SELECCIÓN DE CAUDALIMETROS. Tablas de Fabricantes

Transcription

1 SELECCIÓN DE CAUDALIMETROS Tablas de Fabricantes

2 Flow Meter Selection Table Página 1 de 1 17/09/2007 KEY Best for this application OK with some exceptions OK for some applications but check first Do not use in this service Magnetic Thermal Mass Ultrasonic - Transit Time Ultrasonic - Doppler Vortex Shedding Turbine Variable Area Postive Displacement Differential Pressure

3 Flowmeter Selection Guide Fluid Type Technology Clean Dirty Viscous Pressure Max Temp Max Press Pipe Diam's Typical Typical Sizes Liquid Liquid Liquid Slurry Gas Steam Loss F psi Req'd Turndown Accuracy inches Notes Magnetic None to 1.5% Rate.1 to 96 Fluid must be conductive Coriolis Medium None 40 to 1.25% Rate.1 to 8 Very accurate, MV, Mass Ultrasonic None or 5 to to 1.75% Rate 1 + Fastest growing pipe rat'g technology Vortex Low to to 1 1% Rate 2 to 12 Great steam flowmeter Turbine Low to to 1.5% Rate.25 to 24 Largest # of meters sold Diff. Pressure Medium to 30 5 to 1 2% FS Any Orifice, Venturi, Pitot, Flow elmt's Pos Displacement High None 15 to 1.5% Rate.25 to 16 Oval, Piston, Rotary Vane Variable Area Low None 10 to 1 2% FS 1/8 to 4 No power req'd, Metal Tube Open Channel Low 200 N/A None to to 1 2% FS 2 + Plant effluent, Flumes/Weirs Thermal Low None to to 1 1% FS 1/8 + Small MFC's to large ducts Intended Service Possibly Applicable Not Applicable This guide represents an overview of flowmeter selection and a thorough evaluation of each application should be done to ensure proper selection. Applied Engineering Inc 203 Wylderose Court Midlothian, VA

4 Material Phase Flowmeter Selection Table Flowmeter Clean Viscous Pressure Liquid Liquid Slurry Gas Solid Turndown Loss Upstream Straight Pipe Dia (Guide) Downstream Straight Pipe Dia (Guide) Typical Accruacy (% FSC) Coriolis Y Y Y 20:1 H None None 0.5 M Relative Cost Notes U' Tube are better than 'S' tube models but are however more expensive. Dall Tube Y Y N 3:1 M-H H Similar to venturi but cheaper to manufacture. Magnetic Y Y Y N N 10:1 N H Must be conductive Orifice Plate Y Y N 3:1 H to 2 L Limitation of accuracy is due to differential pressure sensing element. Pitot Tube Y N Y N 3:1 M to 5 L Pitot tube only provides point measurement of fluid flow in pipe. Positive Displacement Y Y N Y N 10:1 H None None 1 On dirty duty filter required. Turndown may be higher on Gas service. Solids Flowmeter N N N N Y 20:1 NA NA NA 2 H Target Meter Y Y Y N 4:1 H to 5 L Thermal Mass Flow Y Y N 20:1 M-H M On dirty duty filter required. Turbine Y N N 10:1 H Maitnenance costs high due to need to overhaul. Ultrasonic Y Y 10:1 N to 3 M Variable Area Y Y N 5:1 M None None 5 to 10 L Venturi Y Y N 3:1 M to 1 H Vortex Y N N Y N 10:1 H M Wier / Flumes Y N N 100:1 M See Link See Link 2-5% H Cost depends on size Clamp on meters difficult to get good / clean pipe connection. Generally these instruments provide local indication only. Limitation of accuracy is due to differential pressure sensing element. Y- Yes H- High N- No M- Medium - Sometimes L- Low N- None

