BS 1042-1.4-1992 封闭管道内液体流量的测量.第1部分压差器件.第4节第1和2节所述器件的使用指南.pdf

BRITISH STANDARD BS 1042-1.4 1992 Incorporating Amendment No. 1 Measurement of fluid flow in closed conduits Part 1 Pressure differential devices Section 1.4 Guide to the use of devices specified in Sections 1.1 and 1.2 Licensed Copy AUB User, na, Sat Jul 07 124900 GMT0000 2007, Uncontrolled Copy, c BSI BS 1042-1.41992 This British Standard, having been prepared under the direction of the Industrial-process Measurement and Control Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 31 March 1992 BSI 12-1998 First published March 1984 Second edition March 1992 The following BSI references relate to the work on this standard Committee reference PCL/2 Special announcement in BSI News, September 1991 ISBN 0 580 20404 9 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Industrial-process Measurement and Control Standards Policy Committee PCL/- to Technical Committee PCL/2, upon which the following bodies were represented British Compressed Air Society British Gas plc Department of Energy Gas and Oil Measurement Branch Department of Trade and Industry National Engineering Laboratory Electricity Industry in United Kingdom Energy Industries Council GAMBICA BEAMA Ltd. Institute of Measurement and Control Institute of Petroleum Institute of Trading Standards Administration Institution of Gas Engineers Institution of Mechanical Engineers Society of British Gas Industries Water Services Association of England and Wales The following bodies were also represented in the drafting of the standard, through subcommittees and panels Engineering Equipment and Materials Users’ Association Institution of Water and Environmental Management United Kingdom Offshore Operators’ Association Amendments issued since publication Amd. No.DateComments 8154June 1994Indicated by a sideline in the margin Licensed Copy AUB User, na, Sat Jul 07 124900 GMT0000 2007, Uncontrolled Copy, c BSI w w w . b z f x w . c o m BS 1042-1.41992 BSI 12-1998i Contents Page Committees responsibleInside front cover Foreword ii Section 1. General 1Scope1 2 Symbols 1 Section 2. Calculations 3General 2 4Ination required 2 5Basic equations 3 6Calculation of orifice or throat diameter3 7Calculation of rate of flow10 Section 3. Physical data 8Properties12 9Density of fluid12 10Viscosity of fluid14 11Isentropic exponent14 Section 4. Additional ination on measurements and on pulsating and swirling flow 12Measurements15 13Pulsating flow20 14Swirling flow23 Appendix A References for physical data24 Index25 Figure 1 Possible locations of density meters17 Figure 2 Multiplying factors for thermal expansion19 Figure 3 Damping pulsations in gas flow22 Figure 4 Damping pulsations in liquid flow22 Table 1 Symbols1 Table 2 Approximate values of CEb2 for square-edged orifice plates with corner, D, D/2 or flange taps as appropriate5 Table 3 Approximate values of CEb2 for ISA 1932 nozzles, and rough cast, machined and rough welded convergent venturi tubes6 Table 4 Approximate values of CEb2 for long radius nozzles7 Table 5 Approximate values of CEb2 for quarter circle orifice plates8 Table 6 Approximate values of CEb2 for eccentric orifice plates8 Table 7 Physical properties of selected liquids12 Table 8 Physical properties of selected gases13 Licensed Copy AUB User, na, Sat Jul 07 124900 GMT0000 2007, Uncontrolled Copy, c BSI w w w . b z f x w . c o m BS 1042-1.41992 ii BSI 12-1998 Foreword This Section of BS 1042 has been prepared under the direction of the Industrial-process Measurement and Control Standards Policy Committee. It supersedes BS 1042-1.41984, which is withdrawn. This is Section 1.4 of a series of Sections of BS 1042 on the measurement of fluid flow in closed conduits, as follows Section 1.1 Specification for square-edged orifice plates, nozzles and venturi tubes in circular cross section conduits running full Section 1.2 Specification for square-edged orifice plates and nozzles with drain holes, in pipes below 50 mm diameter, as inlet and outlet devices and other orifice plates Section 1.3 of measurement of gas flow by means of critical flow Venturi nozzles. Section 1.5 Guide to the effect of departure from the conditions specified in Section 1.1 Section 1.1 specifies the geometry and of use of orifice plates, nozzles and Venturi tubes inserted in conduit running full, to measure the flowrate of the fluid in the conduit. It is technically equivalent to ISO 51671980 published by the International Organization for Standardization ISO. It should be noted that guidance on the effects of departure from the conditions specified in BS 1042-1.1 can be found in BS 1042-1.51987. An index to Sections 1.1, 1.2 and 1.4 is provided in this Section, to facilitate the rapid cross-referencing of subject matter. