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1、J I S Z*87bb 89 4933608 0079953 3 7- JAPANESE INDUSTRIAL STANDARD Methods of Flow Measurement by Vortex Flowmeters JIS Z 8 7 6 6 - 1 9 8 9 Translated and Published by Japanese Standards Association UDC 532.575.9 Printed in Japan 11 s Copyright Japanese Standards Association Provided by IHS under lic
2、ense with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/16/2007 00:35:43 MDTNo reproduction or networking permitted without license from IHS -,-,- J I S Zx87bb 89 W 4933608 0079954 5 111 in the event of any doubt arising, the original Standard in Japanese is to be final
3、authority. Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/16/2007 00:35:43 MDTNo reproduction or networking permitted without license from IHS -,-,- J I S Z*87bb 89 m 4933b08 0079955 7 m UDC 532.5
4、75.9 JAPANESE INDUSTRIAL STANDARD J I S Methods of Flow Measurement by 2 8766-1989 Vortex Flowmeters 1. Scope This Japanese Industrial Standard specifies methods of flow measurement for fluids in pipes running full by means of vortex flowmeters, hereinafter referred to as the llflowmetersll. 2. Defi
5、nitions The definitions used in this Standard are defined as follows, besides defined in JIS Z 8103. vortex generator in the measuring tube in order to generate vortices. A cylindrical or other non-streamline shape body vortex frequency one side of the vortex generator within a unit time. The number
6、 of Krman vortices discharged from measuring tube in which the vortex generator is mounted. The conduit part through which the fluid flows, and vortex detecting element and discharge. converter obtained by the vortex detecting element and converts it to an output signal. A device which detects vorte
7、x generation A device which amplifies and shapes the vortex signal integrator indicate the integrated value of flow rate. A device which receives the converter output signal to compressibility factor (2) A correction factor used to express the state equation of real gas as P-U=Z.R.T. where p : absol
8、ute pressure v : specific volume R : gas constant T : absolute temperature Applicable Standards : JIS C 0903-Electrical Apparatus for Explosive Atmospheres in General Industry JIS C 0920-Test Methods on Electrical Apparatus for Use in Gassy Coal Mines JIS Z 8103-Glossary of Terms Used in Instrumenta
9、tion Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/16/2007 00:35:43 MDTNo reproduction or networking permitted without license from IHS -,-,- J I S Z*87bb 89 4933608 007995b 9 m 2 2 8766-1989 (8)
10、 K factor (K) flowmeter at the tested flow rate to the number of output pulses from the flowmeter (number of pulses/unit volume). The ratio of unit volume of fluid flows through the (9) meter factor (i,) The ratio of the volume of fluid flow through the flowmeter to the corresponding number of outpu
11、t pulses from the flowmeter at the tested flow rate (volume/number of pulses). Remark: Although K factor (KI is used for explanation in this Standard, it is alos possible to apply the meter factor (MJ as M,=l/K. (10.) flow rate (volume flow rate, mass flow rate, weight flow rate) The volume, mass or
12、 weight of fluid flowing through the flowmeter in a unit time. (11) flow rate range flow rates. The range between the minimum and the maximum (12) maximum flow rate The maximum flow rate recommended for the flowmeter by its manufacturer. (13) minimum flow rate The minimum flow rate recommended for t
13、he flowmeter by its manufacturer. (14) straight pipe section downstream sides of the flowmeter to reduce the measurement error. The necessary minimum length of this straight pipe section is called “required minimum straight length of pipe“, rectifier eliminate or reduce swirls, drifts and contractio
14、ns in the flow in order to reduce their influence on the flowmeters characteristics. Straight pipe connected to the upstream and (15) A device used on the upstream side of a flowmeter to (16) strainer A device such as a metal mesh installed on the upstream side of a flowmeter to remove foreign matte
15、rs from the flow. (17) temperature correction or computed value to correct the measurement to a value at a reference temperature or temperature of use. Also, that value itself. The adding of a certain value to a read out Remark: There are following two types of correction. (1) Variation of volume of
16、 the measured fluid due to temperature variation. (2) Variation of K factor due to temperature variation. (18) pressure correction The adding of a certain value to a read out or computed value to correct the measurement value to a value at a reference pressure or pressure of use. Also, that value it
