1、 AGA Report No. 11 API MPMS Chapter 14.9 Measurement of Natural Gas by Coriolis Meter Prepared by Transmission Measurement Committee Second Edition, February 2013 AGA Report No. 11 API MPMS Chapter 14.9 Measurement of Natural Gas by Coriolis Meter Prepared by Transmission Measurement Committee Secon
2、d Edition, February 2013 Copyright 2013 American Gas Association All Rights Reserved Catalog # XQ1301 ii iii DISCLAIMER AND COPYRIGHT The American Gas Associations (AGA) Operations and Engineering Section provides a forum for industry experts to bring their collective knowledge together to improve t
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14、Reserved. iv FOREWORD This report has been written in the form of a performance-based specification. If this performance-based specification is used, Coriolis meters shall meet or exceed the function, accuracy, and testing requirements specified in this report and designers shall follow the applicab
15、le installation recommendations. This report is split into two distinct sections the main body of the report and a series of appendices. The main body should be considered normative as it describes working practice when applying and using Coriolis meters to measure natural gas flow. The appendices a
16、re informative and contain additional material, background and examples of how Coriolis meters are installed and operated. Methods for verifying a meters accuracy and/or applying a Flow Weighted Mean Error (FWME) correction factor to minimize the measurement uncertainty are contained in Appendix A,
17、“Coriolis Gas Flow Meter Calibration Issues.” Depending on the design, it may be necessary to flow-calibrate each meter on a gas similar to that expected in service. In order to guide the designer in the specification of a Coriolis meter, Appendix B, “Coriolis Meter Data Sheet,” has been provided. A
18、s a reference for background information on Coriolis natural gas metering, Appendix C, “AGA Engineering Technical Note, XQ0112, Coriolis Flow Measurement for Natural Gas Applications,” is provided. Due to the unique principle of operation and atypical performance characteristics of Coriolis mass flo
19、w meters, in comparison to volumetric flow meters, readers who are not familiar with the technology are encouraged to read the Appendix C prior to applying the general concepts and guidelines of this report. This report offers general criteria for the measurement of natural gas by Coriolis meters. I
20、t is the cumulative result of years of experience of many individuals and organizations acquainted with measuring gas flow rate and/or the practical use of Coriolis meters for gas measurement. Changes to this report may become necessary from time to time. v ACKNOWLEDGEMENTS The revision work of this
21、 report was undertaken by a task group the Transmission Measurement Committee (TMC). The task group was chaired by Angela Floyd who was with ConocoPhillips during the development and finalization of this report. Angela was supported by the vice chair, Karl Stappert with Micro Motion. A special subco
22、mmittee of the task group was formed later to assemble additional technical information, compose the drafts of the revised report for balloting and finally resolve the ballot comments and prepare the final report. The members of the special subcommittee who devoted an extensive amount of their time
23、and deserve special thanks are Kerry Checkwitch, Spectra Energy Transmission Craig Chester, Williams Gas P/L John Daly, GE Sensing Robert DeBoom, Consultant Robert Fallwell, TransCanada P/L Ron Gibson, ONEOK, Inc. Terry Grimley, Southwest Research Institute (SwRI) John Hand, Spectra Energy Transmiss
24、ion Michael Keilty, Endress + Hauser Flowtec AG Allen Knack, Consumers Energy Brad Massey, Southern Star Central Gas P/L Paul LaNasa, CPL and Associates Stephanie Lane, Micro Motion, Inc. Dannie Mercer, Atmos Energy Corporation Gary McCargar, ONEOK, Inc. Bill Morrow, Telvent Mark Pelkey, National Fu
25、el Gas Supply Corporation Dan Rebman, Universal Ensco Don Sextro, Targa Resources, Inc. Martin Schlebach, Daniel Measurement and Control, Inc. Tushar Shah, Eagle Research Corp. James N. Witte, El Paso Pipeline Group AGA acknowledges the contributions of the above individuals and thanks them for thei
26、r time and effort in getting this document revised. Christina Sames Ali Quraishi Vice President Director Operations and Engineering Operations and Engineering vi TABLE OF CONTENTS DISCLAIMER AND COPYRIGHT III FOREWORD IV ACKNOWLEDGEMENTS . V 1 INTRODUCTION 1 1.1 SCOPE 1 1.2 PRINCIPLE OF MEASUREMENT
27、. 1 2 TERMINOLOGY, UNITS, DEFINITIONS i.e., they are bidirectional. The inertial force that results is proportional to the mass flow rate. The mass flow rate, thus determined, is divided by the gas base density to obtain the base volume flow rate. The flowing density of a gas as indicated by a Corio
28、lis meter is not of sufficient accuracy to be used for the purpose of calculating flowing volume from flowing mass of the gas and shall not be used for this purpose. 2 TERMINOLOGY, UNITS, DEFINITIONS rather it is an indication that a measurement is more accurate when it offers less error or uncertai
29、nty. Allowable Pressure The differential pressure available for consumption by the metering Drop module, as specified by the designer. Ancillary Device A device intended to perform a particular function, directly involved in elaborating, transmitting or displaying measurement results. Application Ga
30、s A gas of known physical properties which will be measured. Base Conditions Defined pressure and temperature conditions used in the custody transfer measurement of fluid volume and other calculations. Base conditions may be defined by regulation, contract, local conditions or organizational needs.
