1 / 54

Industrial Instrumentation

Industrial Instrumentation. Dr. –Ing. Naveed Ramzan. Flow Sensors. Reasons for Flow Metering. Plant control, for product quality and safety reasons. Custody transfer, both interplant and selling to outside customers. Filling of containers, stock tanks and transporters.

andrew
Télécharger la présentation

Industrial Instrumentation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Industrial Instrumentation Dr. –Ing. Naveed Ramzan

  2. Flow Sensors

  3. Reasons for Flow Metering • 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.

  4. Types of Flow Meters • Differential Pressure Meters. • Rotary Meters. • Displacement • Inferential • New Flow Meters. • Electromagnetic • Vortex Shedding • Ultrasonic • Cross Correlation • Tracer • Swirl • Fluidic • Point Velocity Meters. • Mass Flow Maters.

  5. Differential Pressure Meters • Orifice Plate • Dall Tube • Venturi Tube • Pitot Tube • Rota meter • Target mater • Averaging Pitot • Nozzle • Spring Loaded • Intake Meter • Elbow Meter • Bypass Meter

  6. Parts of differential flow meters • 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.

  7. Parts of differential flow meters • 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.

  8. Obstruction Meters • Orifice Meters • Venturi Meters • Flow Nozzles

  9. Flow Through an Orifice Meter

  10. Flow Through an Orifice Meter P1 P2 d D P1 P

  11. 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 10k Re 0.85 5000 100k 0.6 b=d/D 0.1 0.8

  12. Obstruction Meters • Orifice Meters • Venturi Meters • Flow Nozzles

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

  14. Back to the Nozzle P1 P2 P1 P P2

  15. The Nozzle Flowmeter Shorter and cheaper than venturi But larger pressure drop. Thus, more power lost in operating. 0.98 C 0.86 105 103 Re

  16. Obstruction Meters • Orifice Meters • Venturi Meters • Flow Nozzles

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

  18. Flow through a Nozzle

  19. Flow through a Nozzle

  20. Flow through a Nozzle DP

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

  22. Differential Pressure Meters ( Cont‘d) Elbow Flow meter Rota meter

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

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

  25. Pitot Tube

  26. Rotary Meters ( Displacement Meters) Displacement Meters • Gear • Oval wheel • Vane Meter • Gear (Roots) • Diaphragm Meter • Liquid Sealed Meter Inferential Meters • Turbine Meter • Hoverflo Meter

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

  28. Types of Rotary Meters ( Displacement Meters) Types of Rotary Meters • Positive Displacement Rotary Meters • Inferential Rotary Meters

  29. PD Rotary Meters ( Displacement Meters) 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.

  30. PD Rotary Meters ( Displacement Meters) 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.

  31. PD Rotary Meters ( Displacement Meters) Principle of Operation • 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.

  32. PD Rotary Meters ( Displacement Meters) • Oval Gear • Nutating Disk • Oscillating Piston • Multi Piston • Rotating Impellers • Rotating Valve • Birotor • Roots Meter • Helix Meters

  33. PD Rotary Meters ( Displacement Meters) 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.

  34. PD Rotary Meters ( Displacement Meters) 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.

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

  36. PD Rotary Meters ( Displacement Meters) 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.

  37. PD Rotary Meters ( Displacement Meters) 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.

  38. PD Rotary Meters ( Displacement Meters) Rotating Impeller Birotor

  39. PD Rotary Meters ( Displacement Meters) 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 Advantages

  40. Rotary Meters ( Displacement Meters)

  41. PD Rotary Meters ( Displacement Meters) 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.

  42. PD Rotary Meters ( Displacement Meters) 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

  43. 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

  44. Inferential Meters • Turbine Meters • Paddle Wheel • Insertion Type 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

  45. Turbine Flow Meters

  46. Turbine Flow Meters • 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.

  47. Turbine Flow Meters • 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.

  48. Paddle Wheel Meters Paddle Wheel

  49. Inferential Meters 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 Disadvantages • High pressure drop that increases drastically with viscosity • Relatively high cost • Indirect measurement

  50. New Flow Meters • Electromagnetic EM Meter • Vortex Shedding Meter Vortex Generation Meter • Ultrasonic Flow Meters

More Related