. Low Flow Capability: PD meters excel at measuring low flow rates accurately, which is often a requirement in custody transfer scenarios where even small errors can lead to significant financial discrepancies.
  4. Long-Term Stability: With proper maintenance, PD meters can maintain their accuracy over extended periods, reducing the frequency of recalibrations and ensuring consistent performance over the meter’s lifespan.

Importance of W&M certifications:

W&M approvals for custody meters are crucial as they ensure legal compliance, accuracy in measurement, fairness in commercial transactions, stakeholder confidence, quality assurance, regulatory compliance, and global acceptance.
  1. Legal Compliance and Regulatory Standards: W&M approvals, guarantee custody meters meet accuracy, reliability, and performance criteria for commercial transactions. Compliance with these standards through rigorous testing and certification processes is crucial for accurate billing and financial transactions.
  2. Accuracy: Custody transfers involve exchanging valuable commodities like oil, gas, and chemicals. Metering system accuracy is crucial for fair financial transactions, preventing disputes, and ensuring trust in commercial dealings.
  3. Global Acceptance and Interoperability: W&M approvals align with international standards from organizations like OIML and NIST, ensuring custody meters are accepted globally. This alignment supports consistency in measurement standards, facilitates international trade, and reduces barriers to market entry for custody meter manufacturers and users.

Liquid Controls, IDEX Energy brand

Liquid Controls, under the IDEX Energy brand of Advanced Flow Solutions (AFS), is a leading global provider of precision measuring systems for transferring refined fuels and liquids since 1954.Liquid Controls offers a versatile range of Positive Displacement Metering solutions which combine world renowned Liquid Controls flow meters with Electronic register & industry proven Digital control valve for optimum performance.Metering Components:
  1. Liquid Controls PD meter with pulser
  2. Liquid Controls Strainer cum Air Eliminator
  3. Electronic Register / Batch controller
  4. Multistage Digital Control Valve / DSSV
Liquid control metering systems are majorly supplied in various downstream segments such as terminal automation systems, tank truck loading/unloading, and the aviation industry.

Key Benefits of Liquid Control Flow Meters:

  1. Accuracy and Precise measurement: Liquid Controls (LC) flow meters are known for their specialized Tri-Rotor design. There is no metal-to-metal contact within the metering element…and no contact means no wear…no wear means no increase in clearances…no increase in clearances means no increase in slippage…and no increase in slippage means no deterioration in accuracy. This helps in sustaining the accuracy over longest period of time. Metering system ensures sustained accuracy better than +/- 0.05% and 0.02% repeatability.
  2. Accurate Measurement at Low Flow Rates: In custody transfer applications, accurately measuring low flow rates is critical. Liquid Controls meters excel in measuring low flow rates with high precision, ensuring that all quantities transferred are accurately recorded, regardless of the flow rate.
  3. Safety & Security: Pulsers are with Dual quadrature channel pulse output to electronic flow controller (90 degrees apart) complying to Level A security as per API Chapter 5.5 Fidelity & Security of flow measurement. Multiple level authentication password, OTP features for calibration, E3+M3 Qualification, ISO 7637-2 compliance & W&M sealing ensures safety & security of the metering system.
  4. Digital and Electronic Integration: Liquid Controls meters are typically certified and compliant with industry standards and regulatory requirements, including OIML, W&M (Weights and Measures), CCOE & ATEX approvals.
  5. Single Source Solution: Liquid Controls presents an all-inclusive metering system comprising a PD Flow meter, strainer, Air Eliminator, Digital Flow controller, and Batch controller. This comprehensive package signifies their commitment to managing the entire metering system, guaranteeing accurate, reliable, and smooth operation.
  6. Low Maintenance Requirements: Due to their specialized design and quality materials, Liquid Controls flow meters have low maintenance requirements. They are designed to withstand wear and corrosion, reducing downtime and maintenance costs associated with recalibration and repairs.
  7. Compliance and Certification: Liquid Controls meters are typically certified and compliant with industry standards and regulatory requirements, including OIML, Nmi, W&M (Weights and Measures), ATEX & PESO approvals. This ensures that they meet legal metrology standards for accuracy, reliability, and traceability, making them suitable for custody transfer operations where compliance is paramount.
Key markets :Liquid Controls robust design, accuracy across varying conditions, and ability to handle different fluid viscosities makes a preferred choice for industries such as oil and gas, petrochemicals, and other industrial applications.

Below are the applications where LC PD flow meters are widely used in oil & gas segment :

  1. Refined Products Transfer : Positive displacement flow meters are used in custody transfer of refined products such as gasoline, diesel, jet fuel, and lubricants. They are used in Highly precise Custody Metering solutions in terminal Automation TAS –  Tank truck/Wagon loading & unloading applications, Fuel dispenser / Fuel Bowser of refined hydrocarbons.
  2. LPG Metering : PD flow meters are employed to measure LPG flows accurately during custody transfer, ensuring that the quantities sold or transferred are exact, which is crucial given the high value of LPG.
  3. Biofuels : With increasing focus on renewable energy sources, biofuels like ethanol and biodiesel are becoming more prevalent in the downstream oil & gas sector. PD flow meters are suitable for custody applications involving biofuels, providing accurate measurement despite their different properties compared to traditional fossil fuels.
  4. Aviation Fueling : LC PD meter in aircraft refueller operations, which ensure the correct amount of fuel is delivered to aircraft, meeting stringent quality and quantity standards.


When it comes to accuracy and dependability, it’s important to look at players in the industry like Liquid Controls. We at Liquid Controls support you right from the inception, design, Engineering, procurement, commissioning, training, after market service & take ownership of the entire metering system.