https://www.repository.cam.ac.uk/bitstream/handle/1810/246007/Coriolis-draft-paper-V8.1-FMI-Larger-Fonts.pdf?sequence=1

Coriolis flowmeters: a review of developments over the past 20 years, and an assessment of the state of the art and likely future directions

A flowmeter is disclosed. The flowmeter includes a vibratable conduit, and a driver connected to the conduit that is operable to impart motion to the conduit. A sensor is connected to the conduit and is operable to sense the motion of the conduit and generate a sensor signal. A controller is connected to receive the sensor signal. The controller is operable to detect a single-phase flow condition and process the sensor signal using a first process during the single-phase flow condition to generate a validated mass-flow measurement. The controller is also operable to detect a two-phase flow condition and process the sensor signal using a second process during the two-phase flow condition to generate the validated mass-flow measurement.

Correcting for two-phase flow in a digital flowmeter

A mass flowmeter (1) based on the Coriolis principle is disclosed whose susceptibility to disturbances originating from the conduit, such as vibrations of the conduit or wide pressure variations of the fluid, and to other disturbances, such as impacts on the casing (11), is greatly reduced by mechanical means. It has a fluid inlet (113) and a fluid outlet (114) which are connected with the conduit via the casing; a support base (12) disposed within the casing and connected with the casing via at least one mechanical damping element (13, 14) which is located on a nodal line of vibration (19) of the support base; a single measuring tube which is bent in a plane parallel to the support base and ends in the fluid inlet (113) and the fluid outlet (114), a portion of said measuring tube to be vibrated in a direction perpendicular to said plane being fixed to the support base by fixing means (121, 122) located in the areas of opposite edges of the support base, and two connecting portions (152, 153) of said measuring tube extending from the respective fixing means to the fluid inlet and the fluid outlet, respectively; a vibrator (16); and at least one respective sensor (17, 18) disposed near each of the fixing means for sensing the vibrations of the tube portion.

Coriolis-type mass flow sensor with a single measuring tube

A method for determining pressure in an operating Coriolis effect mass flowmeter (10). The Coriolis flowmeter flow tubes (130, 130') are vibrated in both a bending mode (as is normal for measuring mass flow rate) and in a twisting mode. The ratio of the fundamental frequencies at which the flow tubes vibrate in each of the two vibration modes is proportional to the pressure within the flow tubes. In the preferred embodiment, a sum/difference method initially isolates the superposed sinusoids representing the fundamental frequencies of the two vibrational modes. Fast conjugate gradient (FCG) digital filters (512, 514) are then used to rapidly estimate the fundamental frequencies in each of the two vibration modes. The estimated frequencies are then used by filter chains including digital notch (518, 508) and band pass filters (506, 1520) as well as recursive maximum likelihood (RML) digital filter (510, 522) techniques to enhance the bending mode and twisting mode fundamental frequency estimates. The enhanced bending mode andtwisting mode frequency estimates are used to determine the pressure within the flow tubes as a function of the ratio of the two frequencies as well as to center the notch and band pass filter chains used to enhance the bending mode frequency of the two vibration sensor channels for mass flow rate computations. The pressureso determined may then be used to correct mass flow rate computations or for other pressure measurement purposes per se.

Method and apparatus for measuring pressure in a coriolis mass flowmeter

Drivers and sensors in Coriolis-type mass flowmeters are used to monitor and predict flowmeter failure modes due to mechanical deterioration during meter operation. The relative values of two different signals, e.g, resonant frequencies, associated with Coriolis flow conduit motion are monitored as an indicator of excessive mechanical deterioration and also used to compensate for shifts in meter factor. The noise spectrum of the sensor output is also monitored to indicate mechanical fatigue of the tubes. Energy loss in the vibrating tubes is monitored as an indication of fatigue to determine tube failure by determining the drive power needed to maintain constant velocity oscillation or measuring the decay rate of the drive signal when driver power is interrupted.

Method and apparatus for correcting for performance degrading factors in coriolistype mass flowmeter

Several Radial Mode Coriolis mass flow rate meter geometries and electronic circuits are described that may be made to be sensitive to pressure or density changes. In one embodiment, the meter comprises: (A) a flow conduit (1) for containing a fluid having a physical characteristic, the fluid (21) adapted to flow in the conduit at an unknown rate, (B) a drive circuit (16, 17) for creating a vibration in the flow conduit (1), the fluid (21) altering the vibration as a function of the physical characteristic and the flow rate, (C) a detector circuit (10-15) for measuring the altered vibration at a working point (38, 55) and producing a signal representing an uncompensated mass flow rate (M1) of the fluid and (D) a computation circuit for calculating a compensated mass flow rate (M2) of the fluid proportional to the uncompensated rate by 1/Φ1n, where Φ1 is a driven natural frequency of the flow conduit and n is a number chosen as a function of the working point, the compensated rate thereby reduced of effects of the physical characteristic. A unique mathematical algorithm is also described that allows for a much wider variety of design geometry while maintaining insensitivity to pressure or density without having to measure or compensate for either. In addition, a method is described that allows for the accurate measurement and compensation of both pressure and density.

Donald R. Cage

Papers

Coriolis mass flow rate meter having adjustable pressure and density sensitivity

Coriolis massendurchflussmesser mit einstellbarer druck und dichteempfindlichkeit