1、Date of Issue: March 2017 Affected Publication: API Manual of Petroleum Measurement Standards Chapter 14.3.2 “Orifice Metering of Natural Gas and Other Related Hydrocarbon FluidsConcentric, Square-edged Orifice MetersPart 2: Specification and Installation Requirements” Fifth Edition ERRATA Page 32,
2、the equation should read: ( )0.5 0.5224.38 10mF OD EL OD IDSV = +where L is the probe length (mm); Fm is the virtual mass factora constant to take account of the extra mass of the cylinder due to the fluid surrounding it and vibrating with it. For a gas, Fm = 1.0 and for water and other liquids, Fm
3、= 0.9; OD is the outside diameter of probe (mm); ID is the inside diameter of probe (mm); S is the Strouhal number, dependent on the Reynolds No. and shape of the cylinder, but can be taken as 0.4 for worst case or 0.2 as suggested by API MPMS Ch. 8. V is the velocity of fluid (m/sec); E is the modu
4、lus of elasticity of probe material (kg/cm2); is the density of probe material (kg/m3). Orifice Metering of Natural Gas and Other Related Hydrocarbon Fluids Concentric, Square-edged Orifice Meters Part 2: Specification and Installation Requirements AGA Report No. 3 Part 2 Manual of Petroleum Measure
5、ment Standards Chapter 14.3.2 American Gas Association 400 North Capitol Street, NW Washington, DC 20001 American Petroleum Institute 1220 L Street, NW Washington, DC 20005 FIFTH EDITION, MARCH 2016 ERRATA: MARCH 2017An American National Standard ANSI/API MPMS Ch. 14.3.2/AGA Report No. 3, Part 2 Spe
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23、a.org/knowledgecenter. Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW, Washington, DC 20005, standardsapi.org or Operations and Engineering Department, American Gas Association, 400 North Capitol Street, NW, Washington, DC 20001, http:/www
24、.aga.org/knowledgecenter. 5 Contents Page 1 Scope 1 1.1 General . 1 1.2 Construction and Installation Requirements 1 2 Normative References 1 3 Terms, Definitions, and Symbols 2 3.1 Definitions 2 3.2 Symbols/Nomenclature . 4 4 Orifice Plate Specifications . 6 4.1 General . 6 4.2 Orifice Plate Faces
25、6 4.3 Orifice Plate Bore Edge 8 4.4 Orifice Plate Bore Diameter (dm, dr) and Roundness . 8 4.5 Orifice Plate Bore Thickness (e) 10 4.6 Orifice Plate Thickness (E) . 10 4.7 Orifice Plate Bevel () . 13 5 Meter Tube Specifications . 13 5.1 Description 13 5.2 Orifice Plate Holders 17 5.3 Orifice Fitting
26、s Considerations . 18 5.4 Pressure Taps . 19 5.5 Flow Conditioners 21 6 Installation Requirements 23 6.1 General . 23 6.2 Orifice Plate 23 6.3 Meter Tube . 31 6.4 Acceptable Pulsation Environment . 31 6.5 Thermometer Wells 32 6.6 Insulation . 32 Annex A (informative) Research Projects and Tests Cond
27、ucted Between 1922 and 1999 . 33 Annex B (informative) Orifice Meter Inspection Guidelines 52 Annex C (normative) Specific Installation Calibration Test 56 Annex D (normative) Flow Conditioner Performance Test . 58 Annex E (normative) Maximum Allowable Orifice Plate Differential Pressure . 62 Figure
28、s 1 Symbols for Orifice Plate Dimensions . 6 2a Orifice Plate Departure from Flatness (Measured at Edge of Orifice Bore and Within Inside Pipe Diameter) . 7 2b Alternative Method for Determination of Orifice Plate Departure from Flatness (Departure from Flatness = h2 h1) 7 vi Contents Page 2c Maximu
29、m Orifice Plate Departure from Flatness . 7 3 Allowable Variations in Pressure Tap Hole Location . 19 4 1998 Uniform Concentric 19-Tube Bundle Flow Straightener 22 5 Eccentricity Measurements (Sample Method) 24 6 Orifice Meter Tube Layout for Flanged or Welded Inlet . 27 Tables 1 Roundness Tolerance
30、 for Orifice Plate Bore Diameter, dm9 2 Linear Coefficient of Thermal Expansion . 9 3 Orifice Plate Thickness and Maximum Allowable Differential Pressure Based on the Structural Limit 11 4 Example Meter Tube Internal DiameterRoundness Tolerances Within First Mean Meter Tube Diameter Upstream of Orif
31、ice Plate 16 5 Example Meter Tube Internal Diameter Roundness TolerancesAll Upstream Meter Tube Individual Internal Diameter Measurements . 17 6 Maximum Tolerance of Orifice Plate Bore Eccentricity (x) 25 7 Orifice Meter Installation Requirements Without a Flow Conditioner 28 8a Orifice Meter Instal
32、lation Requirements With 1998 Uniform Concentric 19-Tube Bundle Flow Straightener for Meter Tube Upstream Length of 17Di UL 1.000 0.0005 in. per in. of diameter a Use of diameters below 0.45 in. are not prohibited, but may result in uncertainties greater than those specified in API MPMS Ch.14.3.1/AG
33、A Report No. 3, Part 1. Table 2Linear Coefficient of Thermal Expansion Material Linear Coefficient of Thermal Expansion () USC (in./in. F) Metric Units (mm/mm C) Type 304/316 stainless steel c0.00000925 0.0000167 Type 304 stainless steel a0.00000961 0.0000173 Type 316 stainless steel a0.00000889 0.0
