flow_basics.ppt

Apr 11, 2023 1

BASICSOF

FLOW MEASUREMENT

Ranjan Bhattacharya Ujjal Roy RIL NMD

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What is Flow

• The motion characteristic of fluids (liquids or gases)

• Tyes of Flow: » Laminar Flow

» Turbulant Flow(RD < 2000) (RD > 4000)

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Flow Basics

Reynolds NumberV = Velocity D = Pipe Dia.µ = Viscosity = DensityRD < 2000 is Laminar Flow > 4000 is Turbulent Flow

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Flow Depends on

Velocity of Fluid

Friction of Fluid in contact with the pipe

Viscosity of fluid

Density of fluid ( In-turn Temperature for Fluid and Temperature & Pressure of the Gas)

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Types Of Flow meters Head Meters (Orifices, Venturi Tubes, Flow Tubes, and Flow

Nozzles, Pitot Tubes)

Vortex Flow meters

Turbine Flowmeters

Magnetic Flow Meters

Ultrasonic Flowmeters

Variable Area Flowmeters

Mass Flowmeters – Coriolis

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INITIAL STUDY FOR SELECTION OF FLOWMETERS

1) Identify all operating cases, such as operation at minimum, normal and maximum flow, alternative operating modes, start-up, commissioning and emergency operation.

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2) Determine the operating window

• Fluid data such as fluid name and phase, physical properties, special fluid

• aspects such as corrosiveness, erosiveness, toxicity and presence of solids or contaminants, special risks such as foaming, decomposition, fouling, plugging, depositing, solidification and chemical reaction.

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• Operating data such as flow rate, pressure, temperature, density and

viscosity.• Application aspects, such as

continuous/batch operation, pulsating flow, unidirectional or bi-directional flow, backflow risk, mechanical integrity,

• vibration and hydraulic noise.

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3 ) Collect data regarding the operating environment of the instrument. This should include the following aspects:

• Accessibility and physical location in relation to equipment and piping.

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• Mechanical integrity.

• Electrical safety and EMC requirements.

• Health, safety and environmental conditions.

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• Requirements of the plant organisation regarding maintenance, data collection and retrieval, self-diagnostic and documenting features, expertise and training etc.

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• Authority requirements: Instruments, instrument systems and components for installation in certain areas, equivalent local regulations and certification requirements may apply.

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Orifice Plate

Flange Taps Corner Taps Pipe Taps Vena Contracta Radius

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Orifice plate types

There are three types of orifice plates based on the position and shape of the hole on the plate

Concentric typeEccentric typeSegmental typel

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Use of Different types of plates

• Concentric sharp edge orifice plates are generally used for most of the applications

• Eccentric type orifice plates are used for fluids containing two phases.

• Quadrant edge orifice plates may be used for flow measurement where low Reynolds numbers are calculated

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Types of tapping

• Flange tapping• Corner tapping • Vena contracta tapping• Pipe tapping

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Orifices

General Technical Specifications :

Design Pressure: For plates it is limited by readout device and pipe design only.

Design Temperature: Function of associated readout system, only when the differential pressure unit must operate at the elevated temperature. For integral orifice transmitter the standard range is -29 to 121 °C.

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Materials of Const : There is no limitation on plate materials. Integral orifice transmitter wetted parts can be obtained in steel, stainless steel, Monel, nickel and Hastelloy.

Accuracy : ±0.25 to ±0.5% of actual flow. When a conventional d/p cell is used to detect the orifice differential, that will add a ±0.1 to ±0.3% of full scale error. The error contribution of ‘smart’ d/p cells is only 0.1% of actual span.

Rangeability The rangeability can approach 10:1

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Flange Tap

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Corner Tap

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Vena Contracta Taps

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Best design practices

• Square edge orifice plates with flange tappings, shall be used wherever possible. Only for special applications, e.g. due to low pipe Reynolds Number, should a quarter circle or a conical entrance plate be used.

• The calculated d/D ratio (Beta ratio) shall be within the limits of 0.2 and 0.7.

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• Eccentric orifice plates shall be used for fluids containing two phases. Eccentric orifice plates shall have the bottom of the orifice bore flush with the bottom I.D. of the pipe. Eccentric or segmental orifice plates shall be used on liquids containing large amounts of solid, or slurries

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• Each orifice plate shall be provided with a tab that is clearly visible in the final installed position.

• Differential pressure transmitters for gas services should be mounted such that they are self draining

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Venturi Tubes, Flow Tubes, and Flow Nozzles

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General Technical Specifications

Design Types:Design Types: A) Venturi TubesA) Venturi TubesB) Flow TubesB) Flow TubesC) Flow NozzlesC) Flow Nozzles

Design Pressure ratings:Design Pressure ratings: Usually limited only Usually limited only by the readout by the readout evice or by pipe pressure Design evice or by pipe pressure Design Temperature Limited only by a readout device, if Temperature Limited only by a readout device, if operation is at very operation is at very low or high temperature.low or high temperature.

