ASME MFC-3Ma-2007 用孔板、喷咀和文杜利流量计测量管道中的流体流量.pdf

ASME MFC-3Ma–2007 Addenda to ASME MFC-3M–2004 Measurement of Fluid Flow in Pipes Using Orifice, Nozzle, and Venturi Three Park Avenue New York, NY 10016 AN AMERICAN NATIONAL STANDARD K0113A Date of Issuance March 24, 2008 ASME is the registered trademark of The American Society of Mechanical Engineers. This code or standard was developed under procedures accredited as meeting the criteria for American National Stan- dards. The Standards Committee that approved the code or standard was balanced to assure that individuals from com- petent and concerned interests have had an opportunity to participate. The proposed code or standard was made avail- able for public review and comment that provides an opportunity for additional public from industry, academia, regulatory agencies, and the public-at-large. ASME does not “approve,” “rate,” or “endorse” any item, construction, proprietary device, or activity. ASME does not take any position with respect to the validity of any patent rights asserted in connection with any items mentioned in this document, and does not undertake to insure anyone utilizing a standard against liability for infringe- ment of any applicable letters patent, nor assumes any such liability. Users of a code or standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, is entirely their own responsibility. Participation by federal agency representatives or persons affiliated with industry is not to be interpreted as gov- ernment or industry endorsement of this code or standard. ASME accepts responsibility for only those interpretations of this document issued in accordance with the established ASME procedures and policies, which precludes the issuance of interpretations by individuals. No part of this document may be reproduced in any , in an electronic retri system or otherwise, without the prior written permission of the publisher. The American Society of Mechanical Engineers Three Park Avenue, New York, NY 10016-5990 Copyright 2008 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All rights reserved Printed in U.S.A. 标准分享网 w w w .b z f x w .c o m 免费下载 MFC-3Ma2007 Following approval by the ASME MFC Standards Committee and ASME, and after public re- view, MFC-3Ma–2007 was approved by the American National Standards Institute on October 11, 2007. Addenda to the 2004 edition of ASME MFC-3M–2004 are issued in the of replacement pages. Revisions, additions, and deletions are incorporated directly into the affected pages. It is advis- able, however, that this page, the Addenda title and copyright pages, and all replaced pages be retained for reference. SUMMARY OF CHANGES This is the first Addenda to be published to ASME MFC-3M–2004. Replace or insert the pages listed. Changes given below are identified on the pages by a margin note, a07, placed next to the affected area. The pages not listed are the reverse sides of the listed pages and contain no changes. PageLocationChange 71-5.3.1Equations and nomenclature revised 91-6.4.1eMetric values for Dsmalland Dlargein subparas. 1 and 2 revised 11Table 1A-1In the fifth column, sixth and eighth entries are revised 14, 14.1Fig. 1C-1General Note added 202-4.1.5Revised 212-4.2.1b2Revised 22Fig. 2-3Note 1 revised 252-4.3.2.1In Eq. 2-5, values for U.S. Customary units revised 2-4.3.2.1c1 Penultimate paragraph added 2 Last paragraph revised 26, 26.12-5.1First sentence revised 27Table 2-3Sixth column head revised 282-5.2h1bThird line revised 292-5.2iFirst line revised 2-5.2i2Second line editorially revised 332-5.3.2.4Fifth line revised 342-5.3.3.1Last line of first paragraph revised 48.1NonmandatoryAdded Appendix 2B 493-1Last sentence of the third paragraph revised PageLocationChange 51–52.13-4.1.1Last sentence added 533-4.1.7.2Equation 3-8 revised in its entirety 553-4.2.5bLast sentence of the last paragraph revised 3-4.2.6.1New subpara. c added and subsequent subparagraph redesignated as d 563-4.2.7.2Equation 3-14 revised in its entirety 613-5.2h2bLast line of second paragraph revised 3-5.2iFirst line revised 63, 643-5.4cIn the last paragraph, “10” revised to read “6” 71, 724-4.2.8Second and third paragraphs revised 734-4.5.3cRevised 75, 764-5.2h1bLast sentence of the second paragraph revised 4-5.2i1 Last sentence revised 2 In Examples 1 and 2, fifth line revised 标准分享网 w w w .b z f x w .c o m 免费下载 w w w . b z f x w . c o m cient can occur over a period of time and can lead to values outside the uncertainties given in this Standard. c The primary device shall be manufactured from ma- terials for which the coefficient of expansion is known. 1-5.2 Nature of the Fluid a The fluid can be either compressible or incom- pressible. b The fluid shall be such that it can be considered as being physically and thermally homogeneous and single- phase. Colloidal solutions with a high degree of disper- sion can be considered to behave as single-phase fluids. c For measurement, it is necessary to know the den- sity and viscosity of the fluid at the working conditions. In the case of a compressible fluid it is also necessary to know the isentropic exponent of the fluid at the work- ing conditions. 