Company Profile

Flow Meter for Hydro Carbon Industry Standards: API-Compliant Custody Transfer Sizing

Quick Answer: For hydrocarbon custody transfer, start with the API MPMS Chapter 5 series and the contract accuracy limit instead of only matching the pipe size. A Coriolis mass flow meter from Silver Automation Instruments fits most liquid hydrocarbon lines from DN15 to DN300 with repeatability of 0.1 percent to 0.2 percent. Send us your pressure (bar), temperature (°C), pipe size (DN), and flow range for a sized quotation.

Why API compliance changes meter sizing

Many engineers size a hydrocarbon meter by pipe diameter. That is the first error. API custody transfer is a legal and commercial measurement, not a process indicator. But the meter has to prove repeatable under changing pressure, temperature, and density. API MPMS Chapter 5.6 for Coriolis meters and Chapter 5.8 for inline ultrasonic meters set the performance requirements for liquid hydrocarbons.

Here is the thing. A DN100 pipe does not always need a DN100 meter. A DN80 Coriolis meter may perform better on a diesel line flowing 10 to 30 m3/h. The DN80 meter stays in its calibrated sweet spot. Oversizing creates low-velocity errors and proving failures.

In practice, we start sizing at 70 percent of the maximum contract flow instead of matching the pipe diameter. So the meter remains inside the calibrated range during normal operation and during proving runs.

Sizing inputs for API-compliant custody transfer

Send us these values first:

Fluid name or product group

Operating pressure in bara

Temperature in °C

Flow range in kg/h or m3/h

Viscosity in cP

Density in kg/m3

Pipe size in DN

Most engineers skip the viscosity data. For heavy hydrocarbons like fuel oil or crude above 50 cP, viscosity correction changes the pressure drop and may move the meter from DN50 to DN80. We have seen this on customer sites many times.

Meter types for hydrocarbon custody transfer

Silver Automation Instruments is a flow meter manufacturer and supplier for hydrocarbon custody transfer projects in Southeast Asia, Oceania, Latin America, Africa, and the Middle East. We supply and calibrate flow meters for oil and gas terminals, refineries, and chemical plants.

Coriolis mass flow meters. Coriolis meters measure mass directly. Coriolis meters do not need density compensation for mass output. Use them for crude oil, refined fuels, LPG, solvents, and chemicals. Accuracy is typically 0.1 percent to 0.2 percent for liquids. API MPMS Chapter 5.6 applies.

Inline ultrasonic flow meters. Inline ultrasonic meters suit large refined product pipelines and terminal loading systems from DN100 to DN600. Use them where pressure drop is limited and a proving skid is installed. API MPMS Chapter 5.8 applies.

Oval gear positive displacement meters. Oval gear meters suit diesel, fuel oil, and high-viscosity hydrocarbon where exact batch volume matters. Use them for lower flow ranges and fiscal batching on road tanker loading.

For most custody transfer projects, Silver Instruments specifies a Coriolis mass flow meter in DN25 to DN150 with 4-20 mA HART, Modbus RTU, and ATEX Zone 1 approval. For terminal pipelines above DN200, we specify an inline ultrasonic flow meter with dual-path or four-path transducers and a flow computer input.

Example pairing for a diesel terminal line

Example pair: a diesel terminal line at 15 to 25 m3/h, 820 kg/m3, 3.5 cP, DN80 pipe, 35 °C, and 6 bara. Silver Instruments would specify a DN50 Coriolis mass flow meter with 0.15 percent accuracy and HART output. The upper range is 30 m3/h. The meter stays between 50 percent and 85 percent of calibrated range during normal loading.

Why proving and pressure drop change sizing

API custody transfer requires proving. A mete