17、self. Remark: The correction is for variation of volume of the measured fluid due to pressure variations. Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/16/2007 00:35:43 MDTNo reproduction or netw
18、orking permitted without license from IHS -,-,- JIS Z*87bb 89 E 4733608 0079957 O E 3 2 8766-1989 (19) Reynolds number (Red to formula (1) based on the pipe inside diameter and fluid state at A numerical value to be determined according the pressure measuring point. - - (1) . ReD=- U - D V where Reo
19、: Reynolds number based on D - u : average velocity of fluid in pipe section D : pipe inside diameter v : kinematic viscosity of fluid (20) pressure loss The pressure loss due to installation of the flowmeter. 3. Principle of Method of Measurement As shown in Fig. 1, a regular train of vortices, kno
20、wn as a Krman vortex street, is formed at downstream of a vortex generator positioned vertically to the stream. For a given width of the vortex generator d, a flow velocity U, and a vortex frequency f, a dimensionless nubmer S, related to vortex shedding frequency is defined by formula (2). . ( 2 )
21、s - f * d ,- u This dimensionless number called the Strouhal number, and is a function of Reynolds number, but is nearly Constant over a certain range of Reynolds number, allowing to find the flow velocity U from the vortex frequency f. Vortex flowmeters are constructed based on this principle. Fig.
22、 1. Krman Vortex Street Krman vortex + generator Flow Fig. 2. Principle of Method of Measurement Vortex generator Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/16/2007 00:35:43 MDTNo reproduction
23、 or networking permitted without license from IHS -,-,- J I S Z*8bb 89 W 4933608 0079958 2 m 4 Z 8766-1989 Fig. 2 is a diagram of the principle of flowmeter. As Fig. 2 shows, when a fluid flows through the measuring tube in which a vortex generator is mounted, vortices are generated with a frequency
24、 nearly proportional to the velocity of the fluid. an electrical signal, an output signal corresponding to the flow rate is obtained. By detecting the number of generated vortices as 4. Reauired Matters for Measurement The basic matters required for measurement shall be as follows: (1) That the laye
25、r phase, and also the approximate density and viscosity (2) (or kinematic viscosity) of the fluid are known. That the fluid to be measured is a single phase while passing through the flowmeter, and the measuring body runs full. (3) (4) That the fluid to be measured flow can be regarded as nearly ste
26、ady flow. That mixed-in matters (foreign matters) are removed so as not to hinder the measurement. (5) That there is little contamination of the output signal by noise. (6) That straight pipe sections of the required lengths are installed at upstream and downstream sides of the flowmeter. 5. Flowmet
27、er Configuration The flowmeter should be composed principally of a measuring tube, vortex generator, vortex detecting part, and converter (see Fig. 3). Fig. 3. Example of Flowmeter Configuration /Onverter Flow - Remark: This diagram is only for illustration of nomenclature of each part, and is not i
28、ntended to stipulate configuration. Note that there are also units having an integrator built in the converter. Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/16/2007 00:35:43 MDTNo reproduction o
29、r networking permitted without license from IHS -,-,- J I S Z*87bb 89 4933608 0079959 4 m 5 Z 8766-1989 6. Flowmeter Selection *a The flowmeter shall be selected according to the using conditions, taking into consideration the following matters in particular Flow Range flow rates in relation to the
30、allowable measurement uncertainty. Care shall be given to the maximum and the minimum Bore Diameter The bore diameter shall be the same as the bore diameter of the upstream and downstream straight pipe sections. Construction be considered according to the installation location. Water-tightness ( l)
31、and explosion prevention (2) shall Notes (l) Refer to JIS C 0920 (2) Refer to JIS C 0903 Properties of Measuring Fluid Attention shall be paid to density, viscosity, vapor pressure , corrosiveness , existence of entrained matters (foreign matters) and, depending on the type of vortex detecting part,
32、 whether a gas contains mist or water droplets. Temperature Attention shall be paid to fluid temperature, and ambient temperature at the location where the flowmeter is used. Pressure , Pressure Loss and Downstream Side Pressure Attention shall be paid to the pressure of the fluid, pressure loss in
