FISHERMETER. Vortex flowmeter VT4000. liquid gas steam

Transcription

1 Vortex flowmeter VT00 liquid gas steam

2 Vortex Flowmeter VT00 No moving parts and reliable stainless steel structure Optimum measuring process reliability enabled by Digital Signal Processing (DSP) Measuring accuracy: ±1.0% Measurable medium: liquid, gas and steam VT00 is fitted with HART communication High working pressure, 42MPa (.) Output: 4-20mA analog signal & configurable pulse output Optional double sensors design with higher stability and reliability 1

3 Technical parameter Item VT00 Fig.1 Typical Diameter Nominal pressure Fluid temperature Sensor design Body material Accuracy Repeatability Flow Range Converter type Communication Wafer DN15~DN, Flange DN15~DN600, Insertion >= DN (1.6, 2.0, 2.5, 4.0, 5.0, 6.4) MPa. Other special pressure classes upon request Standard(-~+120), M-tem(-~+250), H-tem(-~+320) Single sensor or double sensors SS304, 316L, HC and other materials upon request ±1.0% < 0.33% 1:10~1:20 Compact & Remote HART Protocol Display T/P compensation Supply power LCD In preparation 15~28 V DC Output Current:4-20mA PulseVoltage : L<1V, H 5V Battery power Linear rectification Low flow cut-off Ex-Design Protection Class Applicable medium Ambient conditions Optional Available Available Ex ia II CT5,Ex d II CT5 IP Gas, liquid, steam Ambient temperature: (-~+60) Relative humidity: 5%~90% Atmospheric pressure: (86~106)kPa 2

4 Measuring principle The vortex flowmeter is used for measuring the flow velocity vof gases and liquids in pipelines flowing full. The measuring Principle is based on the development of a Karman vortex shedding street in the wake of a body built in the pipeline. The periodic shedding of eddies occurs first from one side and then from the other side of a bluff body (vortex-shedding -body) installed perpendicular to the pipe axis. Vortex shedding generates a so-called Karman vortex street with alternating pressure conditions whose frequency is proportional to the flow velocity. (Fig.2) Fig.2 The vortex shedding frequency f is proportional to flow velocity v and inversely proportional to the width of the shedder d: f = St v / d St, the Strouhal Number, is a dimensionless quantity. If the geometrical shape and dimension of shedder are designed appropriately, St is a constant over the wide range of Reynolds number Re (Figure 3). Re = v D / υ υ: Kenematic viscosity of fluid D: Meter body diameter Strouhal number St Fig.3 The vortex shedding frequency used to measure the flowrate is only a function of the flow velocity regardless of fluid density and viscosity. The pressure pulsation generating with vortex shedding will be detected by the Piezo-Sensor and converted into pulse signal corresponding to the vortex frequency in the test circuit, and the signal converter will convert this pulse signal into 4-20 ma normalized current signal and output it. 3

5 Flowmeter Size Selection The flowmeter size is determined from the imum operating flowrate Q V. To achieve the imum flow range, this value should not be less than one half of the imum flowrate for the meter size (RangeMax), but can be selected as low as 0.15 RangeMax. The start of the linear flow range is a function of the Reynolds Number. If the flowrate to be measured is specified as normal flowrate, (normal conditions: 0 C, 1013 mbar) or as mass flowrate, the values must first be converted to actual flowrate values at operating conditions and then the appropriate meter size can be selected from the Flow Range Tables (Tbls. 1, 2, 3). 1. Convert normal density ( ρn ) --> operating density ( ρ ) 1,013 + p 273 ρ = ρ n , T ρ = Operating density [kg/m 3 ] ρ N = Normal density [kg/m 3 ] p = Operating pressure [bar] T = Operating temperature [ C] Q V = Operating flowrate [m 3 /h] Q n = Normal flowrate [m 3 /h] Q m = Mass flowrate [kg/h] η = Dynamic viscosity [Pas] ν = Kinematic viscosity [m 2 /s] 2. Convert to flowrate at operating conditions (Q V ) a) starting with normal flowrate (Q n ) --> ρn Q V Q n ρ Q 1, T = = n ,013 + p 273 b) starting with Mass flowrate (Q m ) --> Q Q m V = ρ 3. Dynamic viscosity ( η ) --> kinematic viscosity ( ν ) η ν = -- ρ 0 DN DN250 DN DN150 DN DN80 Q V min [m 3 /h] 10 DN25 DN50 DN DN ν [10-6 m 2 /s = cst] Fig. 4: Minimum Flowrate, Liquids as a Function of the Kinematic Viscosity 4

