Question

What is the role of a flow computer in LNG metering systems?

Accepted Answer

The role of a flow computer in LNG metering systems is to accurately calculate the mass, volume, and energy content of the LNG flowing through the metering system, correcting for the effects of temperature, pressure, and composition. Flow meters measure the volumetric flow rate of the LNG. However, the volume of LNG changes with temperature and pressure. A flow computer receives inputs from flow meters, temperature sensors, pressure sensors, and sometimes gas chromatographs (which measure composition). It uses these inputs to calculate the corrected volume, mass flow rate, and energy flow rate of the LNG. The flow computer applies standardized equations of state, such as the AGA NX-19 or GERG-2008, to correct for the effects of temperature and pressure on the LNG density. The gas chromatograph data is used to determine the composition of the LNG, which is necessary to calculate its heating value. The flow computer integrates the flow rate over time to determine the total amount of LNG that has passed through the metering system. Flow computers used for custody transfer applications must meet stringent accuracy requirements and be certified by regulatory agencies. They also typically have features such as audit trails, security measures, and communication interfaces to ensure data integrity and traceability. The accurate measurement of LNG flow is critical for commercial transactions and inventory management, and the flow computer is an essential component of any LNG metering system.

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What is the role of a flow computer in LNG metering systems?