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 33 and a back cover. This standard has been updated see copyright date and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy AUB User, na, Sat Jul 07 124900 GMT0000 2007, Uncontrolled Copy, c BSI w w w . b z f x w . c o m BS 1042-1.41992 BSI 12-19981 Section 1. General 1 Scope This Section of BS 1042 provides sample calculations, physical data and other additional ination for using the pressure differential devices specified in BS 1042-1.1 and BS 1042-1.2. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Symbols The symbols used in this standard are given in Table 1. Table 1 Symbols SymbolRepresented quantityDimensions M mass L length T time u temperature SI unit A Cross-sectional area L2 m2 C Coefficient of discharge, dimensionless d Diameter of orifice or throat of primary device at operating conditions L m D Upstream internal pipe diameter at operating conditions L m E Velocity of approach factor, dimensionless FA, FBCorrection factors dimensionless k Uni equivalent roughness L m p Static pressure of the fluid ML–1T –2 Pa qm Mass flowrate MT –1 kg/s qv Volume flowrate L3T –1 m3/s ReReynolds number dimensionless ReD, Red Reynolds number referred to D or d dimensionless t Temperature of the fluid u C X Acoustic ratio, dimensionless a Flow coefficient dimensionless b Diameter ratio, dimensionless Dp Differential pressure ML –1T–2 Pa Expansibility expansion factor dimensionless k Isentropic exponent dimensionless mDynamic viscosity of the fluid ML–1T –1 Pas y Kinematic viscosity of the fluid, L2T –1 m2/s r Density of the fluid ML–3kg/m3 t Pressure ratio, dimensionless NOTE 1Other symbols used in this standard are defined at their place of use. NOTE 2Some of the symbols used in this standard are different from those used in BS 1042-1.1. NOTE 3Subscript 1 refers to the cross section at the plane of the upstream pressure tapping. Subscript 2 refers to the cross section at the plane of the downstream pressure tapping. C α E ----- - E1β4– c–    X p∆ Pik -------- β d D ---- - υ ρ --- τ p2 p1 ----- - Licensed Copy AUB User, na, Sat Jul 07 124900 GMT0000 2007, Uncontrolled Copy, c BSI w w w . b z f x w . c o m BS 1042-1.41992 2 BSI 12-1998 Section 2. Calculations 3 General In clauses 4 to 7, typical design calculations for the design of orifice plates, nozzles, venturi tubes and venturi nozzles are given. The principal design calculations that are commonly required for pressure differential devices are a assessment of the differential pressure and calculation of the diameter of an orifice or nozzle or venturi throat for a stated flow of a given fluid in a given pipe at specified conditions of pressure and temperature; b calculation of the differential pressure for a stated flow of a given fluid at known temperature and pressure, for a pressure differential device and pipe of known diameter; c calculation of the flowrate, given the fluid, pressure differential device diameter and pipe diameter, differential pressure and fluid pressure and temperature; d calculation of the overall uncertainty of the installation for a given flowrate. Items a and d are particularly relevant to the design of a new installation whereas b and c are applicable to working installations. The of calculating the overall uncertainty is described in clause 11 of BS 1042-1.11992. The precise sequence of the calculation will depend upon the ination required and on the choice of pressure differential device. The calculations are based on the assumption that the size of the pipe needed to carry the fluid is known. 4 Ination required 4.1 General The following ination is required regarding the installation a maximum, normal and minimum flowrates i.e. will one flowmeter cover this flow range; NOTEWhere reference volumes are used, the pressure and temperature should be clearly stated; general statements such as “standard pressure and temperature S.T.P.” should not be relied upon. b accuracy required; c maximum permissible pressure loss. 4.2 Pipe The following ination is required regarding the pipe a material, temperature coefficient of expansion; b operating temperature; c internal diameter, how obtained the mean of six measurements or as specified in the relevant pipe standards, uniity; d layout, e.g. upstream, downstream fittings, straight lengths influence on b limits; e attitude, i.e. vertical, horizontal or sloping; f internal roughness of pipe. 4.3 Pressure differential device The following ination is required regarding the pressure differential device a type e.g. squared-edged orifice plate, nozzle, venturi; b suitability for the application; c limits on d, D, b and ReD; d mounting, i.e. slip plate, carrier; e tappings, i.e. location, number of, diameter; f material, temperature coefficient of expansion, operating temperature; g diameter; h drain hole diameter; i strength of orifice plate material to calculate deation under flow conditions. 