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Sizes:Sizes: A) 1 in. (25 mm) up to 120 in. A) 1 in. (25 mm) up to 120 in. (3000 mm)(3000 mm)

B) 4 in. (100 mm) up to B) 4 in. (100 mm) up to 48 in. (1200 mm)48 in. (1200 mm)

C) 1 in. (25 mm) up to 60 in. C) 1 in. (25 mm) up to 60 in. (1500 mm)(1500 mm)

Fluids:Fluids: Liquids, gases, and steamLiquids, gases, and steam

Flow Range:Flow Range: Limited only by minimum and maximum Limited only by minimum and maximum beta (b) ratio and available pipe size rangebeta (b) ratio and available pipe size range

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Accuracy:Accuracy: Values given are for flow elements Values given are for flow elements only; d/p cell and readout errors are additional only; d/p cell and readout errors are additional

A)A) ±0.75% of rate uncalibrated, to ±0.25% ±0.75% of rate uncalibrated, to ±0.25% of of rate calibrated in a flow laboratory.rate calibrated in a flow laboratory.

B)B) May range from ±0.5 to ±3% of rate May range from ±0.5 to ±3% of rate depending upon the particular design and depending upon the particular design and variations in fluid operating conditions.variations in fluid operating conditions.

C)C) ±1% of rate uncalibrated to ±0.25% ±1% of rate uncalibrated to ±0.25% calibrated.calibrated.

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Construction MaterialsConstruction Materials:: Virtually Virtually unlimited. Cast venturi tubes are unlimited. Cast venturi tubes are generally cast iron, but fabricated venturi generally cast iron, but fabricated venturi

tubes can be made from carbon tubes can be made from carbon steel, most alloys available alloys, and steel, most alloys available alloys, and fiberglass plastic composites. Flow fiberglass plastic composites. Flow nozzles are nozzles are commonly made from alloy commonly made from alloy steel and stainless steel.steel and stainless steel.

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Reynolds Number:Reynolds Number: Venturi and flow tube Venturi and flow tube discharge coefficients are constant at Re > discharge coefficients are constant at Re > 100,000. Flow nozzles are used at high 100,000. Flow nozzles are used at high pipeline velocities (100 ft/s or 30.5 m/s), pipeline velocities (100 ft/s or 30.5 m/s), usually usually Corresponding to Re > 5 million. Corresponding to Re > 5 million.

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Pitot Tubes - Anubar

The point velocity of approach (VP) can be calculated by taking the square root of the difference between the total pressure (PT) and the static pressure (P) and multiplying that by the C/D ratio, where C is a dimensional constantand D is density:VP = C(PT - P)H /D

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Pitot Tube

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Pitot Tube

• Pitot tubes utilize the principles captured in Bernoulli.s equation, to measure flow.

• Most pitot tubes actually consist of two tubes. One, the low pressure tube measures the static pressure in the pipe. The second, the high pressure tube is inserted in the pipe in such a way that the flowing fluid is stopped in the tube. The pressure in the high-pressure tube will be the static

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Disadvantage

• The pressure differential is usually small and hard to measure.

• The differing flow velocities across the pipe make the accuracy dependent

on the flow profile of the fluid and the position of the pitot in the pipe.

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Annubar

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Annubar

• An annubar is very similar to a pitot tube. The difference is that there is more than one hole into the pressure measuring chambers.

• The pressure in the high-pressure chamber represents an average of the velocity across the

pipe. Annubars are more accurate than pitots as they are not as positionsensitive or as sensitive to the velocity profile of the fluid.

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Problems

• Erosion• Particulate, suspended solids or debris in the

piping will not only plug up the sensing lines, it will erode the sensing device. The orifice, by its design with a thin, sharp edge is most affected, but the flow nozzle and even venturi can also be damaged. As the material wears away, the differential pressure between the high and low sides of the sensor will drop and the flow readingwill decrease.

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Problems

• Over ranging Damage to the D/P Cell

pressures are usually much greater than the differential pressure and three valve manifolds must becorrectly used.

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• Vapour Formation in the Throat D/P flow sensors operate on the relation between

velocity and pressure. As gas requires less pressure to compress, there is a greater pressure differential

across the D/P cell when the gas expands on the LP side of the sensor.

The flow sensor will indicate a higher flow rate than there actually is. The turbulence created at the LP side of the sensor will also make the readingsomewhat unstable. A small amount of gas or vapour will make a large difference in the indicated flow rate.

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Problems

The opposite can occur if the vapour forms in the HP side of the sensor due to cavitation or gas pockets when the fluid approaches the boiling point. In such an instance there will be a fluctuating pressure drop across the D/P cell that will give an erroneously low (or even negative) D/P reading

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Problems

• Plugged or Leaking Sensing Lines• The instrument error will depend on where the plug/leak is:• On the HP side a plugged or leaking sensing line

will cause a lower reading.• The reading will become irrational if the LP

pressure equals or exceeds the HP sensing pressure.