6 Flow Ranges, Liquids Meter DIN ANSI Size Q V min 1) RangeMax Frequency Q V min 1) RangeMax Frequency [m 3 /h] [m 3 /h] [Hz] [m 3 /h] [m 3 /h] [Hz] DN Inch Std. HT at Q v Std. HT at Q v 15 1/ / Tbl. 1: Flow Ranges, Liquids at 20 C, 1013 mbar, ρ = 998 kg/m 3 ) 1) Std. 280 C Version / HT = High temperature design (f = 0 C Pressure Drop, Liquids See Fig. 5 for water (20 C, 1013 mbar, ρ = 998 kg/m 3 ). For other densities ( ρ ) the pressure drop can be calculated using the following equation: ρ p' = p 998 Static Overpressure, Liquids To avoid cavitation when metering liquids a positive static pressure (back pressure) is required downstream from the flowmeter. The required pressure can be calculated using the following equation: p x p vapor x p' p 2 = p vapor = p' positive downsteam static pressure [mbar] vapor pressure of fluid at the operating temperature [mbar] = pressure drop, fluid [mbar] Example for liquids: Find the flowmeter size for metering 55 m 3 /h liquid with a density of 850 kg/m 3 and a kinematic viscosity of 2 cst = (2 x 10-6 m 2 /s). 1. Q V =. 55 m 3 /h --> DN50[2 ] (per Tbl. 1): Q V = 70 m 3 /h 2. Flow range start, linear, at 2 cst, (from Fig. 5): Q V min = 6 m 3 /h 3. Press. drop (Q v = 55 m 3 /h) at ρ= 850 kg/m 3 : p' = 425 mbar p' = Pressure drop fluid [mbar] p = Pressure drop water [mbar] (from Fig. 5) 0 Example 425 mbar p [mbar] DN 15 DN 25 DN DN 50 DN 80 DN DN DN 250 DN 150 DN Q V [m 3 /h] 55 m 3 /h Fig. 5: Pressure Drop, Water (20 C, 1013 mbar, ρ = 998 kg/m 3 ), DIN-Design 5

