ASME MFC-16–2007 pdf download.Measurement of Liquid Flow in Closed Conduits With Electromagnetic Flowmeters.
1 SCOPE This Standard is applicable to industrial electromag- netic flowmeters and their application in the measure- ment of liquid flow. The electromagnetic flowmeters covered by this Standard utilize an alternating electrical current (AC) or pulsed direct-current (pulsed-DC) to generate a magnetic field in electrically conductive and electrically-homogeneous liquids or slurries flowing in a completely filled, closed conduit. This Standard specifically does not cover insertion- type electromagnetic flowmeters, meters used to mea- sure flow in partially filled pipe, or those used in surgi- cal, therapeutic, or other health and medical applications. Italso does notcover applications ofindus- trial flowmeters involving nonconductive liquids or highly conductive liquids (e.g., liquid metals). 2 REFERENCES All references are to the latest published edition of these standards. The following is a list of publications referenced in this Standard. ASME B16 Series, Standards for Valves, Fittings, Flanges, and Gaskets ASME MFC-1M, Glossary of Terms Used in the Measurement of Fluid Flow in Pipes Publisher: The American Society of Mechanical Engineers (ASME), Three Park Avenue, New York, NY 10016-5990; Order Department: 22 Law Drive, P.O. Box 2300, Fairfield, NJ 07007-2300 ISO 13359, Measurement of Conductive Liquid Flow in Closed Conduits — Flanged Electromagnetic Flowmeters — Overall Length Publisher: International Organization for Standardiza- tion (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Gene`ve 20, Switzerland/Suisse 3 DEFINITIONS AND SYMBOLS (a) Paragraph 3.1 lists definitions from ASME MFC-1M used in ASME MFC-16. (b) Paragraph 3.2 lists definitions specific to this Standard. (c) Paragraph 3.3 lists symbols used in this Standard (see Table 1).
3.1 Definitions From ASME MFC-1M accuracy: the degree of freedom from error; the degree of conformity of the indicated value to the true value of the measured quantity. precision: the closeness of agreement between the results obtained by applying the experimental procedure sev- eral times under prescribed conditions. The smaller the random part of the experimental errors that affect the results, the more precise is the procedure. rangeability (turndown): flowmeter rangeability is the ratio of the maximum to minimum flow rates or Reyn- olds number in the range over which the meter meets a specified uncertainty (accuracy). repeatability: the closeness of agreement among a series of results obtained with the same method on identical test material, under the same conditions (same operator, same apparatus, same laboratory, and short intervals of time). uncertainty (ofmeasurement): the range within which the true value of the measured quantity can be expected to lie with a specified probability and confidence level. 3.2 Definitions for ASME MFC-16 bias: the systematic errors (i.e., those that cannot be reduced by increasing the number of measurements taken under fixed flow conditions). flowmeterprimary: includes the flowtube, process connec- tions, electromagnetic coils, and electrodes. Flowmeter primary is also known by other names such as: flow- meter primary device, primary device, primary etc. flowmeter secondary: includes the electronic transmitter, measurement of the emf v , and in most cases the power for the electromagnet coils of the flowmeter primary. linearity: linearity refers to the constancy of the meter factor over a specified range, defined by either the pipe Reynolds number or the flow rate. meter factor: the number, determined by liquid calibra- tion, that enables the output flow signal to be related to the volumetric flow rate under defined reference con- ditions. 3.3 Symbols See Table 1.
4.2 Electrochemical Electromotive Force In addition to the flow-related electromotive force, emf v , an electrochemical electromotive force, emf c , is present between the electrodes. The emf c is an electro- chemical emfproduced in the flowmeter primary similar to that generated in a battery. It can be similar in magni- tude to emf v and changes slowly. In order to reduce emf c , which would be a measurement bias, an alternating electromagnetic field is used. There exist a number of variations of the basic AC and DC fields shown in this Standard. See para. A-2.1 for additional information. This electrochemical voltage, which varies slowly in time, is substantially reduced in magnitude by utilizing an alternating electromagnetic field. The manner in which the electromagnetic field is var- ied includes the following: (a) AC — field is varied in a sinusoidal fashion [see Fig. 3, illustration (a)] (b) DC — field is varied in a stepwise fashion [see Fig. 3, illustrations (b) and (c)] 4.3 Types of Electrodes An alternating electromagnetic field generates an alternating emf v . Two types of electrodes can be used with an alternating electromagnetic field (a) wetted electrodes that protrude through the pipe wall/liner into the flow stream [see Fig. 4, illustration (a)] (b) nonwetted (capacitive) electrodes located behind or within the tube wall/liner [see Fig. 4, illustration (b)]