1-5.3 Flow Conditions 1-5.3.1Pulsating Flow.This Standard does not provide for the measurement of pulsating flow see ISO 3313 for reference. The flow is considered sufficiently steady for this Standard to apply when SI Units 0.101-10 U.S. Customary Units 0.10 where phw time-mean value of the differential pressure prm hw root-mean-square value of p hw, the fluctuating component of the pressure prm hw can be measured accurately only by using a differential pressure sensor with sufficiently fast re- sponse see ISO 3313 for reference. Furthermore, the whole secondary system should con to the design recommendations specified in ASME MFC-8M. 1-5.3.2Phase Change of Metered Fluid. The uncer- tainties specified in this Standard are valid only when there is no change of phase through the primary device. Increasing the bore or throat of the primary element will reduce the differential pressure and may prevent a change of phase. For liquids, the pressure in the throat section must not fall below the vapor pressure of the liq- uid otherwise, cavitation will result. For gases, it is only necessary to calculate the temperature at the throat if the gas is in the vicinity of its dew point. The tem- perature in the throat can be calculated assuming an isentropic expansion from the upstream conditions the hw hw prm p upstream temperature may need to be calculated in ac- cordance with the Eq. 1-8 such that the fluid is in the single-phase region. 1-5.3.3Pressure Ratio. If the line fluid is a gas, the pressure ratio throat pressure to upstream pressure ra- tio, P2/P1 shall be between 0.80 and 1.00. If the fluid is a liquid, there is no limit to the pressure ratio, provided there is no phase change in the process fluid, and the primary element does not de or deflect excessively. For detailed ination, refer to Parts 2, 3, or 4 of this Standard as appropriate for specific primary devices. 1-6INSTALLATION REQUIREMENTS 1-6.1 General a The of measurement applies only to flu- ids flowing through a pipeline of circular cross section. b The pipe shall run full at the measurement section. c The primary device shall be fitted between two straight sections of cylindrical pipe of constant diame- ter and of specified minimum lengths in which there is no obstruction or branch connection other than those specified in Parts 2, 3, or 4 of this Standard as appro- priate for specific primary devices. The pipe is considered to be straight when the devi- ation from a straight line does not exceed 0.4 over its length. Flanges in the straight sections of pipe upstream and downstream of the primary device shall be at 90 deg 1/ 2deg to the pipe itself. The minimum straight lengths of pipe coning to the above requirement necessary for a particular installation vary with the type and specification of the primary device and the nature of the pipe fittings involved. d The pipe bore shall be circular over the entire min- imum length of straight pipe required. The cross section can be considered circular if it appears so by visual in- spection. The circularity of the outside of the pipe can be used as a guide, except in the immediate vicinity 2D of the primary device where special requirements shall apply according to the type of primary device used. Seamed pipe can be used, provided the internal weld bead is parallel to the pipe axis throughout the entire length of the pipe required to satisfy the installation re- quirements for the primary device being used. The seam must not be situated within 30 deg of any pressure tap used in conjunction with the primary device; no weld bead shall have a height greater than the permitted step in diameter according to the requirements of the pri- mary device used. If spirally wound pipe is used then it must be honed or machined smooth. e The interior of the pipe shall be clean at all times. Dirt that can readily detach from the pipe shall be re- moved. Any metallic pipe defects must be removed. The acceptable value of pipe roughness depends on the primary device. In each case there are limits on the value of the arithmetic mean deviation of the roughness MEASUREMENT OF FLUID FLOW IN PIPES USING ORIFICE, NOZZLE, AND VENTURIASME MFC-3Ma–2007 7 a07 w w w . b z f x w . c o m profile, Ra[see paras. 