API MPMS 14.12 2017 pdf download.Manual of Petroleum Measurement Standards Chapter 14—Natural Gas Fluid Measurement Section 12—Measurement of Gas by Vortex Meters.
1 Scope This Standard addresses the following: a) provides generic information on full-bore vortex shedding flowmeters, including glossary, and sets of engineering equations useful in specifying performance; b) describes vortex shedding flowmeters in which alternating vortices are shed from one or more bluff bodies installed in a closed conduit; c) describes how the vortex shedding frequency is used to determine the velocity to infer the volume, mass, and/or energy flow rate and the total gas flow through the meter over a specific time interval; d) applies only to single phase gas flows in closed conduit that are steady or vary slowly in time. For fiscal measurement, the output of the flow rate shall be within the acceptable limits of steady state flow rate; e) describes the physical components of vortex shedding flowmeters and identifies need for inspection, certification, and material traceability; f) addresses the effect of gas properties, installation, and process conditions that may affect the measurement uncertainty and describes guidelines for reducing or eliminating their influences; g) defines the method for calculating uncertainty of the flow rate measurement; h) defines the meter output requirements and necessary information pertaining to the meter output for the purpose of fiscal measurement of gas; and i) provides calibration and/or performance verification guidance for the field application. 2 Normative References The following referenced documents are indispensable for the application of this document.
3 Terms, Definitions, Symbols, and Abbreviations 3.1 Terms and Definitions The following definitions are useful in describing the characteristics of vortex shedding flowmeters. 3.1.1 accuracy The closeness of agreement between a measured quantity value and a true quantity value of a measurand. 3.1.2 fade or pulse drop-off Under certain flowing conditions (i.e. below a minimum Reynolds number), vortex meters fail to shed or will shed vortices of insufficient strength to be detected by the meter electronics. 3.1.3 frequency output An output in the form of frequency, which varies as a function of the applied measurand (for example, angular speed and flow rate). 3.1.4 K-factor The number of pulses generated by the meter per gross unit volume. 3.1.5 laminar flow A smooth flow of fluid in which no cross flow of fluid particles occurs between adjacent stream lines. The transistion from smooth uniform laminar flow to turbulent flow generally occurs as the Reynolds number increases from about 2300 to 4000 or more. 3.1.6 linearity of a meter The ideal accuracy curve of a volume meter is a straight line denoting a constant meter factor. Meter linearity is expressed as the total range of deviation of the accuracy curve from such a straight line between the minimum and maximum recommended flow rates. 3.1.7 lubricity The measure of the reduction in friction and/or wear by a lubricant.
3.1.8 manufactured pulses Pulse outputs generated by transmitter electronics that are proportional to flow or some other parameter by means of analog or digital signal processing and might include some type of filtering. Manufactured pulses can have a delay that may lead to a bias error that should be considered during proving runs to ensure synchronization with prover. 3.1.9 nominal K-factor The number of pulses generated or electronically manufactured by the meter per indicated unit volume. 3.1.10 period jitter The small random variation that occurs in the vortex shedding period from one vortex cycle to another because vortex shedding is a result of a hydrodynamic instability, even at constant flow rates. 3.1.11 permanent pressure drop or permanent pressure loss The differential pressure between the inlet and downstream location of the meter after the pressure recovery at a given flow rate. The permanent pressure drop is a function of velocity through the meter, meter inside diameter and flowing fluid properties such as density and viscosity. 3.1.12 primary element for vortex meter The primary element that responds to the change in the variable (velocity) that is being monitored in the flow tube of a vortex meter is the shedder bar. 3.1.13 rangeability The capability of a meter or flow measuring device to operate between the minimum and maximum flow range within a specified uncertainty; expressed as the ratio of maximum flow to the minimum flow. See also 3.1.20. 3.1.14 repeatability Measurement precision under a set of repeatable conditions of measurement.