AGA GMM-4-2017 Gas Measurement Manual - Part 4 Gas Turbine Meter (XQ1701).pdf

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1、 Gas Measurement Manual Part 4 Turbine Meter (Revised February 2017) Prepared by the Transmission Measurement Committee GAS MEASUREMENT MANUAL PART 4 Turbine Meter (Revised) Prepared by the Transmission Measurement Committee Copyright 2017 American Gas Association All Rights Reserved Catalog # XQ170

2、1 i DISCLAIMER full name of the document; suggested revisions to the text of the document; the rationale for the suggested revisions; and permission to use the suggested revisions in an amended publication of the document. Copyright 2017, American Gas Association, All Rights Reserved. ii FOREWORD Th

3、is 2017 edition of Gas Measurement Manual, Part 4, Turbine Meter, is the revision of the 1985 edition. Substantial changes have been made to incorporate the latest industry knowledge on turbine meter technology. This document is primarily a training manual for engineers, technicians, and other perso

4、nnel who are new to gas flow measurement. This is not intended for use as a standard or for reference in contracts, tariff or other regulatory documents. Information on the topics covered by this publication may be available from other sources, e.g., manuals produced by turbine meter manufacturers,

5、which the reader may wish to consult for additional view or information not covered by this publication. Always consult with the particular meters manufacturer for guidance in cases where the information supplied by the manufacturer is not consistent with information presented in this manual and a p

6、rofessional in the field of expertise. Numerous problems and examples have been included to cover the many principles of Turbine meter measurement. They will help provide users of this document with a more complete understanding of these principles and how to incorporate them into real world applica

7、tions: Enhanced and Updated Turbine Meter Drawings reflecting Single Rotor Turbine Meters, and Dual Rotor Turbine Meters Examples of Manufacturers Calibration Documentation and Curves Example Problems for Computing Flow Example Equations for Meter Rangeability Example Problems for Minimum Flow Rate

8、and Rangeability Spin Time Test Example(s) and Procedures Example of Calibration Report Examples of K-Factors Established by Calibration Examples of Single K Factor Calibration Examples of Individual K Factor Calibration Examples of Meter Factor Example of Polynomial Curve Fit an Errors Example of L

9、inear Interpolation Curve Fit and Errors Example of Piecewise Curve Fitting Example of Final Meter Factor In this document the words shall, should and recommended are to be used to mean as follows: Shall means a requirement to conform to the specific task. Should and recommended are used synonymousl

10、y to indicate good practices to follow. iii ACKNOWLEDGEMENT The revision of this Gas Measurement Manual, Part 4, (GMM 4) was undertaken by a task group of the Transmission Measurement Committee (TMC). The task group was: Chaired by John R. Hand, Formerly with ConocoPhillips and Co-chaired by Ardis B

11、artle, APEX Measurement and Controls The members of the task group who contributed to its revision are: Russell Anderson, Chevron Pipeline Mike Bermel, Southern California Gas Company Jim Bowen, Sick, Inc. Joe Bronner, Formerly with Pacific Gas rather it is an indication that a measurement is more a

12、ccurate when it offers less error or uncertainty. Base Conditions: Defined pressure and temperature 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. Note: In the United S

13、tates for interstate custody transfer of natural gas, it is considered to be 14.73 psia and 60 F. Also see Standard Conditions. Change gears A set of mating gears in the output gear train of some turbine meters that can be changed during the calibration process. A gear combination can be selected, w

14、ith the appropriate ratio of teeth, to reduce the error in the mechanical output. Designer A company that designs metering facilities and specifies flow measurement equipment. Error The result of a measurement minus the reference value of the measurand. Note: Since the true value cannot be determine

15、d, in practice a conventional true or reference value is used, as determined by means of a suitable standard device. Error, Percent (Measured value reference value) / (reference value) x 100 Final meter factor A number developed either by averaging individual meter factors over the range of the mete

16、r operation or by weighting more heavily towards the meter factors over flow rates at which the meter is more likely to be used. The value is used as a single correction factor. Flow Meter, Reference A meter or measurement device of proven flow measurement uncertainty. K-factor Expressed in pulses p

17、er unit volume; also referred to as the “pulse factor”. It is associated with the electronic pulse output of the meter to produce a volume for an ancillary device (flow computer). If a meter has more than one electronic pulse output, then more than one K-factor may be appropriate. MAOP Maximum allow

