Independent tests carried out in the Middle East have demonstrated that Rheonik Coriolis large size flowmeters from GE’s Measurement & Control, can now be calibrated on compact provers without the need for intermediate turbine meters to validate use for custody transfer.
Pipe provers have been used in the oil and gas industry for many years to prove meters to custody transfer and fiscal standards. Over the past 20 years, small volume or compact provers have proved a viable alternative but experience has shown that certain types of meter do not calibrate well because of the small volumes used in compact provers. Coriolis meters have been particularly difficult to prove using this equipment because these meters, which measure mass flow, use a sampling and calculation system that integrates data over a short period and produces an output which lags behind the actual flow at any point in time. If this integration period is not compatible with the time taken for the piston of a small volume prover to complete its pass between detectors, then errors will occur. Historically, one way around this problem has been first to prove a turbine meter over the required flow range, and then use this proven meter as the transfer standard for the Coriolis meter.
The latest tests have been carried out using only a compact prover, an Omni flow computer and a density meter. The configuration involved setting up the flow computer to accept the density measurement at the flowmeter outlet connection. The verified results show an average stable meter factor and a repeatability of less than 0,1% and the flowmeter’s proven ranged go up to 12”.
As Uwe Hettrich, product manager for GE’s Rheonik product line, explains, “The Rheonik Omega tube Coriolis meter is one of the most versatile meters on the market. It offers high accuracy and fast response and is unaffected by viscosity, density or pressure changes. It can be used in an extremely wide range of line sizes, pressures and temperatures and has hazardous area approvals covering most of the world. Its ability to be calibrated by a compact prover, without the need for an intermediate turbine meter, further extends its versatility.”
The performance capabilities of the Rheonik range of Coriolis mass flowmeters can be attributed to the patented design features incorporating the dual Omega shaped tubes together with the mass beams and torsion rods. The Omega shape provides a half round active measurement section which keeps its form at any pressure. The mass bars then serve to decouple the active portion of the Omega shape from the process connections resulting in drastically reduced influence from vibration.
The mass bars and torsion rods work together to provide an harmonically swinging system that requires very little energy and at the same time provides stability and large amplitudes resulting in large signal to noise ratios. As a result, even the smallest flow rates can be measured reliably. Straight tube CMFs have a low signal to noise ratio. The Rheonik provides very high accuracy under real-life conditions.
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