Series 270: Process Instrumentation
Course 275: Flow Measurement
Covers principles of fluid flow and how primary devices affect fluid flow. Describes flow measurement using several kinds of secondary devices. Discusses rotameters and other variable-area instruments. Explains how weirs, flumes, and other arrangements measure open-channel flow. Compares many kinds of positive-displacement meters and explains the operation of several kinds of turbine and magnetic flowmeters. Describes less-common flowmeters (including vortex-precession, mass flow, and ultrasonic devices) and instruments that meter the flow of solids. Provides guidelines for safe installation and maintenance of flow devices.
Lesson 1 - Properties of Fluid Flow
Topics:
Fluids in motion; Establishing a pressure difference; Indicating flow; Factors affecting flow rate; Reynolds number
Learning Objectives:
- Explain the difference between density and relative density (specific gravity).
- Define fluid velocity, viscosity, and volume flow rate.
- Describe laminar flow and turbulent flow.
- Explain how static head, friction head, and velocity head differ from each other.
- Explain how pipe size, pipe friction, and fluid viscosity affect the measurement of fluid flow.
Lesson 2 - Primary Measuring Devices
Topics:
Flow measurement in filled pipes; Restricting flow; Pressure drop; Orifice plates; Flow nozzles; Turndown and rangeability; Pipe taps
Learning Objectives:
- Describe direct and indirect flow measurement methods.
- Describe how a primary device creates a differential pressure.
- Give at least three examples of common primary devices and explain how each works.
- Describe the significant features of orifice plates and explain their functions.
- Discuss the conditions that determine the length of straight pipe required for each kind of primary flowmeter.
Lesson 3 - Secondary Measuring Devices
Topics:
Manometers; Liquid pressure measurement; Hazards of mercury; Bellows meter; DP transmitter; Target meter; Deadweight tester
Learning Objectives:
- Explain why both accuracy and precision are required in a secondary measuring device.
- Describe how an inclined manometer differs from a conventional U-tube manometer.
- Explain how to calibrate dry and wet manometers.
- Give examples of secondary measuring devices and explain how they work.
- Explain how to calibrate a differential pressure transmitter and discuss the different outputs available.
Lesson 4 - Variable-Area Instruments
Topics:
Rotameters; Measuring gas flow; Specific gravity, pressure, and temperature; Float and tube shapes; Piston, vane, and special meters
Learning Objectives:
- Discuss the similarities and differences between rotameters and orifice instruments.
- Compare the benefits of linear and nonlinear scales and explain how a square-root extractor is used.
- Explain how calibration, relative density, viscosity, and temperature affect rotameter readings.
- Describe how changes in the pressure, temperature, and relative density of a gas affect the ability of a rotameter to measure its flow rate.
- Discuss the operation of piston- and vane-type flowmeters and explain why armored rotameters and orifice-plug flowmeters are used.
Lesson 5 - Open-Channel Flow Devices
Topics:
The weir; Notch shapes; Weir precautions and maintenance; Using nomographs to calculate flow; Flume terminology and uses; Ultrasonic and capacitance level sensors
Learning Objectives:
- Describe the structure and function of a weir.
- Identify various weir components-notch, crest, pond, bulkhead, and head gauge.
- Describe the construction and function of a Parshall flume.
- Identify the parts of a Parshall flume-crest, throat, stilling well, and diverging and converging sections.
- Explain how ultrasonic and capacitance-level measuring devices are used to detect open-channel flow rates.
Lesson 6 - Positive-Displacement Meters
Topics:
Piston and rotating-vane meters; Nutating-disk, lobed impeller, oval, and helix flowmeters; Dry-gas bellows meter; Calibration
Learning Objectives:
- Describe the advantages and disadvantages of positive-displacement meters.
- Describe the operation of the reciprocating piston meter and the oscillating piston meter.
- Describe the operating principles of the sliding-vane rotary meter and the nutating-disk meter.
- Identify the elements in lobed impeller, oval, and helical flowmeters.
- Explain the operation of a dry-gas bellows meter.
- Discuss the calibration of positive-displacement meters.
Lesson 7 - Turbine and Magnetic Flowmeters
Topics:
Turbine flowmeter types, components, principles, construction, and installation; Magnetic flowmeter construction, output, and installation
Learning Objectives:
- Describe the operating principles governing turbine flowmeters.
- Discuss the construction of turbine flowmeters.
- Discuss the advantages and disadvantages of turbine flowmeters.
- Describe the operating principle governing magnetic flowmeters.
- Describe significant advantages and disadvantages of magnetic flowmeters.
Lesson 8 - Specialized Flowmeters
Topics:
Vortex-precession and vortex-shedding meters; Mass, thermal, and ultrasonic flowmeters; Heat-transfer, immersion-probe, and hot-wire meters
Learning Objectives:
- Discuss in detail the operation of a vortex-precession meter.
- Define the term vortex-shedding and describe vortex-shedding meters and their output system.
- Explain mass flow and describe a Coriolis meter.
- Describe three kinds of thermal flowmeters.
- Describe the Doppler-shift, beam-deflection, and frequency-difference methods used by ultrasonic flowmeters.
Lesson 9 - Metering the Flow of Solid Particles
Topics:
Volumetric and mass flowmeters for solids; Belt-type solids meters; Slurries; Constant-weight feeders
Learning Objectives:
- Define the term meter factor and explain how it is obtained.
- Explain the operation of a mass flowmeter.
- Discuss the operation of the belt-type solids meter.
- Describe how a slurry is made, transported, and metered.
- Discuss the continuous measurement and control of the flow of solid material in a process.
Lesson 10 - Installation and Maintenance of Flow Instruments
Topics:
Primary flow elements; Pressure taps; Piping, fittings, and valves; Electrical hookup; Maintenance precautions; Preventive maintenance; Calibration
Learning Objectives:
- Describe components of a differential flow measurement system.
- List guidelines for correct installation.
- Discuss the principles of thorough and safe instrument maintenance.
- List the steps in instrument calibration.
- Discuss the basic rules of safety in instrument servicing.
