ASME MFC-6-2013 pdf download
ASME MFC-6-2013 pdf download.Measurement of Fluid Flow in Pipes Using Vortex Flowmeters.
1 sCoPe This Standard (a) describes the use of vortex fowmeters, including their physical components, principle of operation, instal- lation, performance, infuence factors, and calibration in a closed conduit running full for the measurement of volu- metric fow rate and volume fow total of single-phase liquids or gases, including vapors such as steam (b) describes the use of vortex fowmeters in combi- nation with one or more other process measurements for the inferential measurement of mass fow rate, mass fow total, base volumetric fow rate, base volume total, and heat fow metering (c) is limited to full-bore fowmeters and does not include the special case of insertion-type fowmeters 2 referenCes and related doCuMents Unless otherwise indicated, the latest issue of a refer- enced standard shall apply. ASME MFC-1M, Glossary of Terms Used in the Measurement of Fluid Flow in Pipes Publisher: The American Society of Mechanical Engineers (ASME), Two Park Avenue, New York, NY 10016- 5990; Order Department: 22 Law Drive, P.O. Box 2900, Fairfeld, NJ 07007-2900 (www.asme.org) IEC 60529, Degrees of Protection Provided by Enclosures (IP Code) Publisher: International Electrotechnical Commission (IEC), 3, rue de Varembé, Case Postale 131, CH-1211 Genève 20, Switzerland/Suisse (www.iec.ch) 3 terMinologY and sYMBols 3.1 defnitions from asMe MfC-1M used in this standard For the purposes of this Standard, the following def- nitions are particularly useful in describing the charac- teristics of vortex shedding fowmeters. ASME MFC-1M provides a more extensive collection of defnitions and symbols pertaining to the measurement of fuid fow in closed conduits. cavitation: the implosion of vapor bubbles formed after fashing when the local pressure rises above the vapor pressure of the liquid. fashing: the formation of vapor bubbles in a liquid when the local pressure falls to or below the vapor pressure of the liquid, often due to local lowering of pressure because of an increase in the liquid velocity. K factor: in pulses per unit volume, the ratio of the meter output in number of pulses to the corresponding total volume of fuid passing through the meter during a measured period. Variations in the K factor may be pre- sented as a function of either the meter bore Reynolds number or the fow rate of a specifc fuid at a specifc set of thermodynamic conditions (see Fig. 9.2-1). lowest local pressure: the lowest pressure found in the meter. This is the pressure of concern regarding fashing and cavitation. Some of the pressure is recovered down- stream of the meter.
5.1.2.2 digital transmitters. Digital transmitters use one or more microprocessors to process raw input signals and provide output signals and a user interface. These transmitters are often referred to as smart trans- mitters. Their use of microprocessors provides several advantages over analog transmitters. Because the input signals are processed digitally, these transmitters can analyze the signals using mathematical algorithms to determine installation quality, external interference, and noise. Based on this analysis, the transmitters may be able to digitally flter out spurious signals. The use of microprocessors and digital processing minimizes the effect of component drift that may occur in analog trans- mitters. Digital transmitters may also be able to compen- sate for changes in the meter K factor caused by changes in process temperature and pressure. Typical human interface is via a digital numeric or graphical display and buttons and optical or magnetic sensors to program parameters, or via a handheld com- municator. Digital transmitters are programmable for range and other parameters in user-selectable units and languages. This confguration is stored on the transmitter and may also be uploaded via the communication pro- tocol to other devices. Digital transmitters may also include the ability to program a low-fow cutoff below which the instrument either emits an error signal or holds the output to zero. Alternatively, at no-fow conditions, the digital transmit- ter may determine the low-fow cutoff by differentiating between signal and noise, and adjust the measurement threshold accordingly. Digital transmitters may be enabled with protocols that allow communication with other compatible instru- ments, communication devices, and control systems such as distributed control systems (DCS). Most digital transmitters include a programmable output range of 4 mA to 20 mA unless precluded by a communication protocol. They are also likely to include a programmable pulse or frequency output range. 5.1.2.3 Multivariable transmitters. Multivariable transmitters are digital transmitters equipped with mul- tiple inputs to the electronics to provide the temperature and pressure of the fuid that the meter is measuring. Multivariable transmitters perform a larger number of calculations than do typical digital transmitters. Vortex shedding fowmeters measure the volumetric fow rate. In many applications, the mass fow rate of the fuid is of interest. To calculate the mass fow rate from a vortex shedding meter’s volumetric fow reading, the fowing density of the fuid must be determined. The fowing den- sity can be calculated from the fowing temperature, pres- sure, and an equation of state for the specifc fuid.