7 Flow Ranges, Gas/Steam Meter DIN ANSI Size Q V min 1) RangeMax Frequency Q V min 1) RangeMax Frequency [m 3 /h] [m 3 /h] [Hz] [m 3 /h] [m 3 /h] [Hz] DN Inch Std. HT at Q v Std. HT at Q v 15 1/ / Tbl. 2: Flow Ranges, Gases at ρ = 1.2 kg/m 3 ) 1) Std. 280 C Version / HT = High temperature design (f = 0 C Example for Gases: Find the flowmeter size for metering 25 m 3 /h (q n ) CO 2 -Gas; Temp. = 85 C, Press. = 5 bar a. For details see Page 5 Flowmeter Size Selection ρ = 1.97 kg/m 3 n (CO 2 ) 1. Convert ρ --> : =7.4 kg/m 3 n ρ ρ 2. Convert m 3 /h (q n ) --> m 3 /h (q v ): Q V = 676 m 3 /h (q v ) --> Selection : DN 80[3 ] (Q V = 1 m 3 /h) (q v ) 3. Pressure drop at ρ= 7.4 kg/m 3 : p' = mbar 4. Flow range start at ρ = 7.4 kg/m 3 (from Fig. 7): Q V min = 45m 3 /h, Convert m 3 /h (q v ) --> m 3 /h (q n ): Q V min = 169 m 3 /h (q n ) Pressure Drop, Gas/Steam See Fig. 8 for air (at 20 C, 1013 mbar, ρ = 1.2 kg/m 3 ) For other fluid densities the pressure drop can be calculated using the following equation: ρ p' = p 1,2 p' = Pressure drop fluid [mbar] p = Pressure drop air [mbar] (from Fig. 8) Normal Densities of Various Gases: Gas Normal Density [kg/m 3 ] Acetylene Air Ammonia Argon Butane Carbon dioxide Carbon monoxide Ethan Ethylene Hydrogen Methane Natural gas Neon Nitrogen Oxygen Propane Propylene DN DN250 Q V min [m 3 /h].0 DN DN150 DN DN80 DN50 DN 10.0 DN25 DN ρ [kg/m 3 ] Fig. 6: Minimum Flowrates, Gas/Steam as a Function of the Fluid Density, DIN-Design (280 C) 6

8 DN DN250 DN DN150 Q V min [m 3 /h].0 DN DN80 DN50 DN DN ρ [kg/m 3 ] Fig. 7: Minimum Flowrates, Gas/Steam as a Function of the Fluid Density, DIN-Design (HT) p [mbar] DN15 DN25 DN50 DN DN80 DN DN150 DN DN250 DN Q V [m 3 /h] Fig. 8: Pressure Drop, Air (20 C, 1013 mbar, = 1.2 kg/m 3 ), DIN-Design 7

9 Flowrates Saturated Steam [kg/h] Example for Saturated Steam: Find the flow range for DN 50 [2 ] at 7 bar (a). --> from Tbl. 3: DN 50[2 ]: kg/h Additional information: Sat. steam temp.= 1 C Sat. steam dens.= 3.67 kg/m 3 p[bar a] Meter Size Inch DN 1/2 15 min min /2 min min min min min min min min Density ρ sat [kg/m 3 ] Temp. Tsat [ C] Tbl. 3: Saturated Steam Flow Ranges, DIN-Design 8

10 Ordering Selection of Vortex Flowmeter Order series VT Converter type 4 Type of connection Wafer (DN15~DN) 0 Flange (DN15~DN600) 1 Insertion ( DN350) 2 Type of converter Compact 0 Remote 1 Measuring medium Liquid 0 Gas 1 Steam 2 Materials SS L HC Others Meter Size DN15 15 DN20 20 DN25 25 DN DN50 50 DN80 80 DN 1H DN125 1T DN150 1F DN 2H DN250 2F DN... DN800 3H... 8H Pressure Rating PN16 PN20 PN25 PN PN63 PN 150LB LB 600LB Others Probe type Standard (-~+120) 0 High temperature (-~+250) 1 Super temperature (-~+320) 2 Sealing Graphite 0 PTFE 1 Others 9 Explosion proof None Exia ia II II CT5 CT5 Ex d II CT5 HART None 0 Yes 1 A B C M B L C D E F G K N P A B C 9

11 Profile and installing dimension Flange connection (mm) DN PN 16/ 16/ 16/ 16/25 16/25 16/25 L H d D / / / 3/360 5/ /485 k / /220 2/ / / /430 d /22 18/26 22/26 22/26 26/30 26/30 N /16 b /24 22/26 24/28 24/30 26/32 28/34 DN PN L 120 H D d Wafer connection (mm) FISHERMETER