31、In the United States for inter-state custody transfer of natural gas, it is considered to be 60 F and 14.73 psia. Baseline Point Clearly defined starting point (point of departure) from where implementation begins Calibration The process of determining, under specified conditions, the relationship b
32、etween the output (or response) of a device to the value of a traceable reference standard with documented uncertainties. The relationship may be expressed by a statement, calibration function, calibration diagram, calibration curve, or calibration table. In some cases, it may consist of an additive
33、 or multiplicative correction of the indication with associated measurement uncertainty. Any adjustment to the device, if performed, 3 following a calibration, requires a verification against the reference standard. Any adjustment to the device, if performed, following a calibration requires a verif
34、ication against the reference standard. Calibration Factor Manufacturer flow calibration scalars that are applied to the meters output(s) value to adjust the output(s) value(s) to the as-built performance (i.e. zero, span, linearity, etc.) of the sensor. Confidence Level The degree of confidence, ex
35、pressed as a percentage, that the true value lies within the stated uncertainty. For example: A proper uncertainty statement would read: “mQ=500 lb/h 1.0% at a 95% level of confidence.“ This means that 95 out of every 100 observations are between 495 and 505 lb/h. Compressibility factor A factor cal
36、culated by taking the ratio of the actual volume of a given mass of gas at a specified temperature and pressure to its volume calculated from the ideal gas law at the same conditions. Cross Talk Vibration interaction of two Coriolis sensors that are mechanically connected and whose resonant frequenc
37、ies are identical. Discrete Error Value An estimate of error for an individual measurement, expressed in “percent of reading” or in engineering units. Drift A slow change of a metrological characteristic of a measuring instrument. Drive Signal An electrical signal produced by the transmitter to init
38、iate and maintain cyclic vibration of the sensor (measuring transducer) flow tube(s). Error The difference between a measured value and the true value of the measured quantity. (Note: Since the true value cannot be determined, in practice a conventional true or reference value is used, as determined
39、 by means of a suitable standard device.) Flow Pressure Effect The effect on accuracy when measuring mass flow at an operating pressure that differs from the calibration pressure Flow Pressure Effect A factor that adjusts mass flow for operating line pressure. Compensation Factor Flow Weighted Mean
40、The calculation of the FWME of a meter from actual flow test data is a Error ( FWME) method of calibrating a meter when only a single correction factor is applied to the meter output. FWME is only one of many techniques for adjustment of a Coriolis meter calibration to minimize the flow measurement
41、uncertainty of the meter. Note: FWME is calculated per Equation A.1 in Appendix A. Influence Quantity A quantity that is not the measured quantity but that affects the result of the measurement. Installation Effect Any difference in performance of a component or the measuring system arising between
42、the calibration under ideal conditions and actual conditions of use. This difference may be caused by different flow 4 conditions due to velocity profile and perturbations, or by different working regimes (pulsation, intermittent flow, alternating flow, vibrations, etc.). Maximum The largest allowab
43、le difference between the upper-most error point and Peak-to-Peak Error the lower-most error point as shown in Figure 6.1 and Section 6.1. This applies to all error values in the flow rate range between tQand maxQ. Maximum permissible The extreme error of a meters indicated value in percentage of th
44、e Error (MPE) reference value with which it is compared. (see Section 6.1). Mean Error The arithmetic mean of all the observed errors or data points for a given flow rate. Measuring System A system that includes the metering module and all the ancillary devices. Measuring Transducer A device that pr
45、ovides an output quantity having a determined relationship to the input quantity. Measurement Parameter associated with the result of a measurement that Uncertainty characterizes the dispersion of the values that could reasonably be attributed to the measured quantity. The dispersion could include a
46、ll components of uncertainty including those arising from systematic effect. The parameter is typically expressed as a standard deviation (or a given multiple of it), defining the limits within which the measured value is expected to lie with a stated level of confidence. Meter A measurement instrum
47、ent comprised of the sensor, which includes the flow tube(s) and measuring transducers, and the transmitter intended to measure continuously, memorize and display the volume or mass of gas passing through the sensor at metering conditions. Meter Sensor Mechanical assembly consisting of vibrating flo
48、w tube(s), drive system, flow tube position sensors, process connections/flanges, flow manifolds, supporting structure, and housing Metering Conditions The conditions of the gas, at the point of measurement, where the flow rate is measured, (temperature, pressure, composition, and flow rate of the m
49、easured gas). Metering Module The subassembly of a measuring system, which includes the sensor and all other devices (i.e., flow conditioners, straight pipe and/or metering tubes) required to ensure correct measurement of the measuring systems gas circuit. MUT Acronym for “Meter Under Test.” No Flow Cut-Off A flow rate below which any indicated flow by the meter is considered to be invalid and indicated flow output is set to zero. (Historically referred to as “low flow cut-off.”) Operating Range The range