18、able operating pressure. The maximum pressure at which a system or device may be operated in accordance with all applicable standards and regulations. 6 Manufacturer A company that designs, manufactures, sells and delivers flow meters. Maximum peak-to-peak error The difference between the largest an

19、d the smallest error values within a specified flow rate range. Measurand The quantity intended to be measured. Measurement cartridge A removable internal assembly, that includes measurement components, but excludes the meter body. Measurement Uncertainty A parameter, associated with the result of a

20、 measurement that characterizes the dispersion of the values that could reasonably be attributed to the measured quantity. The dispersion could include all components of uncertainty, including those arising from systematic effect. The parameter is typically expressed as a standard deviation (or a gi

21、ven multiple of it), defining the limits within which the measured value is expected to lie with a stated level of confidence. Meter factor A dimensionless numerical correction factor obtained by dividing the quantity of fluid measured by a standard, by the quantity indicated by the meter at any giv

22、en flow rate. Meter factors for individual flow rates can be combined to produce a single factor (final meter factor) to be used over the entire range of a meter. Operating range The range of ambient and process conditions over which the meter is designed to operate. Pressure drop The difference in

23、static pressure between two points in a flowing system. Qi The flow rate through the meter under a specific set of test or operating conditions. Qmax The maximum flow rate through the meter that can be measured within the specified performance requirements at a specific process condition. Qmin The m

24、inimum flow rate through the meter that can be measured within the specified performance requirement at a specific process condition. Qt The transition flow rate through the meter at which performance requirements may change. Rangeability The ratio of the maximum to minimum flow rates in the range o

25、ver which the meter meets specified error limit at a specified process condition. Also known as the turndown ratio. 7 Repeatability Closeness of the agreement between the results of successive measurements of the same measurand carried out under the same conditions of measurement. Notes: 1. These co

26、nditions are called repeatability conditions 2. Repeatability conditions include: The same measurement procedure The same observer The same measuring instrument used under the same conditions The same location Repetition over a short period of time 3. Repeatability may be expressed quantitatively in

27、 terms of the dispersion characteristics of the results. 4. A valid statement of repeatability requires specifications of the conditions of measurement (temperature, pressure, gas composition, etc.) that may affect the results. When a value of repeatability is given, a note shall be provided indicat

28、ing the specific calculations used to compute the dispersion characteristics. Reproducibility Closeness of agreement between the results of measurements of the same measurand carried out under changed conditions of measurement. Notes: 1. A valid statement of reproducibility requires specification of

29、 the conditions changed. 2. The changed conditions may include one or more of the following: principle of measurement method of measurement observer measuring instrument reference standard location conditions of use time 3. Reproducibility may be expressed quantitatively in terms of the dispersion c

30、haracteristics of the results. 4. A valid statement of reproducibility requires specification of the changed conditions of measurement that may affect the results. When a value of reproducibility is given, a note shall be provided indicating the specific calculations used to compute the dispersion c

31、haracteristics. 8 Rotor factor Coefficient(s) used with a manufacturer-specific calculation algorithm to compute the meter flow rate. Rotor factor(s) is/are typically associated with the electronic pulse output(s) from the rotor or each rotor in the case of a dual-rotor turbine meter. Standard Condi

32、tions Specific pressure and temperature conditions set by an authority for the measurement of fluid volume and other calculations. Note: The specific pressure and temperature conditions may vary from region to region, country to country and even organization to organization within the same country.

33、Typically, in the oil and gas industry in the USA, it is often interchangeably used with the base conditions. Also see Base Conditions. See the definition of base conditions. User The individual or company that uses a meter for measurement purposes. 9 Turbine Meter Designs 3.1 Single Rotor Turbine M

34、eters Gas Meter Design Figure 1A - Single Rotor Turbine Meter (Gas Design) Picture 4 Daniel & American Single Rotor Turbine Meters (Used with permission from Elster) 10 Schematics of axial flow single rotor turbine meters are shown in Figures 1A, 1B and 2. Gas entering the meter increases in velocit

35、y through the annular passage formed by the nose cone and the interior wall of the body. The movement of gas over the angled rotor blades imparts a force to the rotor, causing it to rotate. The ideal rotational speed is directly proportional to the flow rate. The actual rotational speed is a functio