12 Installation The installation site and fixing manner of flowmeter will have a direct impact on its application. Incorrect installation will influence the measuring accuracy and the service life of the flowmeter, and even cause permanent damage to it, so the following items shall be referred during the installation. Inlet and outlet sections The installation of flowmeter shall satisfy the minimum requirements for the inlet and outlet straight section as shown Figure 9, or it will have a serious impact on the measuring accuracy or even on normal function of flowmeter. Figure 9 Length of inlet and outlet straight section (D: The nominal internal diameter of the meter) Installation for high fluid temperatures When the temperature of medium in the horizontal pipe is above 180, it is recommended that the remote type of flowmeter or side mounting be chosen, that is to say, the head of flowmeter is not on the top of the pipe, because high temperature may damage the electronic circuit in signal converter. Correct installation manner is as shown in Fig.10 Fig.10: Installation for high fluid temperatures (Temperature 180 ). Fig.11: Low installation shall be avoided for steam measurement Installation for steam measurement When the measured medium is saturated steam or humid gas, the flowmeter shall not be installed at the lowest part of pipe line (Fig.11), because the steam may condense into liquid at the lower part of pipe line, causing coexisting of water and steam, which may result in failure in performance of flowmeter and greater measuring errors. In addition, when the steam device is being opened, water hammer may appear at the lower part of pipe line. 11

13 Installation for liquid measurement When the measured medium is liquid, the liquid shall be full of the pipe, and it is better to make the liquid flow from a lower position to a higher or flow horizontally. The flowmeter shall not be installed at the highest part of pipe line (Fig.12), because the air bubbles may gather there and cause a serious impact on the measuring accuracy. If the pipe is vertical, the liquid shall not flow from up to down (Fig.13), or the pipe will not be full, which may seriously influence the measuring accuracy and cause failure in performance of flowmeter. Fig.12: High installation shall be avoided for liquid measurement Fig.13: Up-to-down flow shall be avoided for installation of vertical pipe line Thickness of thermal insulation layer If the pipe line needs to be kept warm, the thickness of thermal insulation layer covering the instrument shall not exceed 50 mm (Figure 14). The excessive thickness may cause a rise in temperature of signal converter which leads to a damage. Fig.14: Thickness of thermal insulation layer Fig.15:Required distance forflowmeter maintenance Service clearance More than mm clear space for mounting, dismounting and maintenance shall be allowed at the top of flowmeter during installation (Figure 15). Installation of Remote type flowmter The installation of separate flowmeter body is identical to that of compact flowmeter. The signal converter must be firmly fixed on the wall or in the cabinet. The longest transmission distance between the signal converter and primary body is 10 meters, and the connecting cable is two-core shielded cable. The shorter the signal transmission distance is, the less the interference. So it is needed to shorten the cable length according to actual need and cut the excessive cable. The unamplified signals from the transducer to signal converter may be easily interfered during transmission, so care must be taken to connect wires and the shielding layer shall be grounded reliably at the same place where the power is grounded. After grounding, the cable shall be fixed and better in the special cable trunk (Figure 16). 12

14 Precaution Try to avoid vibration, and rubber the support or connect by the hose if necessary. If the pressure fluctuation occurs when there is no flow in a long pipe, a gate valve is needed to be installed before and after the flowmeter. If water is contained in the steam or steam in water, a water separator shall be equipped. Installations for wafer type, flange connection and insertion type are separately as shown in Figure 17, 18 and 19. Fig.16: Remote type Fig.17: Wafer type Fig.18: Flange connection Fig.19: Insertion type 13

15 Contact us Once a quotation inquiry is received, a regional sales representative will contact you within 24 to 48 hours. International Sales Department Tel: Fax: sales@fishermeter.com Technical Service Tel; / / 606 Fax: service@fishermeter.com Office Address Beijing Fishermeter Instrument Co., Ltd. Post Code: 107 Room 1204, B Block Fortune Center, Tianlang Garden, Beiyuan Road, Chaoyang District, Beijing, China. (107) Factory Address 1 st building, Mauhwa Industry Park 1st block, Caida 3rd street, Caiyuan Industry Park, Nancaizhen Town, Shunyi District, Beijing, China. 14