• On the LP side a plugged or leaking sensing line will cause a higher reading.

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Temperature and pressure Compensation

• Due to the basic property of gas we need to correct the Flow value for operating condition Temperature and pressure

• This is called Compensation • This is calculated by general gas

equation P0V0/T0 = P1V1/T1• Where P0 & V0 are design pressure and

temperatures and P1/T1 are actual pressure and temperature .

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Vortex Flow Meter

As Vortex is shed from one side of bluff body, the fluid velocity on thatside increases & pressure decreases

On the other side velocity decreases& pressure increases thus causingnet pressure change across bluff body

Frequency at which vorticesare formed is directly proportionalto velocity of fluid.

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Types:Types: VortexVortex

Services:Services: Gas, steam, clean liquidsGas, steam, clean liquids

Size Ranges Available:Size Ranges Available: 0.5 to 12 in. (13 to 300 mm), also probes0.5 to 12 in. (13 to 300 mm), also probes

Flow Velocity Range:Flow Velocity Range: Liquids 1 to 33 ft/s (0.3 to 10 m/s)Liquids 1 to 33 ft/s (0.3 to 10 m/s)

Minimum Reynolds No.:Minimum Reynolds No.: Under Re of 8000 to 10,000, Under Re of 8000 to 10,000, meters do not function at all; meters do not function at all;

for best performance Re for best performance Re should exceed 20,000 in sizes should exceed 20,000 in sizes under 4 in. (100 mm) and under 4 in. (100 mm) and

exceed 40,000 in sizes above 4 in.exceed 40,000 in sizes above 4 in.


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Output Signals:Output Signals: Linear pulses or analogLinear pulses or analog

Design Pressure:Design Pressure: 2000 PSIG (138 bars)2000 PSIG (138 bars)

Design Temperature:Design Temperature: -201 to 400°C-201 to 400°C

Materials of Construction:Materials of Construction: Mostly stainless steel, Carbon steel.Mostly stainless steel, Carbon steel.

Rangeability:Rangeability: Reynolds number at maximum flow Reynolds number at maximum flow divided by minimum Re of 20,000 or divided by minimum Re of 20,000 or more 40:1more 40:1

Accuracy:Accuracy: 0.5 to 1% of rate for liquids. 1 to 0.5 to 1% of rate for liquids. 1 to 1.5% of rate for gases and steam 1.5% of rate for gases and steam

with pulse outputs; for analog with pulse outputs; for analog outputs add 0.1% of full scaleoutputs add 0.1% of full scale


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Best design Practices

• Due to velocity cut-off requirement meter may be sized lower than the pipe size

• The maximum flow to be measured should not be less than 35% of the maximum measurable flow rate (the capacity) of the chosen vortex meter

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• Vortex meters will only function properly under truly single-phase fluid conditions.

• In liquid applications, the pressure profile across the vortex meter shall not result in cavitation under any operating condition. Cavitation will cause signal drop-out and might damage the meter and downstream piping

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• Vortex meters should not be located downstream of positive displacement

pumps/compressors without suction and discharge dampers.

• Vortex flow meters should not be used in wet gas or wet steam applications or in any other two-phase application (e.g. liquids with gas bubbles or foam, flashing liquids, half-full lines)

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• Vortex flow meters should not be considered for very viscous, waxy or erosive services.

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Turbine Flow Meter

Consist of multi-bladed rotor assembly suspended in fluid stream on free running bearing. Fluid impinging on rotor blade causes rotor to revolve Angular speed of rotation is directly proportional to volumetric flow rate Speed of rotation is monitored by magnetic pick-up

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Type:Type: Turbine FlowmetersTurbine Flowmeters

Service:Service: Relatively clean liquids, gases, and vapours.Relatively clean liquids, gases, and vapours.

Sizes:Sizes: 3/16 to 24 in. (5 to 610 mm) in flow through 3/16 to 24 in. (5 to 610 mm) in flow through designs.designs.

Outputs:Outputs: Generally linear frequency outputs are provided, Generally linear frequency outputs are provided, but 4 to 20 mA DC can also be obtained through but 4 to 20 mA DC can also be obtained through

conversion.conversion.

Operating Pressure:Operating Pressure: 1500 PSIG (10.3 MPa) in standard and 5000 PSIG 1500 PSIG (10.3 MPa) in standard and 5000 PSIG (34.5 MPa) in special designs.(34.5 MPa) in special designs.

Pressure Drops:Pressure Drops: Usually one velocity head or about 3 to 5 PSIG (20 Usually one velocity head or about 3 to 5 PSIG (20 to 35 kPa) Negligible.to 35 kPa) Negligible.

Operating Temp.:Operating Temp.: -50 to 150°C in standard and -200 to 450°C in -50 to 150°C in standard and -200 to 450°C in extended pickup designs.extended pickup designs.


