The industry's most authoritative handbook on flow measurement provides a road map to the field of flow measurement. This best-seller discusses strategies for problem solving and puts the whole array of types of flowmeters at the reader's disposal. The text includes laminar flow elements, critical flowmeters, statistics for measurement, laboratory primary standards, and uncertainty in flow measurement. Emphasis is placed on the importance of accuracy in measurements and ways of ensuring accuracy and avoiding equipment damage through correct forecast of operating conditions, flowmeter selection, installation, calibration, and maintenance. Fundamental considerations such as mixed-phase flow, piping effects, and flow conditioning are examined at length. The problem of attaining a meaningful flow signal through linearization, compensation, and totalization is discussed. Join the thousands of engineers, technicians, managers, and salespeople that have found this reference text an invaluable resource.
TABLE OF CONTENTS Chapter 12 - Mass Flowmeters
| Flowmeters that measure mass directly using the properties of mass, as opposed to those that measure volume or velocity, were developed and commercialized in the 1980s. Meters of this type have found wide application because the fluid measurement is virtually independent of changing fluid parameters. Many of the other flowmeter technologies are affected by changes in fluid density, viscosity, pressure, and/or temperature. Meters that measure mass directly, in effect, weigh the fluid as it passes through the meter, yielding a highly accurate measurement that is virtually independent of varying process conditions that often occur. Because of this unique ability, it is possible to use a mass flowmeter on a wide variety of process fluids without need for recalibration or compensation to specific fluid parameters. | Mass flowmeters can be used for the following applications: Clean liquids Dirty liquids Slurries Gases Steam Liquids with entrained gases |
The Coriolis principle flowmeter is a true mass flowmeter because it uses the
properties of mass to measure mass. It is relatively easy to apply and size. Because
it possesses no moving parts, it exhibits low maintenance requirements and does
not require frequent calibration. Wetted parts that can be constructed of a variety
of materials make it adaptable to many corrosive fluids as well as fluids containing
solid or fibrous particles. Coriolis flowmeters can also measure the density of
the process fluid, making it possible to infer volume and/or the flow of one component
in a two-component flow stream (e.g., dry solids flow rate of a slurry).
Coriolis flow sensors can be designed for intrinsically safe operation in hazardous
locations. The electronic transmitters can be packaged in explosion-proof housings.
Principles of Operation
Mass Flow
Coriolis principle mass flowmeters are manufactured in a variety of shapes,
sizes, and materials of construction. All of these factors influence the sensitivity
of the meter to flow rate; however, the basic principle of operation remains the
same. Simply stated, Coriolis meters operate on the basic principles of motion
mechanics. The fluid in motion through a vibrating flow tube is forced to take on a
transverse acceleration as it moves toward the point of peak amplitude of vibration.
Conversely, the fluid decelerates as it moves away from the point of peak
amplitude as it exits the tube. The moving fluid exerts a force on the inlet side of
the tube in resistance to this acceleration, causing this side of the tube to lag
behind its no-flow position. On the outlet side, the force exerted by the flowing
fluid is in the opposite direction as the fluid resists the deceleration. This force
causes the outlet side of the tube to lead ahead of its no-flow position. The result
of these forces is a twisting reaction of the flow tube during flow conditions as it
traverses each vibrational cycle. This is demonstrated with a U-shaped tube in
Figure 12-1. Fluid at point B moves up and down faster than fluid at A or C.