4.4 Fluid The following ination is required regarding the fluid a state and composition; b operating temperature and pressure and local barometric pressure if appropriate; c density at operating conditions; NOTEFor gases density at reference conditions is also often required. d viscosity at operating conditions; e for compressible fluids only, isentropic exponent ratio of specific heats for ideal gases; f nature of flow, i.e. viscous or turbulent. 4.5 Differential pressure measuring device The following ination is required regarding the differential pressure measuring device a type microdisplacement, displacement, wet or dry i.e. manometric or mechanical, calibration correction factors; b span fixed or adjustable, maximum permitted pressure loss for the installation in question; c maximum operating pressure and temperature of the pressure difference measuring device; d corrosion resistance to metered fluid. Licensed Copy AUB User, na, Sat Jul 07 124900 GMT0000 2007, Uncontrolled Copy, c BSI w w w . b z f x w . c o m BS 1042-1.41992 BSI 12-19983 4.6 Basic equations The basic equations for the following are required a mass flow or volumetric flow; b compressible or incompressible fluids; c Reynolds number; d uncertainties. 5 Basic equations In the calculation sequences that follow, SI units are used. If it is the user’s practice to use other units, these should be converted into the appropriate SI units. The following equations for mass flowrate, qm, and volume flowrate, qv, are given in 5.1 of BS 1042-1.11992. where If the flowmeter is to be calibrated in units of volume flowrate referred to standard or other specified conditions of pressure and temperature, qo, then the following equation should be used, the suffix “0” denoting standard conditions of pressure and temperature. The above equations enable calculations described in items a to c of clause 3 to be made. Since a, C, E, d and p are unknown, the equations can be transposed to The values of d and D in the above equations are to be corrected for the effect of fluid temperature. At temperatures within 10 C of the temperature at which D and d are determined, the measured diameter values are sufficiently accurate, but at temperatures outside this range, corrections for expansion or contraction are necessary. It is also convenient to transpose the equations for Reynolds number ReD and Red given in 3.3.2 of BS 1042-1.11992 into the following. and NOTEIn the equations for mass flowrate the dynamic viscosity, m, is used and for volume flowrate the kinematic viscosity, y, is used. However, as the dynamic viscosity is equal to the kinematic viscosity multiplied by the density, the appropriate viscosity can be obtained. 6 Calculation of orifice or throat diameter 6.1 General The procedure for assessment of the differential pressure and calculation of the orifice or throat diameter to measure a stated flowrate of a given fluid in a given pipeline at specified conditions of pressure and temperature is described. The relevant clause references are given at the beginning of each step. 6.2 Procedure NOTESee clauses 6 and 7 of BS 1042-1.11992, sections 2 and 3 of BS 1042-1.21989 and 4.2 and 4.3 of this standard. Before proceeding with the details of the calculation, check the suitability of the device for the application in question and the general acceptability of the pipeline configuration. NOTEThe example for each item is given in the corresponding item of 6.3. a Calculate the pipe internal diameter, D, at the operating temperature, t C, preferably using the measured diameter or if this is not possible the diameter obtained from the relevant pipe standards. See 12.2. b Obtain/calculate the fluid density at reference conditions required only for gas flows measured in volume units at reference conditions of pressure and temperature. Obtain the compressibility factor of the gas at operating conditions. qmαε π 4 -- - d22∆pρ1 12 ⁄ CEε π 4 --- d22∆pρ1 12 ⁄ qvαε π 4 -- - d22∆p ρ1⁄ 12 ⁄ CEε π 4 -- -d 2 2∆ p ρ1⁄ 1 2 ⁄ E11β4– 12 ⁄ ⁄ βd D⁄ qoqv ρ 1 ρ 0 ------ - CEβ2 4qm επD22∆pρ1 12 ⁄ ---------------------------------------------- - 4qv επD22∆ p ρ1⁄ 12 ⁄ ---------------------------------------------------- - ReD 4qm πD1 --------------- - 4qv πDυ1 --------------- - Red 4qm πd1 -------------- - 4qv πd1 -------------- - Licensed Copy AUB User, na, Sat Jul 07 124900 GMT0000 20