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Material of Construction:Material of Construction: Normally stainless Normally stainless steel housing and rotor with tungsten carbide steel housing and rotor with tungsten carbide sleeve bearings, but Hastelloy C or other housing sleeve bearings, but Hastelloy C or other housing materials and ceramic or PTFE bearings are also materials and ceramic or PTFE bearings are also available.available.

Accuracy:Accuracy: Linearity is 0.25% of actual flow Linearity is 0.25% of actual flow for for turbine meters larger than ¾ in. turbine meters larger than ¾ in.

and 0.5% for smaller and 0.5% for smaller units. units.

Rangeability:Rangeability: 10 : 1 unless limited by use of 10 : 1 unless limited by use of line-size line-size units or high process fluid units or high process fluid viscosity.viscosity.


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Magnetic Flow meter

Faraday’s Law: When a current carrying conductor is placed in a magnetic field,an emf (E) is induced in it.

E = kBDV

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Magnetic Flow meter

Two types of excitation - AC Type Apply Line voltage to Coil. Signal generated

will be high Milivolt to Low milivolt range.-Pulsed DC: In this design magnetic coils are periodically

energized.

When coils are energized induced voltage is result of noise & signal.

When coils are not energized induced voltage is result of noise.

Subtraction of these two induced voltages yield signal only.

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General Technical SpecificationsDesign Pressure:Design Pressure: Depends on pipe size, e.g. for a 4” (100 mm) Depends on pipe size, e.g. for a 4” (100 mm)

unit, the maximum is 20 bars. Special units are unit, the maximum is 20 bars. Special units are available with pressure ratings upto 172 bars.available with pressure ratings upto 172 bars.

Design Temperature:Design Temperature: Upto 120°C with Teflon liners; Upto 180°C with Upto 120°C with Teflon liners; Upto 180°C with Ceramic Ceramic liners.liners.

MOC Liners:MOC Liners: Ceramics, fiber glass, neoprene, polyurethene, Ceramics, fiber glass, neoprene, polyurethene, rubber, Teflon,kynar.rubber, Teflon,kynar.

Electrodes:Electrodes: Alloy20, Hastelloy C, SS, Tantalum, Ti, Tungsten Alloy20, Hastelloy C, SS, Tantalum, Ti, Tungsten carbide, Monel, Ni, Pt-Alumina Ceramic.carbide, Monel, Ni, Pt-Alumina Ceramic.

Type of flow detected:Type of flow detected: Volumetric flow of conductive liquids, including Volumetric flow of conductive liquids, including slurries of corrosive or abrasive materials.slurries of corrosive or abrasive materials.

Rangeability:Rangeability: 30:130:1

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Min. Conductivity:Min. Conductivity: 20 microsiemens/cm. Special design can operate at 20 microsiemens/cm. Special design can operate at 0.05 Required or 0.1 ms/cm.0.05 Required or 0.1 ms/cm.

Flow Ranges:Flow Ranges: 0.01 to 100000 GPM (0.04 to 378000 l/m)0.01 to 100000 GPM (0.04 to 378000 l/m)

Size Ranges:Size Ranges: From 0.1 to 96” in diameterFrom 0.1 to 96” in diameter

Velocity Ranges:Velocity Ranges: 0 - 0.1 to 0 - 10 m/s0 - 0.1 to 0 - 10 m/s

Accuracy:Accuracy: ±1% of full scale for AC excitation.±1% of full scale for AC excitation.±1% of actual flow for 10:1 range and±1% of actual flow for 10:1 range and±0.5% of actual flow for 2:1 or 5:1 range.±0.5% of actual flow for 2:1 or 5:1 range.


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1)1) Conductivity of the liquid.Conductivity of the liquid.

2)2) Effect of liquid operating temperature upon the threshold conductivity of the Effect of liquid operating temperature upon the threshold conductivity of the liquid.liquid.

3)3) Magnetic flowmeter must always be full to assure accurate measurement.Magnetic flowmeter must always be full to assure accurate measurement.

4)4) Liquid should not contain entrained gases.Liquid should not contain entrained gases.

5)5) The meters electrodes must remain in electrical contact with the fluid being The meters electrodes must remain in electrical contact with the fluid being measured and should always be installed in the horizontal plane.measured and should always be installed in the horizontal plane.

6)6) Periodic cleaning is required if build-up is there.Periodic cleaning is required if build-up is there.

7)7) Temperature limitation of a particular lining material to be considered.Temperature limitation of a particular lining material to be considered.

Application Criteria

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• Electromagnetic flow meters are suitable for most liquids, provided they are electrically conductive. Electromagnetic flow meters are not suitable for gas and steam applications

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• Avoid installation of electromagnetic flow meters close to large conducting surfaces such as metal supports. These large metal objects will interfere with the magnetic field

of the flow meter and hence influence its accuracy and behaviour

• Liner material should be properly selected based on Service

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• Electromagnetic flow meters shall be used for dirty and greasy fluids, untreated sewage and fluids containing solids where orifice plates cannot be used.