36、n of the passageway size and shape, and the rotor design. It is also dependent upon the load that is imposed due to internal mechanical friction, fluid drag, external loading, and the gas density. Figure 1B - Single Rotor Angle Body Turbine Meter Figure 2 - Single Rotor Turbine Meter (Low Torque Des

37、ign) Inlet Outlet Body Nose Cone Rotor Electronic Pickup Annular Passage Tail Cone End Connection Inlet Nose Cone Body Rotor Electronic Pickup (optional) Mechanical or Electrical Readout Annular Passage 1 2 3 4 5 6 11 3.1.1 Low Torque (Liquid Meter) Design The basic designs of axial flow turbine met

38、ers differ significantly from liquid turbine meters due to density, viscosity and compressibility differences of the fluid being measured. The need to extract sufficient kinetic energy from the flow to provide the torque to overcome internal and external frictional losses result in the proportions o

39、f the nosecone and annular passages typical of those shown in Figures 1A & 1B. By reducing the diameter of the nose cone, figure 2, the annular passage will increase. This reduces the gas velocity through the annular passage resulting in lower torque generated by the rotor. Liquids being much denser

40、 compared to gas have no problems generating enough torque for these meters to operate. Turbine meter designs for gas flow measurement is similar in proportions to turbine meters for liquid flow measurement, as shown in Figure 2, have been successfully used for particular sizes and applications, (i.

41、e., sizes smaller than 4). For a given meter diameter size, a higher volume of gas can be measured for meters utilizing this liquid design compared to the standard gas design. The higher volume design increases the meters upper capacity at the expense of low-end sensitivity. Picture 5 Low Torque Tur

42、bine Meters (Used with permission from Elster) 3.2 Dual-Rotor Turbine Meters 3.2.1 Dual-Rotor Designs Schematics of various dual-rotor turbine meters are shown in Figures 3, 4, 5 and 6. The primary rotor or main metering rotor of each of these designs is basically the same as that of a single rotor

43、turbine meter as shown in Figure 1A. The blades of the primary rotor will typically have pitch angles in the range of 30 to 60 degrees. This rotor may have an output drive for a mechanical register or for an accessory device. Secondary rotor blades may have pitch angles as low as 3.5 degrees. Self-c

44、hecking turbine meters with secondary rotors (also known as sensing or slave rotor) are being utilized for gas measurement applications. Figures 3, 4, 5 & 6 are examples of such self-checking turbine meters. The secondary rotor of a dual rotor self-checking turbine meter provides additional informat

45、ion and intelligence that is not available from a single rotor turbine meter. By combining information from both rotors the dual rotor self-checking turbine meter can provide alarms and/or adjustments, either local or remote, to the metered volume to account for differences between calibration and f

46、lowing conditions, which might adversely affect the meters accuracy. (See 3.2.3) 12 Figure 3 - Independent Tandem Turbine Rotors separated by Flow Guides Figure 4 - Dual-Rotor Turbine with Fluid-Coupled Sensing Rotor Inlet Outlet Body Nose Cone Primary or Main Rotor Secondary or Sensing Rotor Electr

47、onic Pickups Readout Annular Passage Flow Guides 1 2 3 4 5 6 Inlet Outlet Body Nose Cone Electronic Pickups (Options) Annular Passage Main Rotor Sensing rotor Readout 1 2 3 4 5 6 13 Figure 5 - Fluid-Coupled Counter-Rotating Second Turbine Rotor Figure 6 - Dual-Rotor Turbine with Friction Reducing Se

48、condary Rotor Inlet Outlet Body Nose Cone Electronic Pickups Annular Passage Primary Rotor Secondary Rotor Inlet Outlet Body Nose Cone Main Rotor Secondary or Slave Rotor Electronic Pickups Annular Passage Piggy-Back Bearing Arrangement 14 Picture 6 Elster American & Sensus Dual Rotor Turbine Meters

49、 (Used with permission from both Elster & Sensus) 3.2.2 Secondary Rotor Designs The secondary rotor is placed downstream of the primary rotor, shown in Figures 3, 4, 5 and 6. It may be separated from the primary rotor and isolated from it by a flow conditioner placed between the two rotors (Figure 3). Some designs provide for fluid coupling of the secondary rotor to the primary rotor by positioning the rotors in close proximity to each other (Figures 4 and 5). In either c