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Non-invasive, multi-channel ultrasonic gas flow measurement technology is offering a range of benefits within the often challenging petrochemical industrial environment, with no opening of the pipeline necessary for installation or maintenance. The ultrasonic flowmeters are simply attached to the outside of the pipe, and a particularly high measuring accuracy is achieved through 4 ultrasonic beams installed in reflect mode, and 8 independent ultrasonic paths travelling through the gas to improve flow averaging of up to 4 planes of the pipe section.

FLEXIM assisted a major French chemical manufacturer looking for an alternative technical approach to the internal fiscal metering of ethylene gas. Measuring the mass flow of ethylene gas for internal accounting was the task at the manufacturer’s petrochemical cluster, where a steam cracker produces raw materials including ethylene and propylene, which are of great importance to the plastics industry.

At the manufacturer’s site, the ethylene gas flow had historically been measured using an MID approved gas measuring station, consisting of a vortex flowmeter and a density measurement, but this was vulnerable to deposits of paraffin carried by the ethylene flow. These deposits can form on the bluff body in the meter, which over time change the vortex formation leading to drifting measuring values.

A fresh approach was needed, to resolve the problem faced by the inline ethylene gas fiscal metering and deliver a more accurate alternative.

The deviations were clear to see from the balance of the incoming and outgoing quantities at the polyethylene production facilities, so FLEXIM used a four channel ultrasonic flowmeter to count the quantity of the ethylene gas mass flow, which proved to be highly accurate and offered ease of maintenance, as unlike the wetted measuring system it doesn’t need to be shut-off for servicing.

Reliable and accurate flow measurement is achieved, with excellent 0.15% reproducibility of the measured value ±0.005 m/s.

Measuring the amount of ethylene gas in polyethylene production is essential, so a second dual channel device was also installed, which was calibrated against the reference measurement of the highly precise four channel ultrasonic flowmeter. Internal billing of liquid and gas flows between different production units at the manufacturer’s site is subject to stringent metrological controls, so for that reason the measuring accuracy of the ultrasonic flowmeter was tested in a calibration laboratory in accordance with ISO 17025.

Before the final decision was made to permanently implement non-invasive measuring technology, strict monitoring against the existing fiscal gas station was carried out for a year, with performance proven to be fully adequate.

Under FLEXIM’s guidance, ultrasonic flowmeters have successfully replaced a recognised fiscal metering procedure, providing superior measurement accuracy for internal company to company billing.

For more information on the benefits of non-invasive multi-channel gas flow measurement technology in the petrochemical industrial setting, contact Simon Millington -www.flexim.co.uk | sales@flexim.co.uk | +44 (0)1606 781 420

External URL: https://www.flexim.co.uk