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• Since most hydrocarbons have a very low conductivity, electromagnetic flow meters are mainly used in utility services and chemical plants.

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Advantage

• Not affected by Physical Properties such as Pressure , temperature etc .

• No moving parts

• Short straight run requirement

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Limitations

• Only Conductive liquids can be measured

• Limitation for use in high Temperature & pressure

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Positive DisplacementFlow Meter

Positive displacement meters split the flow of liquid into separate known volumes based on physical dimension of meter & count them.

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Type: A) Oval GearB) Nutating DiscC) Rotating Vane type

Design Pressure: Up to 1500 PSIG (103.42 Bars)

Design Temperature: 204 °C

MOC: Bronze , Cast Iron , Aluminium , Steel , SS , Hastelloy , Monel.

Service: Clean liquid

Range: 0.01 GPM to 20000 GPM

Accuracy: 0.1% to 2% of Flow

Rangeability: 15:1

Strainer Required: Yes (Cannot handle Solids > 100 micron)


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Advantage

• High Accuracy

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Limitation

• Sensitive to over-load

• Pressure Loss

• Pipe Blockage in case of Mechanical Failure

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Ultrasonic Flow Meter

Transit time measurement

Doppler frequency measurement

Measures flow by measuring the time taken for ultrasonic energy to traverse a pipe section, both with & against the flow of liquid with in pipe.

Ultrasonic energy is projected at angle trough pipe wall into liquid. Part of energy is reflected by bubbles or particles in liquid & returned to receiving crystal.Since reflectors are traveling at fluid velocity, the frequency of the reflected wave is shifted according to Doppler principle.

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Type:Type: A) A) Transit timeTransit time

B)B) Reflection -Doppler frequency shift or multi- Reflection -Doppler frequency shift or multi- pulse time shift.pulse time shift.

(Note : A and B can be either ‘wetted’ or (Note : A and B can be either ‘wetted’ or ‘clamp-on’. Type A is more often wetted; ‘clamp-on’. Type A is more often wetted; type B is more often clamp-on. Clamp-on type B is more often clamp-on. Clamp-on designs cannot be as easily used on concrete designs cannot be as easily used on concrete

or lined metal pipe as on ordinary metal pipe. or lined metal pipe as on ordinary metal pipe.

Applications:Applications: A) A) Clean liquids with little or no solids or Clean liquids with little or no solids or bubbles; gases.bubbles; gases.

B) B) Slurries with solids (0.2 to 60% Slurries with solids (0.2 to 60% concentration, depending upon particle size), concentration, depending upon particle size),

liquids that are aerated or contain bubbles, liquids that are aerated or contain bubbles, gases with sound reflecting particles; single gases with sound reflecting particles; single phase turbulent clean liquid.phase turbulent clean liquid.


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Flow Velocity Range:Flow Velocity Range: A) 1 to 100 ft/s (0.3 to 30m/s).A) 1 to 100 ft/s (0.3 to 30m/s).

B) Minimum velocity for solids to stay in B) Minimum velocity for solids to stay in suspension is about 2.5 ft/s (0.75 m/s); suspension is about 2.5 ft/s (0.75 m/s);

bubbles require 6 ft/s (1.8 m/s). bubbles require 6 ft/s (1.8 m/s). Otherwise, 0.2 to 60 ft/s (0.06 to 18 Otherwise, 0.2 to 60 ft/s (0.06 to 18

m/s) m/s)

Process Temperature:Process Temperature: A) & B) -184 to 260°C; higher or lower A) & B) -184 to 260°C; higher or lower with special sound transmitting wedges.with special sound transmitting wedges.

Design Pressure:Design Pressure: A) Up to 1000 PSIG A) Up to 1000 PSIG B) Unlimited for clamp-on.B) Unlimited for clamp-on.

Construction Materials:Construction Materials: A) Spools or transducer probes can be A) Spools or transducer probes can be steel, stainless steel or alloys.steel, stainless steel or alloys.

B) Process pipe it conducts ultrasonic B) Process pipe it conducts ultrasonic energy.energy.

Sizes:Sizes: A) 0.125 to 120 in. (3 mm to 3 m) diaA) 0.125 to 120 in. (3 mm to 3 m) diaB) 0.5 to 72 in. (13 mm to 1.8 m) diaB) 0.5 to 72 in. (13 mm to 1.8 m) dia


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Straight Pipe Required:Straight Pipe Required: A) & B) 10 to 20 diameters A) & B) 10 to 20 diameters upstream, 5 downstream; upstream, 5 downstream;

very disturbed profiles require very disturbed profiles require even longer straight runs or flow even longer straight runs or flow

straightners.straightners.

Accuracy:Accuracy: A) From 1% of actual flow to 2% A) From 1% of actual flow to 2% of full scale. Error can be reduced of full scale. Error can be reduced

by careful determination of pipe by careful determination of pipe ID ID and by increasing and by increasing number of number of paths.paths.