2-4.3.1, 3-4.1.2i, 3-4.1.6.1, 3-4.2.2f, 3-4.2.6.1, and 3-4.3.4.1 or para. 4-5.4.2. The internal sur- face roughness of the pipe shall be measured at ap- proximately the same axial locations as those used to determine and verify the pipe internal diameter. A min- imum of four roughness measurements shall be made to define the pipe internal surface roughness. In meas- uring Ra, an averaging-type surface roughness instru- ment with a cut-off value of not less than 0.75 mm 0.03 in. shall be used. The roughness can change with time as stated in para. 1-5.1b, and this should be taken into account in establishing the frequency of cleaning the pipe or checking the value of Ra. An approximate value of Racan be obtained by as- suming that Rais equal to k/, where k is the uni equivalent roughness as given in a Moody diagram. The value of k is given directly by a pressure loss test of a sam- ple length of pipe, using the Colebrook-White Equation given in para. 1-6.4.1e to calculate the value of k from the measured value of friction factor, . Approximate val- ues of k for different materials can also be obtained from the various tables given in reference literature, and Table 1B-1 gives values of k for a variety of materials. f The pipe can be provided with drain holes and/or vent holes to permit the removal of solid deposits and entrained fluids. There shall be no flow through either drain holes or vent holes, however, during the flow meas- urement process. In many custody transfer applications, drain holes or vent holes are explicitly prohibited. Drain and vent holes should not be located at the pri- mary device. When it is not possible to con to this requirement, the diameter of the vent or drain hole shall be less than 8 of the pipe inside diameter. The center- line of a pressure tap and the centerline of a drain or vent hole shall be offset from each other by at least 30 deg azimuthally i.e., in the plane perpendicular to the axis of the pipe and they shall be located no closer than 0.5D from each other. g Insulation of the meter may be required if the tem- perature difference between ambient conditions and the flowing fluid are significant given the desired measure- ment uncertainty. This is particularly important if the fluid being metered is near its critical point small tem- perature changes result in major density changes. It can be important at low flow rates, where heat transfer ef- fects can cause distorted temperature profiles, and a change in the mean temperature value from the upstream to the downstream side of the meter run, as well as strat- ification of temperature layers from top to bottom. A tem- perature difference between the upstream and the down- stream sides of the meter run can also occur. 1-6.2 Minimum Upstream and Downstream Straight Lengths of Pipe a The primary device shall be installed in the pipeline at a position such that the flow conditions im- mediately upstream of the primary device approximate those of swirl-free, fully developed pipe flow. Conditions meeting this requirement are specified in para. 1-6.3. b The required minimum upstream and down- stream straight lengths required for installation between various fittings and the primary device depend on the primary device. For some commonly used fittings as specified in paras. 2-5, 3-5, and 4-5 of this Standard, the minimum straight lengths of pipe indicated can be used. Flow conditioners, such as those described in para. 1-6.4, however, often permit the use of shorter upstream pipe lengths. Such flow conditioners must be installed upstream of the primary device for fittings not covered by paras. 2-5, 3-5, and 4-5 of this Standard, or where suf- ficient straight lengths to achieve the desired level of un- certainty are not available. 1-6.3 General Requirement for Flow Conditions at the Primary Device 1-6.3.1Requirement. If the specified conditions given in paras. 2-5, 3-5, and 4-5 of this Standard cannot be met, but the flow conditions immediately upstream of the primary device can be demonstrated to con to swirl-free fully developed flow as defined in paras. 1-6.3.2 and 1-6.3.3 over the entire Reynolds number range of the flow measurement application, the appli- cable sections of this Standard remain valid. 1-6.3.2Swirl-Free Conditions. Swirl-free conditions can be taken to exist when the swirl angle at all points over the pipe cross-section is less than 2 deg. 1-6.3.3Acceptable Flow Conditions. Acceptable ve- locity profile conditions can be presumed to exist when, at each point across the pipe cross-section, the ratio of the local axial velocity to the maximum axial velocity at the cross-section is within 5 of that which would be achieved in swirl-free flow at the same radial position at a cross-section located at the end of a very long over 100D straight length of similar pipe with fully devel- oped flow. 1-6.4 Flow Conditioners Some additional material regarding flow conditioners is given in Nonmandatory Appendix 1C. 1-6.4.1Compliance Testing a If a given flow conditioner passes the compliance tests outlined in paras. 1-6.4.1b to 1-6.4.1f for a par- ticular primary device, the flow conditioner can be used with the same type of primary device with any value of diameter ratio up to 0.67 downstrea