Electromagnetic flow meters

Electromagnetic flow meters ate avadable with various liner and electrode materials. Liner and electrode selection is governed by the corrosion characteristics of the Hquid. Eor corrosive chemicals, fluoropolymer or ceramic liners and noble metal electrodes are commonly used polyurethane or mbber and stainless steel electrodes are often used for abrasive slurries. Some fluids tend to form an insulating coating on the electrodes introducing errors or loss of signal. To overcome this problem, specially shaped electrodes are avadable that extend into the flow stream and tend to self-clean. In another approach, the electrodes are periodically vibrated at ultrasonic frequencies. 

Electromagnetic flow meters ate available in essentially all pipe si2es, ie, 1 mm to 3 m, and provide measurement accuracy of 1% of rate or better over wide ranges. The meters are obstmctionless, have no moving parts, and are extremely mgged. Pressure loss is that of an equivalent section of pipe. 

Because of these characteristics electromagnetic flow meters have been widely appHed to the measurement of difficult Hquids such as raw sewage and wastewater flows, paper pulp slurries, viscous polymer solutions, mining slurries, milk, and pharmaceuticals. They ate also used in less demanding apphcations such as the measurement of large domestic water volumes. 

Several special forms of electromagnetic flow meters have been developed. A d-c field version is used for Hquid metals such as sodium or mercury. Pitot and probe versions provide low cost measurements within large conduits. Another design combines a level sensor and an electromagnetic meter to provide an indication of flow within partially full conduits such as sewer lines. 

Measurement based on electromagnetic effect Experimental investigation has been done to examine the use of an electromagnetic flow meter to measure the continu-... 

The basic construction and theory of operation of rotameters, nutating disks, anemometers, electromagnetic flow meters, and ultrasonic flow equipment are summarized below. 

With regard to multiphase flow measurement, two of the most commonly used flow meter devices in industry are the Coriolis flow meter and electromagnetic flow meter. The Coriolis flow meter is widely used owing to its high accuracy (Tavoularis, 2005) but it assumes... 

Rote et al. (1993, 1994) used a carotid thrombosis model in dogs. A calibrated electromagnetic flow meter was placed on each common carotid artery proximal to both the point of insertion of an intravascular electrode and a mechanical constrictor. The external constrictor was adjusted with a screw until the pulsatile flow pattern decreased by 25 % without altering the mean blood flow. Electrolytic injury to the intimal surface was accomplished with the use of an intravascular electrode composed of a Teflon-insulated silver-coated copper wire connected to the positive pole of a 9-V nickel-cadmium battery in series with a 250000 ohm variable resistor. The cathode was connected to a subcutaneous site. Injury was initiated in the right carotid artery by application of a 150 xA continuous pulse anodal direct current to the intimal surface of the vessel for a maximum duration of 3 h or for 30 min beyond the time of complete vessel occlusion as determined by the blood flow recording. Upon completion of the study on the right carotid, the procedure for induction of vessel wall injury was repeated on the left carotid artery after administration of the test drug. 

FLOW INDICATION. An electromagnetic flow meter is used on the primary heat-removal system of the submerged EBR-II reactor model. Figure 11 schematically shows the manner of jacketing the two electrodes of the flowmeter to bring them through the sodium and top of the reactor tank. The permanent magnet is surrounded by sodium. The electrodes are canned with a thin stainless steel sleeve concentric with the 4-inch sodium pipe. Inside the stainless steel can and sand-... 

Determination of caustic production rate using a flow meter. This is the most convenient method, but it is not always favored because of the lack of certification of calibration. The accuracy of electromagnetic flow meters and Coriolis mass flow meters is very high (c. 0.5%) and reliable results have been obtained consistent with other methods of measurement. Both types can be used to integrate flow. The Coriolis type is particularly advantageous, as it does not require separate density determinations. 

Thereafter many physiologists attempted to measure blood flow through the stomach by the simple means of measuring blood collected from a vessel similar to Burton-Opitz s vena gastrica. Burton-Opitz had not used an anticoagulant, and his experiments terminated when blood clotted in his cannula, but later observers used hirudin, or eventually heparin, so that they could return the blood they collected to the animal. When electromagnetic flow meters became available, they too were used, but nothing of any importance was learned. ... 

At the same time that Jacobson was doing the work just described, he and two other colleagues prepared a dog with a Heidenhain pouch supplied by a single artery around which they placed an electromagnetic flow meter and a hydraulic occluder. Flow rose under histamine stimulation and fell under pitressin inhibition. Using aminopyrine clearance as a measure of mucosal flow, Jacobson found that with increasing doses of histamine both secretion and aminopyrine clearance rose, but that there was no correlation between mucosal flow as measured by aminopyrine clearance and total flow. During brisk secretion, mucosal flow was 25 times the secretory rate. ... 

There is reason to believe that some published data are consistent with our observations. Of special note is the study by Stein et al. using a catheter tip electromagnetic flow meter placed inside the coronary sinus of intact dogs. They demonstrate the maximum outflow to occur in late systole or even early diastole in some dogs. If nothing else, these data suggest that there is considerable variability from dog to dog. 

Rotameter Ultrasonic type Turbine flow meter Electromagnetic flow meter Good for upstream flow measurements Used in conjunction with variable inductance sensor Good for very high flow rates Can be used for both upstream and downstream flow measurements Not suited for fluids containing abrasive particles Relationship between flow rate and angular velocity is linear Least intrusive as it is noncontact type Can be used with fluids that are corrosive, contaminated, etc. The fluid has to be electrically conductive... 

Electromagnetic flow meters and level gauges, etc. were tested for calibration with actual flowing sodium before delivery to the site. 

Wang JZ, Lucas GP, Han GY (2007) A numerictd approtich to the determination of electromagnetic flow meter weight functions. Meas Sci Technol 18 548-554... 

Fuel flows upward through the reactor core and into the degasser. From tlicfi. the flow goes down into the sump tank iud back into the reactor iiilci. The fuel is pumped elcctromagnetically and flow is measured by an oi iiici or an electromagnetic flow meter. 

In research reactors that use liquid metal coolant, flow can be measured either by use or an electromagnetic flow meter or by an ultrasonic flow meter. The electromagnetic flow meter generates a voltage proportional to the coolant flow, and the ultrasonic flow meter deduce the flow by measuring the sound transmission time between the transmitting and receiving rod pairs. The accuracy of measurement in both cases is around 10%. 

The temperature distribution in the loop is measured with chromel-alumel thermocouples and two Pt-100 temperature sensors for reference measurements. Absolute pressure is measured at the top of the riser and at the inlet of the core. The liquid level in the steam dome is measured with a differential pressure sensor. The differential pressure over the friction settings of the individual channels is a measure for the flow distribution over the coolant channels and bypass channels. The total flow in the loop is measured at 2 different positions with electromagnetic flow meters. The void fraction at a given height can be measured with gamma transmission techniques. At a fixed height at the top of the riser the radial void distribution is measured with a wire-mesh sensor, which measures the conduction of the two-phase mixture on a two-dimensional grid. Furthermore, laser doppler anemometry is used to study the local liquid velocity in the core or in the riser. 

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