TABLE OF CONTENTS Flow is measured by a number of different methods. This section will cover flow measurement made using the following types of flowmeters:
Differential Pressure
Magnetic
Mass Flow
Turbine
Open Channel
Vortex
Positive Displacement
Target
Thermal Mass
Tracer Dilution
Ultrasonic
Variable Area
Insertion
You should be familiar with the properties of liquids and gases when selecting, installing, calibrating and maintaining flowmeters. Some of the properties that effect accuracy and lifetime of flowmeters are:
Temperature
Pressure
Density
Specific
Gravity
Viscosity
Liquid State
Gaseous State
Vapor Pressure
Boiling Point
Electrical Conductivity
Sonic Conductivity
Specific Heat
Velocity
Flashing/Cavitating
Flow can be measured with direct or inferential devices. In most cases, flow is measured by the pressure drop developed across a flow device, such as an orifice plate, venture, or any specific restriction in a process flow line. Newer flow devices work on various physical or magnetic principles. The ISA Practical Guides Series volume, Flow Measurement, 2nd Edition, provides a complete description of all the various flow devices available today. Although flow is measured in many different ways, the following checklist will assist you in troubleshooting flow metering problems.
Selecting and using the proper flowmeter for your application will give you a more accurate reading of your process. The wrong flowmeter for your application will make controllability of the process harder, if not impossible.
Flowmeter installation must be performed correctly to achieve the stated performance of the flowmeter. The effects of improper installation vary...