B) 2 to 5% of full scale.B) 2 to 5% of full scale.


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• Ultrasonic flow meters shall be considered for use on large lines (≥ 18”) and for large turn downs and where pressure drop is not permitted

• Only ultrasonic flow meters based on the “time-of-flight” method shall be used. Meters based on the “Doppler” principle are less accurate and is not advisable .

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• Care shall be taken if an ultrasonic flow meter and a low noise control valve are installed in the same pipe.

• Certain high frequencies produced by a low noise control valve may interfere with the measuring signals of the ultrasonic flow meter. A special silencer may have to be installed between the meter and this type of control valve.

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Advantages

• Can be used for very large diameters

• No pressure Loss

• Not dependent on Physical Properties

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Limitations

• Average accuracy

• Dependent on flow-profile

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Variable Area Flow Meter

When fluid enters metering tube, the buoyant effect of the fluid lightens the floatBut it has greater density than the fluid & buoyant effect is sufficient to raise it.As there is small annular opening between float & metering tube, pressure drop across the float increases & raises the float to increase annular area.Float raises till upward hydraulic forces are balance by weight less the buoyant forces.

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Type:Type: Rotameter (float in tapered tube)Rotameter (float in tapered tube)

Standard Design Pressure:Standard Design Pressure: 350 PSIG (2.4 MPa) average maximum for 350 PSIG (2.4 MPa) average maximum for glass metering tubes, dependent on size. glass metering tubes, dependent on size. Upto 720 PSIG (5 MPa) for metal tubes Upto 720 PSIG (5 MPa) for metal tubes

and special designs to 6000 PSIG (41 and special designs to 6000 PSIG (41 MPa)MPa)

Standard Design Temperature:Standard Design Temperature: Upto 204°C for glass tubes and upto Upto 204°C for glass tubes and upto 538°C for some models of metal tube 538°C for some models of metal tube

meters.meters.

End Connections:End Connections: Female Pipe thread or flangedFemale Pipe thread or flanged

Fluids:Fluids: Liquids, gases, and vaporsLiquids, gases, and vapors

Accuracy:Accuracy: Laboratory rotameters can be accurate to Laboratory rotameters can be accurate to ±½% of actual flow; most industrial ±½% of actual flow; most industrial

rotameters will perform within ±1 to 2% of rotameters will perform within ±1 to 2% of full scale over a 10:1 range, and purge or full scale over a 10:1 range, and purge or by pass meters, ±5 to 10% of full range.by pass meters, ±5 to 10% of full range.


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MOC:MOC: Tube:Tube: Borosilicate glass, stainless steel, Borosilicate glass, stainless steel, Hastelloy, Monel, Alloy 20. Hastelloy, Monel, Alloy 20.

Float:Float: Conventional type - brass, Conventional type - brass, stainless steel, Hastelloy, Monel, Alloy 20, stainless steel, Hastelloy, Monel, Alloy 20, nickel, titanium, or tantalum, and special nickel, titanium, or tantalum, and special plastic floats. Ball type - glass, stainless plastic floats. Ball type - glass, stainless

steel, tungsten carbide, sapphire, or steel, tungsten carbide, sapphire, or tantalum.tantalum.

End Fittings:End Fittings: Brass, stainless steel, or Brass, stainless steel, or alloys for corrosive fluids.alloys for corrosive fluids.

Packing:Packing: The generally available The generally available elastomers are used and O-rings of elastomers are used and O-rings of

commercially available materials; Teflon is commercially available materials; Teflon is also available.also available.


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Mass Flow Meter - Coriolis

m/t = /r2m = Mass= Torquer= radious of gyration.= angular velocity.

Sensor tube is driven by magnetic coil & it vibrates similar to tuning fork. Fluid flowing inside the tube pushes down the tube & fluid flowing outside tube pushes tube up words. This twisting characteristics is called Coriolis effect. As per Newton's second law of angular motion, amount of sensor twist is proportional to mass flow

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OPERATING PRINCIPLE

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Size:Size: 1/16 to 6”1/16 to 6”

Flow Range:Flow Range: 0 to 11,340 Kg/m0 to 11,340 Kg/m

Fluids:Fluids: Liquids, slurries, compressed gasesLiquids, slurries, compressed gases

Output Signal:Output Signal: Linear frequency, analog, digital, scaled pulse Linear frequency, analog, digital, scaled pulse displaydisplay

Detector Types:Detector Types: Electromagnetic, optical, capacitiveElectromagnetic, optical, capacitive


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Operating Pressure:Operating Pressure: Depends upon size flange rating: 124 bars typical Depends upon size flange rating: 124 bars typical standard; 345 bars typical high pressurestandard; 345 bars typical high pressure

Pressure Drop:Pressure Drop: 0.7 bars to 6.9 bars as a function of viscosity and 0.7 bars to 6.9 bars as a function of viscosity and designdesign

