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PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 1 Industrial Instrumentation Dr. –Ing. Naveed Ramzan

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Flow Sensors PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 2

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Plant control, for product quality and safety reasons. Custody transfer, both interplant and selling to outside customers. Filling of containers, stock tanks and transporters. Energy, mass balancing for costing purpose and health monitoring of heat exchangers. Health monitoring of pipelines and on-line analysis equipment, Government and company legislation may dictate the use here of such equipment. Reasons for Flow Metering PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 3

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Differential Pressure Meters. Rotary Meters. 1.Displacement 2.Inferential New Flow Meters. 1.Electromagnetic 2.Vortex Shedding 3.Ultrasonic 4.Cross Correlation 5.Tracer 6.Swirl 7.Fluidic Point Velocity Meters. Mass Flow Maters. Types of Flow Meters PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 4

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Orifice Plate Dall Tube Venturi Tube Pitot Tube Rota meter Target mater Averaging Pitot Nozzle Spring Loaded Intake Meter Elbow Meter Bypass Meter Differential Pressure Meters PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 5

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Parts of differential flow meters 1.Primary element (Part of meter used to restrict the fluid flow in pipe line to produce differential pressure) They include Orifice plate Venturi tubes Flow nozzles Pitot tube etc.

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1.Secondary element (measure the differential pressure produced by primary elements and convert them to usable forces or signals ) Secondary elements; Manometers Bellow meters Force balance meters etc. Parts of differential flow meters

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Obstruction Meters Orifice Meters Venturi Meters Flow Nozzles

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Flow Through an Orifice Meter

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P1P1 P2P2 P P1 d D

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Flow Through an Orifice Meter -Cheapest and Simplest -But biggest pressure drop and power lost (C~0.6 - 0.7) -Side Note: Pressure drop caused by friction and turbulence of shear layer downstream of vena contracta 0.6 0.85 =d/D 0.10.8 ReRe 100k 5000 10k

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Obstruction Meters Orifice Meters Venturi Meters Flow Nozzles

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Flow through a Venturi Meter In a venturi, 0.95 < C < 0.98 Advantage: Pressure recovery Uses little power

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Back to the Nozzle P1P1 P2P2 P P1P1 P2P2

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Shorter and cheaper than venturi But larger pressure drop. Thus, more power lost in operating. The Nozzle Flowmeter C 0.86 0.98 10 3 10 5 ReRe

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Obstruction Meters Orifice Meters Venturi Meters Flow Nozzles

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Flow through a Nozzle Basic Equations: a.) Continuity: mass in = mass out b.) Bernoullis Eqn. Total pressure is constant throughout

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Flow through a Nozzle

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P

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Y = Compressibility Factor =1 for incompressible flow or when P<< P abs C=Discharge Coefficient =f(Re) and nature of specific flow meter P Flow through a Nozzle P

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Elbow Flow meter Differential Pressure Meters ( Contd) Rota meter PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 22

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Rotameter, variable-area-flowmeter Force balance Drag Force Gravity Buoyancy (usually negligible) Derived on next slide

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For a fixed x-position, A is fixed. Then Rotameter Equations

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Pitot Tube

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Displacement Meters Gear Oval wheel Vane Meter Gear (Roots) Diaphragm Meter Liquid Sealed Meter Inferential Meters Rotary Meters ( Displacement Meters) Turbine Meter Hoverflo Meter PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 26

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Devices which are used to measure mass or volumetric flow rate of gas or liquid by using a rotating element. 14/01/2014 27 What are Rotary Meters ( Displacement Meters)

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Types of Rotary Meters Positive Displacement Rotary Meters Inferential Rotary Meters 14/01/2014 28 Types of Rotary Meters ( Displacement Meters)

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Positive displacement flow meters, also know as PD meters, measure volumes of fluid flowing through by counting repeatedly the filling and discharging of known fixed volumes. 14/01/2014 29 PD Rotary Meters ( Displacement Meters)

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Principle of Operation POSITION 1. As the bottom impeller rotates in a counterclockwise direction towards a horizontal position, fluid enters the space between the impeller and cylinder. POSITION 2. At the horizontal position, a definite volume of fluid is contained in the bottom compartment. 14/01/2014 30 PD Rotary Meters ( Displacement Meters)

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POSITION 3. As the impeller continues to turn, the volume of fluid is discharged out the other side. POSITION 4. The top impeller, rotating in opposite direction, has closed to its horizontal position confining another known and equal volume of fluid. 14/01/2014 31 Principle of Operation PD Rotary Meters ( Displacement Meters)

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Oval Gear Nutating Disk Oscillating Piston Multi Piston Rotating Impellers Rotating Valve Birotor Roots Meter Helix Meters 14/01/2014 32 PD Rotary Meters ( Displacement Meters)