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6 1 A Flow Measurement Orientation of Reynolds numbers (Re or R D ) within which the various flowmeter designs can operate. In selecting the right flowmeter, one of the first steps is to determine both the minimum and the maximum Reynolds numbers for the application. Maximum R D is obtained by making the calculation when flow and density are at their maximum and viscosity at its minimum. Conversely, the minimum R D is obtained by using minimum flow and density and maximum viscosity. If acceptable metering performance can be obtained from two different flowmeter categories and one has no moving parts, select the one without moving parts. Moving parts are a potential source of problems, not only for the obvious reasons of wear, lubrication, and sensitivity to coating, but also because moving parts require clearance spaces that sometimes introduce slippage into Table 1: Flowmeter Evaluation Table Orifice Square-Edged >1.5 (40) Honed Meter Run (12-40) Integrated <0.5 (12) Segmental Wedge <12 (300) Eccentric >2 (50) Segmental >4 (100) V-Cone ( ) Target*** <0.5(12) Venturi >2 (50) Flow Nozzle >2 (50) Low Loss Venturi >3 (75) Pitot >3 (75) Averaging Pitot >1 (25) Elbow >2 (50) Laminar (6-400) LINEAR SCALE TYPICAL RANGE 10:1 (Or better) Magnetic* -72 ( ) Positive Displacement Gas Liquid Turbine Gas Liquid Ultrasonic Time of Flight Doppler Variable-Area (Rotameter) Vortex Shedding Vortex Precession (Swirl) Fluidic Oscillation (Coanda) Mass Coriolis Thermal Probe Solids Flowmeter Correlation Capacitance Ultrasonic cp = centi Poise cs = centi Stokes = Some designs <12 (300) <12 (300) (6-600) (6-600) >0.5 (12) >0.5 (12) 3 (75) (40-400) <16 (400) >1.5 (40) (6-150) <72 (1800) <24 (600) <8 (200) >0.5 (12) GASES (VAPORS) FLOWMETER PIPE SIZE, in. (mm) SQUARE ROOT SCALE: MAIMUM SINGLE RANGE 4:1 (Typical)** = Normally applicable (worth consideration) = Designed for this application (generally suitable) PRESS VISCOUS STEAM CLEAN DIRTY HIGH LOW CLEAN HIGH LOW DIRTY LIQUIDS CORROSIVE VERY CORROSIVE SLURRIES FIBROUS ABRASIVE REVERSE FLOW PULSATING FLOW HIGH TEMPERATURE CRYOGENIC URV = Upper Range Value = Not applicable SEMI-FILLED PIPES NON-NEWTONIANS OPEN CHANNEL R D > 500 R D : 8,000-5,000,000 R D > 100 R D > 75,000Ł R D > 50,000Ł R D > 12,800Ł R D > 100,000Ł R D > 40,000Ł Ł R D < 500 R D > 4,500 - No R D limit 8,000 cs - Rp > 5,000, 15 cs R D > 4,000 No R D limit, < 100 cs, < 30 cp, < 5 cp R D > 2,000, < 80 cs No R D limit No R D limit - No data available No data available According to other sources, the minimum Reynolds number should be much higher Process temperature to 1000 F (540 C): Transmitter limited to F ( C) 700 (370) Process temperature to 1000 F (540 C): Transmitter limited to F ( C) * Liquid must be electrically conductive ** Range 10:1 for laminar, and 15:1 for target *** Newer designs linearize the signal TRANSACTIONS Volume 4 13 TYPICAL Accuracy, uncalibrated (Including transmitter) ±1-4% URV ±1% URV ±2-5% URV ±0.5% URV ±2-4% URV ±2-4% URV ±0.5-1% of rate ±0.5-5% URV ±0.5-2% URV ±1-2% URV ±1.25% URV ±3-5% URV ±1-2% URV ±5-10% URV ±1% of rate ±1% of rate ±1% of rate to ±5% URV ±1% of rate to ±5% URV ±1% of rate to ±10% URV ± % of rate ±2% of rate ±5-10% of rate ±1-2% URV to ±4% URV No data available ±6% of TYPICAL Reynolds number or viscosity TEMPERATURE F ( C) 150 (66) 360 (180) 250 (120) 600 (315) ( ) ( ) ( ) ( ) Glass: 400 (200) Metal: 1,000 (540) 400 (200) 536 (280) 350 (175) ( ) 1,500 (816) 750 (400) 300 (149) ( ) PRESSURE psig (kpa) To 4,000 psig (41,000 kpa) 600 (4,100) To 4,000 psig (41,000 kpa) 30 (225) 1,500 (10,800) 1,400 (10,000) 1,400 (10,000) 3,000 (21,000) 3,000 (21,000) Glass: 350 (2,400) Metal: 720 (5,000) 1,500 (10,500) 720 (5,000) 5,700 (39,900) 580 (4,000) 580 (4,000)