Operating Temp.:Operating Temp.: 73 to 204 °C typical standard; 0 - 426 °C high 73 to 204 °C typical standard; 0 - 426 °C high temperaturetemperature

MOC:MOC: SS, Hastelloy, Ti;SS, Hastelloy, Ti;

Accuracy:Accuracy: ±0.15 to 0.5% of rate±0.15 to 0.5% of rate

Repeatability:Repeatability: ±0.05 to ±0.2% of rate±0.05 to ±0.2% of rate

Rangeability:Rangeability: 10:1 calibration range (typical)10:1 calibration range (typical)


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1.1. The operation of the flowmeter is independent of Reynolds number, The operation of the flowmeter is independent of Reynolds number, therefore, extremely viscous fluids can also be measured. therefore, extremely viscous fluids can also be measured.

2.2. Coriolis flowmeters provide a direct mass flow measurement without the Coriolis flowmeters provide a direct mass flow measurement without the addition of external measurement instruments. addition of external measurement instruments.

3.3. Coriolis flowmeters have outstanding accuracy. The base accuracy is Coriolis flowmeters have outstanding accuracy. The base accuracy is usually on the order of 0.2%. In addition, the flowmeters are extremely usually on the order of 0.2%. In addition, the flowmeters are extremely linear over their entire flow range.linear over their entire flow range.

4.4. The rangeability of the flowmeters is usually on the order of 20:1 or greater. The rangeability of the flowmeters is usually on the order of 20:1 or greater. Coriolis flowmeters have been successfully applied at flow rates 100 times Coriolis flowmeters have been successfully applied at flow rates 100 times lower than their rated full scale flow rate.lower than their rated full scale flow rate.

5.5. A Coriolis flowmeter is capable of measuring mass flow rate, volumetric A Coriolis flowmeter is capable of measuring mass flow rate, volumetric flow rate, fluid density and temperature - all from one instrument.flow rate, fluid density and temperature - all from one instrument.

Advantages

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6.6. The operation of the flowmeter is independent of flow characteristics such The operation of the flowmeter is independent of flow characteristics such as turbulence and flow profile. Therefore upstream and downstream straight as turbulence and flow profile. Therefore upstream and downstream straight run requirements and flow conditioning are not necessary. They can also be run requirements and flow conditioning are not necessary. They can also be used in installations that have pulsating flow.used in installations that have pulsating flow.

7.7. Coriolis flowmeters do not have internal obstructions which can be Coriolis flowmeters do not have internal obstructions which can be damaged or plugged by slurries or other type of particulate matter in the damaged or plugged by slurries or other type of particulate matter in the flow stream. Entrained gas or slugs of gas in the liquid will not damage the flow stream. Entrained gas or slugs of gas in the liquid will not damage the flowmeter. There are no moving parts which will wear out and require flowmeter. There are no moving parts which will wear out and require replacement. These design features reduce the need for routine replacement. These design features reduce the need for routine maintenance.maintenance.

8.8. The flowmeter can be configured to measure flow in either the forward or The flowmeter can be configured to measure flow in either the forward or the reverse direction. In reverse flow there will still be a time or phase the reverse direction. In reverse flow there will still be a time or phase difference between the flow detector signals, but the relative difference difference between the flow detector signals, but the relative difference between the two detector signals will be reversed.between the two detector signals will be reversed.

Advantages

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1.1. Coriolis flowmeters are not available for large pipelines. The largest Coriolis Coriolis flowmeters are not available for large pipelines. The largest Coriolis flowmeter that is currently available has a maximum flow rating of 25,000 lb/min. flowmeter that is currently available has a maximum flow rating of 25,000 lb/min. (11,340 kg/min.) and is equipped with 6 inch (15 cms) flanges. When larger flow (11,340 kg/min.) and is equipped with 6 inch (15 cms) flanges. When larger flow rates must be measured, two or more flowmeters mounted in parallel are required.rates must be measured, two or more flowmeters mounted in parallel are required.

2.2. Some flowmeter designs require extremely high fluid velocities in order to achieve a Some flowmeter designs require extremely high fluid velocities in order to achieve a significant amount of time or phase difference between the flow detector signals. This significant amount of time or phase difference between the flow detector signals. This can result is extremely high pressure drops across the flowmeter.can result is extremely high pressure drops across the flowmeter.

3.3. Coriolis flowmeters are expensive. However, the cost of a Coriolis flowmeter is often Coriolis flowmeters are expensive. However, the cost of a Coriolis flowmeter is often comparable to (or below) the cost of a volumetric meter plus a densitometer used comparable to (or below) the cost of a volumetric meter plus a densitometer used together to determine the mass flow rate.together to determine the mass flow rate.