34、000160 Monel 400 a0.00000772 0.0000139 Carbon steel b0.00000620 0.0000112 NOTE For flowing temperature limits or other materials, refer to the American Society for Metals (ASM) Metals Handbook, Engineering Properties of Steel, and Handbook of Stainless Steels. a For flowing conditions between +32 F
35、and +212 F for stainless steels and +68 F and +212 F for Monel. b For flowing conditions between 7 F and +154 F, refer to API MPMS Ch. 12.2.1. c Type 304/316 stainless steel linear coefficient of thermal expansion is the average of the type 304 and type 316 stainless steel coefficients. NOTE Over a
36、temperature range from 32 F to 130 F the maximum difference in calculated flow between use of the 304/316 average coefficient and either the 304 or 316 coefficient is less than 0.005 % (50 ppm). 10 AGA REPORT NO. 3, PART 2/API MPMS CHAPTER 14.3.2 4.5 Orifice Plate Bore Thickness (e) The inside surfa
37、ce of the orifice plate bore shall be in the form of a constant-diameter cylinder having no defects, such as grooves, ridges, pits, or lumps, visible to the naked eye. The length of the cylinder is the orifice plate bore thickness (e). The minimum allowable orifice plate bore thickness (e) is define
38、d by e 0.01dr or e 0.005 in., whichever is larger. The maximum allowable value for the orifice plate bore thickness (e) is defined by e 0.02Dr or e 0.125dr, whichever is smaller, but e shall not be greater than the maximum allowable orifice plate thickness (E). When the orifice plate thickness (E) e
39、xceeds the orifice bore thickness (e), a bevel (see 4.7) is required on the downstream side of the orifice bore. Use of an unbeveled orifice plate with bore thickness (e) that exceeds the limits specified in Table 3 is outside of the scope of this standard. NOTE Existing orifice plates, whose edge t
40、hickness meets the value defined by e 0.7 in. of water/psia, where the P is in inches of water at 60 F and Pf is in psia) will result in expansion factor uncertainties in excess of 0.1 % (see 12.4.2 of API MPMS Ch.14.3.1/AGA Report No. 3, Part 1). Operators should be aware, for a given orifice plate
41、 size, that when there is a wide swing from high to low flows, significant measurement errors will occur during the low-flow period if the orifice plate remains unchanged. Generally, operation between 10 % and 90 % of the calibrated differential span is considered good practice. Rangeability can als
42、o be increased using todays digital (electronic) transmitters. The effects on the accuracy of transducers and/or transmitters used for wide range should be evaluated versus savings on installation cost. For the full range of orifice plate thicknesses, the maximum allowable orifice plate differential
43、 pressure can be obtained from Annex E. Higher differential pressures will result in higher meter-run gas velocities and higher permanent pressure losses. It is recommended that the gas velocities be evaluated on an individual installation basis for such things as noise, erosion, and thermowell vibr
44、ation. The meter run velocity is dependent on several different factors, and each individual user will have different practices and limits on velocity. The allowable maximum differential pressures, shown in Table 3, do not consider meter-run gas velocity. ORIFICE METERING, PART 2SPECIFICATION AND IN
45、STALLATION REQUIREMENTS 13 4.6.2 Permanent Pressure Drop The permanent pressure drop is significant because the energy has been lost to transport the fluid through the pipeline. Several technical books list the permanent pressure loss versus ratio for the concentric, square-edged, flange-tapped orif
46、ice meter. The permanent pressure loss P(1 2) Losses as a % of P 0.20 96 0.30 91 0.40 84 0.50 75 0.60 64 0.70 51 0.75 44 Examples: a) If the user chooses to use a of 0.30 at a P of 400 inches of H2O, then the permanent pressure loss would be approximately 91 % of 400 in. of H2O, which is about 364 i
47、n. of H2O or approximately 13 psi. b) If the user chooses to use a of 0.50 at a P of 100 in. of H2O, then the permanent pressure loss would be approximately 75 % of 100 in. of H2O, which is about 75 in. of H2O (about 3 psi). 4.7 Orifice Plate Bevel () The plate bevel angle () is defined as the angle
48、 between the bevel and the downstream face of the plate. The allowable value for the plate bevel angle () is 45 degrees 15 degrees. The surface of the plate bevel shall have no defects visible to the naked eye, such as grooves, ridges, pits, or lumps. If a bevel is required, its minimum dimension, (
49、E-e), measured along the axis of the bore shall not be less than 0.0625 (1/16) inch. 5 Meter Tube Specifications 5.1 Description The meter tube consists of the straight upstream pipe of the same diameter length UL of the installation Table 7 and Table 8, (see Figure 6), including the flow straightener/conditioner, if used; the orifice plate holder; and the similar downstream pipe (length DL of the installation Table 7, Table 8a, and Table 8bsee Figure 6) beyond the orifice plate. The upstream s