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Nutating Disk A nutating disc meter has a round disc mounted on a spindle in a cylindrical chamber. By tracking the movements of the spindle, the flowmeter determines the number of times the chamber traps and empties fluid. 14/01/2014 33 PD Rotary Meters ( Displacement Meters)

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Oval Gear Two identical oval rotors mesh together by means of slots around the gear perimeter. The oval shaped gears are used to sweep out an exact volume of the liquid passing through the measurement chamber during each rotation. 14/01/2014 34 PD Rotary Meters ( Displacement Meters)

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Oval Gear The flow rate can be calculated by measuring the rotation speed. 14/01/2014 35 PD Rotary Meters ( Displacement Meters)

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Roots Meter The roots meter is similar in many respects to the oval gear meter. Two-lobed impellers rotate in opposite directions to each other within the body housing. 14/01/2014 36 PD Rotary Meters ( Displacement Meters)

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Roots Meter These peanut-shaped gears sweep out an exact volume of liquid passing through the measurement chamber during each rotation. The flow rate can be calculated by measuring the rotation speed. 14/01/2014 37 PD Rotary Meters ( Displacement Meters)

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Rotating Impeller 14/01/2014 38 PD Rotary Meters ( Displacement Meters) Birotor

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14/01/2014 39 Advantages High accuracy over a wide range of viscosities and flow rates up to 2000 cP with proper clearances. Extremely good repeatability on high viscosity fluids, very low slippage, long life if little or no abrasive material in the fluid Low pressure drop Functions without external power PD Rotary Meters ( Displacement Meters)

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Rotary Meters ( Displacement Meters) PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 40

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Advantages Special construction available for high viscosities and temperatures Can register near zero flow rate Measures directly, not an inferential device, for more consistent results Easy to repair and economical. 14/01/2014 41 PD Rotary Meters ( Displacement Meters)

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Disadvantages Increased maintenance compared to other meters, more moving parts May become damaged by flow surges and gas slugs Chance of corrosion and erosion from abrasive materials Derated flow rate capacity for high viscosities and temperatures Relatively high cost for large sizes 14/01/2014 42 PD Rotary Meters ( Displacement Meters)

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The inferential type meters are so-called because rather than measuring the actual volume of fluid passing through them, they infer the volume by measuring some other aspect of the fluid flow and calculating the volume based on the measurements 14/01/2014 43 Inferential Meters

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Turbine Meters Paddle Wheel Insertion Type 14/01/2014 44 Inferential Meters The inferential type meters are so-called because rather than measuring the actual volume of fluid passing through them, they infer the volume by measuring some other aspect of the fluid flow and calculating the volume based on the measurements

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Turbine Flow Meters PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 45

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It consists of a multi-bladed rotor mounted at right angles to the flow and suspended in the fluid stream on a free- running bearing. The diameter of the rotor is very slightly less than the inside diameter of the metering chamber, and its speed of rotation is proportional to the volumetric flow rate. 14/01/2014 46 Turbine Flow Meters

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The rotational speed is a direct function of flow rate and can be sensed by magnetic pick-up, photoelectric cell, or gears. Electrical pulses can be counted and totalized. 14/01/2014 47 Turbine Flow Meters

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Paddle Wheel 14/01/2014 48 Paddle Wheel Meters

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Advantages Very good repeatability Reduced susceptibility to fouling and deposits Less sensitive to viscosity changes Available in large sizes, good value for high flow rates Low maintenance Registers near zero flow rate 14/01/2014 49 High pressure drop that increases drastically with viscosity Relatively high cost Indirect measurement Disadvantages Inferential Meters

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Electromagnetic EM Meter Vortex Shedding Meter Vortex Generation Meter Ultrasonic Flow Meters New Flow Meters PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 50

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Magnetic Flowmeter New Flow Meters (Contd) PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 51

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Swirl Meter New Flow Meters (Contd) PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 52

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Coriolis Mass Flowmeter PEC – UET Lahore Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 53 In the Coriolis meter the fluid is passed through a tube. The tubes are available in different design like tubes of U-shape or horseshoe-shaped. The tubes can either be curved or straight. When two tubes are used the flow is divided when entering the meter and then recombined. The flow when enters the tube encounters oscillating excitation force that causes the tubes to vibrate at a fixed frequency. The vibration is induced in the direction that is perpendicular to flow of fluid. This creates the rotation frame of reference. Consider the tube during oscillation moving up and downward, when the tube is moving upward the fluid flowing in it tends to resist this and forces it downward. When the tube moves in the opposite direction, so does the fluid and a twist in introduced in the tube. All this might not be visible by directly observing. The twist at inlet of fluid and outlet of fluid results in phase difference or time lag and that is dependent on the fluid mass passing through the tube.

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Discussion & Questions? Dr. Shahid Naveed 14. Januar 2014 / Dr. –Ing Naveed Ramzan 54

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