7 A Flow Measurement Orientation 1 the flow being measured. Even with well maintained and calibrated meters, this unmeasured flow varies with changes in fluid viscosity and temperature. Changes in temperature also change the internal dimensions of the meter and require compensation. Furthermore, if one can obtain the same performance from both a full flowmeter and a point sensor, it is generally advisable to use the flowmeter. Because point sensors do not look at the full flow, they read accurately only if they are inserted to a depth where the flow velocity is Table 2: Orientation Table For Flow Sensors TYPE OF DESIGN Orifice (plate or integral cell) Segmental Wedge V-Cone Flowmeter Target Meters Venturi Tubes Flow Nozzles Pitot Tubes Elbow Taps Laminar Flowmeters Magnetic Flowmeters Positive Displacement Gas Meters Positive Displacement Liquid Meters Turbine Flowmeters Ultrasonic Flowmeters Time of Flight Doppler Variable Area (Rotamater) Vortex Shedding Fluidic Oscillation (Coanda) Mass Flowmeters Coriolis Mass Flowmeters Thermal Probe Solids Flowmeters Weirs, Flumes = Non-standard Range L = Limited = Some Designs H = High A = Average M = Minimal N = None SR = Square Root DIRECT MASS-FLOW SENSOR DIFFERENTIAL PRESSURE-FLOW SENSOR VOLUME DISPLACEMENT-FLOW SENSOR VELOCITY-FLOW SENSOR EPECTED ERROR FROM VISCOSITY CHANGE TRANSMITTER AVAILABLE LINEAR OUTPUT RANGEABILITY PRESSURE LOSS THRU SENSOR APPRO. STRAIGHT PIPE-RUN REQUIREMENT ➀➄ (UPSTREAM DIAM./DOWNSTREAM DIAM.) H SR 3:1 H 20/5 M SR 3:1 A 20/5 SR 3:1 to 15:1 M 2/5 A SR 15:1 M 20/5 H SR 3:1 M 15/5 H SR 3:1 A 20/5 M SR 3:1 M 30/5 M SR 3:1 N 25/10 10:1 H 15/5 N 30:1 ➆ N 5/3 10:1 to M N 200:1 M ➆ 10:1 A N H 10:1 ➇ A 15/5 N N 20:1 10:1 N N 20/5 20/5 A 10:1 M N A 10/1 ➅ A 20/5 A 12/1➅ H 20/5 N 20:1 M/H N N 20:1➆ M 20/5 5:1 to 80:1-5/3 M 100:1 M 4/1 ➀ = The data in this column is for general guidance only. = Inherent rangeability of primary device is substantially greater than shown. Value used reflects limitations of differential pressure sensing device when 1% of rate accuracy is desired. With multiple-range intelligent transmitters, rangeability can reach 10:1. ➂ = Pipe size establishes the upper limit. ➃ = Practically unlimited with probe type design. 14 Volume 4 TRANSACTIONS cc/min FLOW RANGE ➈ cc/min Sm 3 /hr or Am 3 /hr kgm/hr Solids Flow Units Gas Flow Units Liquid m 3 /hr Flow Units gpm ➂ ACFM Sm 3 /hr ➃ ➂ ➃ ➂ ➂ ACFM Sm 3 /hr lbm kgm/hr lbm kgm/hr ➂ ➄ = Varies with upstream disturbance. ➅ = Can be more with high Reynolds number services. ➆ = Up to 100:1. ➇ = More for gas turbine meters. ➈ = Higher and lower flow ranges may be available. Check several manufacturers.

8 General Guidelines for Flow Meter Selection Flow Meter Turbine Positive Displacement Electromagnetic (Mag-Meter) Variable Area (VA, Rotameter) Thermal Mass Flow (TMF) Coriolis Mass Meter Orifice Plate Recommended Service Clean, viscous liquids Clean, viscous liquids Clean, dirty, viscous, conductive liquids and slurries Clean, dirty, viscous liquids Clean dirty viscous liquids some slurries Clean, dirty. viscous liquids, some slurries Clean, dirty, liquids some slurries Turndown 20 to 1 High 10 to 1 High 40 to 1 None 10 to 1 Medium Typical Typical Required Effects Pressure Accuracy Upstream from Loss pipe, changing diameters viscosity FS = Full Scale +/- 0.25% of rate +/- 0.5% of rate +/- 0.5% of rate +/- 1 to 10% FS 5 to 10 High None High 5 None None Medium 10 to 1 Low +/- 1% FS None None 10 to 1 Low 4 to 1 Some Pitot tube Clean liquids 3 to 1 Very low Ultrasonic (Doppler) Ultrasonic (Transit Time) Venturi Vortex Dirty, viscous, liquids and slurries Clean, viscous, liquids some dirty liquids (depending on brand) Some slurries but clean, dirty and liquids with high viscosity Clean, dirty liquids +/- 0.5% of rate +/- 2 to 4% FS +/- 3 to 5% FS None None 10 to 20 High 20 to 30 Low 10 to 1 None +/- 5% FS 5 to 30 None 40 to 1 None +/- 1 to 3% FS 10 None 4 to 1 A little +/- 1% FS 5 to 18 High 10 to 1 Medium +/- 1% of rate 10 to 20 Medium