4.4. Coriolis flowmeters have difficulty measuring the flow rate of low pressure gas. Coriolis flowmeters have difficulty measuring the flow rate of low pressure gas. Applications with pressure less than 150 psig. are marginal with the flowmeter Applications with pressure less than 150 psig. are marginal with the flowmeter designs that are currently available. Low pressure gases have low density and their designs that are currently available. Low pressure gases have low density and their mass flow rate is usually very low. In order to generate enough mass flow rate to mass flow rate is usually very low. In order to generate enough mass flow rate to provide sufficient Coriolis force to be measured, the gas velocity must be extremely provide sufficient Coriolis force to be measured, the gas velocity must be extremely high. This in turn may lead to prohibitively high pressure drops across the meter.high. This in turn may lead to prohibitively high pressure drops across the meter.

Limitations

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Best design Practices

• Avoid the use of Coriolis mass flow meters in two-phase fluids. The presence of a small amount of gas in liquids or liquid in gas will create erratic measurements.

• The flow meter shall be properly supported as specified by the Supplier. The meter will only measure properly if it is installed vibration and stress free in the pipe work.

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• As Coriolis mass flow meters have no moving parts and in general do not require accessories like strainers, gas eliminators or flow straighteners, they should be used in preference to positive displacement meters and turbine meters.

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Mass Flow Meter- Thermal

Q = WCp(T2-T1)Q = Heat TransferredW = Mass flow rate of fluidCp = Specific heat of fluidT1 = Temp of fluid before heat transferred.T2 = Temp of fluid after heat has been transferred.

Heat is added to fluid stream with electric immersion heater.Power to heater equals heat transferred to fluid (Q) & is measured by wattmeter.T1, T2 are thermocouple or RTD.Since we know measuring fluid we know Cp.By measuring T1, T2 & Q we can calculate flow rate-W.

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Operating Principle

• Inside the flow meter sensor head, a heated resistance thermometer (RTD) is electronically compared with an unheated RTD sensor.

• As a gas passes the heated RTD, heat is transferred from this sensor to the gas,and hence the RTD is cooled, thereby reducing the temperature difference between the two sensors.

• Heat transfer from the RTD to the process gas depends on the composition of the gas, hence the temperature difference between the two RTDs is a function of themass flow rate of the gas

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Limitations :The temperature and the sensor must protrude into the fluid stream. Thus, these

components (particularly the heater) are easily damaged by corrosion and erosion. Further more, the integrity of the piping is sacrificed by the protrusion into the fluid stream, increasing danger of leakage. As an alternative, the heater and the upstream and downstream temperature sensors can be mounted outside of the piping

Application :The thermal conductivity and the specific heat of the process fluid must be

constant. These types of flowmeters are best suited for measurement of homogeneous gases and are not recommended for applications where the process fluid composition or moisture content are variable.

Limitation and application

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General Technical Specifications :

Types : Heat transfer type mass flowmeters.

Design Temperature : Upto 232 °C, higher with special designs.

Design Pressure : A) Upto 83 bars, higher with special designs.

B) Low pressure design upto 1 bar, others upto 69 bars.

Pressure Drop : Usually only a few inches of water.

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Process Fluids : Gases and liquids.

Flow Range : Maximum 18,000 Kg/hr.

Accuracy : ± 1% to ± 2% of full scale.

Rangeability : 10:1

MOC : SS, glass, Teflon, Monel, etc.

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Custody Transfer or Fiscal Metering

When fluid is to be traded between two parties, accurate measurement of fluid passing through

pipelines is required to make fare transactions.This measurement is termed as custody transfer or fiscal flow measurement.

Fiscal metering is done with four types of meters-PD, Ultrasonic, Mass, Turbine.

Custody transfer meters validation (Proving) isRequired-Gravimetric-Volumetric-Master Meter

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FLOWMETER SELECTION GUIDEFlowmeter

Element

Recommended Service

Rangebility

Pressure Loss

Accuracy % Req upstream/downstream St. Pipe length

Viscosity

Effects

Realtive Cost

ORIFICE Clean liquids, gas, vapor

4 to 1 Medium +/- 0.5 to 2 of FS

20/5 High Low

FLOW NOZZLE Clean,dirty liquids 4 to 1 Medium +/- 1 to 2 of FS 20/5 High Medium

PITOT TUBE Clean liquids, Gas, Steam

4 to1 Very low +/- 3 to 5 of FS 40/10 Low Low

VARIABLE AREA METER

Clean,dirty viscous liquids

10 to 1 Medium +/- 1 to 10 of FS

None Low Low

TURBINE Clean, viscous liquids

10 to 1 High +/- 0. 25 of rate

10/5 High High

VORTEX Clean,dirty liquids, Gas, steam

40 to 1 Medium +/- 1 of rate 15/5 Medium High

EMF Clean,dirty,viscous conductive liquids & slurries

30 to 1 None +/- 0.5 % of rate

5/3 None High

ULTRASONIC Clean, viscous liquids

10 to 1 None +/- 1 to 3 of FS 15/5 None High

MASSFLOW Clean,dirty,viscous liquids & slurries

10 to 1 Low +/- 0.4 % of rate

None None High

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THANK YOU…

Documents

flow_basics.ppt