33、the flowmeter, and, in the case of liquid instrumentation, to the down- stream side pressure required to prevent cavitation. Materials the fluid to be measured shall be selected for the materials used for the measuring tube , vortex generator , vortex detecting part , etc. Characteristics of the Flo
34、w Rate rate (or Reynolds number) to instrumental error (or K factor) re- lationship, and the flow rate to pressure loss relationship. Taking (4) to (6) into consideration , materials suitable for Attention shall be paid to the flow Connection Construction A construction shall be selected appropriate
35、 for the piping, taking into consideration the fluid temperature and pressure ranges Type of Output Signal Pulse train corresponding to vortex frequency, analog current or voltage corresponding to flow rate output impedance and time constant of response of analog signal shall be considered. Power So
36、urce Division of a.c. or d.c., voltage, frequency, and power consumption shall be considered. Piping Attention shall be paid to upstream and downstream straight. piping lengths for flowmeter, and to layout and makeup of connecting piping. Copyright Japanese Standards Association Provided by IHS unde
37、r license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/16/2007 00:35:43 MDTNo reproduction or networking permitted without license from IHS -,-,- J I S Z*87bb 89 I 4933b08 00799b0 O = 6 Z 8766-1989 7. Flowmeter Installation 7.1 Installation Location The following g
38、eneral precautions shall be observed in determining the installation location for the flowmeter selected in accordance with 6. (1) Avoid mounting near electrical appliance which may interfere with measurement. (2) Avoid as much as possible locations where high or low temperatures or radiant heat is
39、frequent. (3) Avoid as much as possible locations with highly corrosive atmospheres, and locations with high humidity. (4) Avoid as much as possible locations with hard vibration. (5) Locations with space allowing daily inspection , and permitting easy wiring and piping works are desirable. 7.2 Pipi
40、ng The following matters shall be considered when performing piping work for the installation of flowmeters and accessory devices. (1) Flowmeter flow direction shall be verified. (2) Straight pipe sections of the required lengths shall be installed at the flowmeter upstream and downstream sides, and
41、 those straight pipe lengths shall fulfill each of the following requirements (refer to Fig. 4). (a) They shall be of circular.tubes. (b) They shall be straight, with minimum step difference. (c) There shall be no valves or bypass piping immediately ahead of or immediately after them, and their inte
42、rnal surfaces shall be clean and free of pits and accretions. Remark: The straight pipe section lengths differ depending on flowmeter construction. (3) If a strainer is used, it shall be mounted at upstream of the rectifier or straight pipe section. (4) Temperature measurements on the fluid shall be
43、 carried out at down- stream of the flowmeter in such a way as not to disturb the flow and at upstream side of control valve. (5) Pressure measurements on the fluid shall be carried out at a position of 2 to 7 D (pipe line bore) from the downstream end plane of the flowmeter. (6) Care shall be taken
44、 that the straight pipe sections adjacent to the flowmeter are coaxial with the flowmeter. Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/16/2007 00:35:43 MDTNo reproduction or networking permitte
45、d without license from IHS -,-,- , J I S Z*87bb 89 E 4933608 00799bL 2 7 Z 8766-1989 Fig. 4. Straight Pipe Lengths for Flowmeter Upstream side Downstream side straight - - The inside diameters of the straight pipe parts adjacent to the flowmeter shall be practically the same as the inside diameter o
46、f the flowmeter. Gaskets between the flowmeter and the adjacent straight pipe part shall not intrude into the flow path. It is desirable that the flowmeter is installed with the posture recommended by the flowmeter manufacturer. The flowmeter shall be protected from vibration and excessive piping st
47、ress. The flowmeter shall be protected from excessive pressures resulting from pressure fluctuations and from the thermal expansion of liquid. In the case of liquid measurement, consideration shall be given to ensuring that the liquid is running full in piping. install so that the liquid flows from
48、bottom to top. For example, It is desirable in practice to install. a bypass as shown in Fig. 5 for purposes of inspection and cleaning of the flowmeter. Fig. 5. Bypass Piping Bypass piping valve /- :ztG-EErpl=ynD Downstream side valve upstream side valve Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/16/2007 00:35:43 MDTNo reproduction or networking permitted without license from IHS -,-,