Flowmeters, Coriolis

Mass Meters Mass flowmeters measure the rate of mass flow through a conduit. Examples include Coriolis flowmeters and thermal mass flowmeters. Coriolis flowmeters can measure fluid density simultaneously with mass flow rate. This permits calculation of volumetric flow rate as well. Section 8 includes brief descriptions of Coriolis and thermal mass flowmeters. 

Flow measurements using nonintrusive or low mechanical ac tion principles are desired, such as magnetic, vortex-shedding, or Coriolis-type flowmeters. Orifice plates are easy to use and reliable but have a limited range and may not be suitable for streams which are not totally clean. Rotameters with glass tubes should not be used. 

Coriolis flowmeter 267 Costich, E. W. 280,283,288.311 Coulson, J. M, 517, 565 Counter- and co-current flow, mass transfer 621 Countercurr ent contacting of phases 600 --flow 387... 

Coriolis Mass Flowmeter This type, described in Sec. 8, offers simultaneous direct measurement of both mass flow rate and fluid density. The Coriolis flowmeter is insensitive to upstream and downstream flow disturbances, but its performance is adversely affected by the presence of even a few percent of a gas when measuring a liquid flow. 

The principal classes of flow-measuring instruments used in the process industries are variable-head, variable-area, positive-displacement, and turbine instruments mass flowmeters vortex-shedding and ultrasonic flowmeters magnetic flowmeters and more recently, Coriolis mass flowmeters. Head meters are covered in detail in Sec. 5. 

Coriolis flowmeters can be used in both gas and liquid services, but are not suited for the measurement of their mixtures. The flow detection capability can range from 0 to 30,000 kg/min (0 to 65,000 lb/min), and these meters are available in sizes from 1 to 250 mm (0.05-10 in.). Their measurement error is 0.1% AF +/- zero offset which is about 0.01% within a 10 1 range. This error rises to 1% FS within a 100 1 range. This flowmeter can operate at temperatures from cryogenic to 450°C (850°F), and at pressures from atmospheric to 345 bar (5,000 psig). 

The measuring uncertainty for a 1 in. (DN25) Coriolis flowmeter. The maximum flow speed is 80 in./s (2 m/s), which is 20% of the maximum specified flow speed of the flowmeter. The curves show the specified error limits. 

The meter is not suited to measure gas-liquid mixtures or low-pressure gases and develops high pressure drops when the gas velocity is high. To keep the tubes full, they should be installed in vertical pipes with an upward flow direction. Besides their relatively high cost, CMF limitations also include their relatively small sizes (up to 150 mm, or 6 in.), their vibration sensitivity, and the limitation of standard designs to 205°C (400°F) and special ones to 425°C (800°F). The Coriolis-based mass flowmeters are popular in fuel cell, fuel flow, reactor feed, and in other applications where mass flowmeters are needed. 

Figure 5 gives the flow scheme of a feed oil system. A high pressure plunger pump feeds the reactor with oil at a pressure of about 75 bar. The mass-flow of feed oil is measured by three Coriolis-Flowmeters. The second pump is out of line. The feed oil flow is adjusted by pump speed which is variable in a range of 25 to 110 rpm. Two resonators are used for pulsation damping. 

The allowable pulsation in the plant depends for one thing on possible excitation of the mechanical structure and on the other on the installed Coriolis-Flowmeters (CFMs). 

Vetter, G., Notzon, S. Effect of pulsating flow on Coriolis mass flowmeters. Flow Measurement and Instumentation 5 (1994) 4, 263-273. 

Figure 6.122 Total view of a Coriolis mass flowmeter.

Figure 3 shows the test section and instrumentation. Ten wall temperatures on the tube external surface were measured with 0.5 mm diameter calibrated type E thermocouples electrically insulated from the aluminium. Fluid inlet and outlet temperatures were measured with 1 mm diameter calibrated type K thermocouples. Cah-bration was carried out with a Rosemount 162-CE platinum thermometer. Due to the high thermal conduchvity of the aluminium and the low thickness of the tube walls the measured temperature is very close to the wall temperature in contact with the fluid (the difference less than 0.01 K). The inlet fluid pressure was measured with a calibrated Rosemount type 11 absolute pressure sensor. Two calibrated differential pressure sensors measured the pressure loss through the test section. A Rosemount Micro-motion coriolis flowmeter was used to... 

Hoglen, W. and Valentine, J. Coriolis flowmeters improve hydrogen production Accurate steam-to-carbon ratio control provided efficient operation. Hydrocarbon Processing, 2007, 86 (8), 71. 

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