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	Application and Selection of flow In this section, an overview is given of the availability and characteristics of some of the most widely used flow sensors. In addition, emphasis is given to the latest developments, such as the polyphase (oil/water/gas) and the wide-rangeability dual-rotor turbine flowmeters. General guidelines are provided about selecting the best flow sensor for a particular application	0 Posts 0 Topics
	BTU Flowmeters for Gaseous Fuels The heat flow rate provided by the burning of a fuel gas can be measured by detecting its mass flow rate and multiplying it by its heating value, which can be detected by wobble index sensors or calorimeter	0 Posts 0 Topics
	Anemometers Anemometers are used to measure air and gas flows in a variety of applications, including such tasks as the balancing of HVAC systems using hand-held air velocity meters. They are also used in stacks to measure the velocity of wet and dirty gases and in wind detection applications to obtain threedimensional wind velocity profiles using Doppler-type sensors. Anemometer designs include pitot, mechanical (vane, cup, propeller, turbine), thermal, and Doppler types. Pitot tubes and thermal flowmeters are discussed later in this chapter. This section concentrates on the mechanical and Dopplertype anemometers	0 Posts 0 Topics
	BTU Flowmeters for Heat Exchangers BTU flowmeters play a critical role in monitoring the energy flows and increasing energy efficiency in industry. The first step toward an energy-efficient plant design is a reliable energy audit throughout the plant. Such overall heat balance around the plant can be prepared only if the individual loads are accurately and separately measured	0 Posts 0 Topics
	Cross-Correlation Flow Metering Several of the above process variables (such as temperature, 4,5 gamma radiation, and capacitive density 6 ) have been investigated as potential sensors for correlation flowmeters. One instrument has been developed that uses the principle of ultrasonic cross-correlation to measure heavywater flow	0 Posts 0 Topics
	Elbow Taps Flow measurement using elbow taps depends on the detection of the differential pressure developed by centrifugal force as the direction of fluid flow changes in a pipe elbow. Taps are located on the inner and outer radii in the plane of the elbow. The pressure taps are located at either 45 ° or 22.5 ° from the inlet face of the elbow	0 Posts 0 Topics
	Flow Switches Flow switches are used to determine if the flow rate is above or below a certain value. This value (the setpoint) can be fixed or adjustable. When the setpoint is reached, the response can be the actuation of an electric or pneumatic circuit	0 Posts 0 Topics
	Jet Deflection Flow Detectors Volumetric flow rate in a pipe or duct can be inferred from a measurement of gas velocity, and one of the methods to measure this velocity is jet deflection detection	0 Posts 0 Topics
	Laminar Flowmeters Laminar flowmeters are intended for very low flow rates where other types of meters are either marginal in performance or cannot be used at all. Laminar flowmeters can be constructed by various methods, but the most common is with capillary tubes	0 Posts 0 Topics
	Magnetic Flowmeters In recent decades, there has been a great deal of interest in Coriolis mass flowmeters (CMFs). The market for CMFs grew dramatically in the late 1980s and the 1990s. Today, CMFs are widely accepted in many industrial fields, and their performance has improved steadily	0 Posts 0 Topics
	Mass Flowmeters—Miscellaneous In this section, some of the other mass flow detection methods are covered RADIATION-TYPE MASS FLOWMETERS ,ANGULAR MOMENTUM-TYPE MASS FLOWMETERS One of the earliest methods of mass flow determination was to install two separate sensors—one to measure the volumetric flow and the other to detect the density of the flowing stream—and then to use the two transmitter signals as inputs into a mass flow computing module .The principle of angular momentum can best be described by referring to Newton’s second law of angular motion and the definition of angular momentum	0 Posts 0 Topics
	Mass Flowmeters—Thermal Thermal flowmeters can be divided into the following two categories: 1. Flowmeters that measure the rise in temperature of the fluid after a known amount of heat has been added to it. They can be called heat transfer flowmeters. 2. Flowmeters that measure the effect of the flowing fluid on a hot body. These instruments are sometimes called hot-wire probes or heated-thermopile flowmeters . Both types of flowmeters can be used to measure flow rates in terms of mass, which is a very desirable measurement, especially on gas service	0 Posts 0 Topics
	Metering Pumps A metering pump is a positive-displacement pump providing a predictable and accurate rate of process fluid flow. Normally, the application design, specification, and use of pumps are the concern of mechanical engineers and machinery designers. Metering pumps, however, are sometimes used to actually measure or control flow rate, and in many cases they are the final control elements in an instrumentation loop. Therefore, the instrument engineer should be familiar with their operation and application.	0 Posts 0 Topics
	Orifices Head-type flowmeters compose a class of devices for fluid flow measurement including orifice plates, venturi tubes, weirs, flumes, and many others. They change the velocity or direction of the flow, creating a measurable differential pressure or “pressure head” in the fluid.	0 Posts 0 Topics
	Pitot Tubes and Area Averaging Units For the measurement of the velocities of fluids, in 1732, Henri de Pitot invented the pitot tube. Pitot tubes detect the flowing velocity at a single point (standard), at several points that lead into an averaging probe (multiported), or at many points across the cross section of a pipe or duct (area-averaging). Their advantages are low cost, low permanent pressure loss, and the capability of inserting the probe-type sensors into the process pipes while the system is under pressure (wet- or hot-tapping). The disadvantages of pitot tube-type sensors are low accuracy, low rangeability, and the limitation of being suitable only for clean liquid, gas, or vapor service unless purged	0 Posts 0 Topics
	Polyphase (Oil/Water/Gas) Flowmeters Whereas most flow measurements are carefully designed to operate in single phase (gas, vapor, liquid), there are many circumstances in which the ability to distinguish the components of a liquid/vapor/gas mixture (or, indeed, multiple immiscible liquids, vapor, and gas) in the presence of solids is highly desirable.	0 Posts 0 Topics
	Positive-Displacement Gas Flowmeters Positive-displacement gas meters measure by internally passing isolated volumes of gas that successively fill and empty compartments with a fixed quantity of gas. The filling-andemptying process is controlled by suitable valving and is translated into rotary motion to operate a calibrated register or index that indicates the total volume of gas passed through the meter.	0 Posts 0 Topics
	Positive-Displacement Liquid Meters and Provers Positive-displacement meters split the flow of liquids into separate known volumes, the size of which are based on the physical dimensions of the meter. The meters act as counters or totalizers of the number of these volumes as they pass through. These mechanical meters have one or more moving parts in contact with the flow stream and physically separate the fluid into increments	0 Posts 0 Topics
	Purge Flow Regulators Purge flows are low flow rates of either gases or liquids. They serve to protect pressure taps from plugging or being contacted by hot or corrosive process fluids. Inert gas purging can also serve to protect electrical devices from becoming ignition sources by maintaining a positive pressure of incombustible gases inside their housings. In the case of analyzers, purging protects the cleanliness of the optics	0 Posts 0 Topics
	Segmental Wedge Flowmeter The shape of the flow opening of a segmental wedge flowmeter is similar to that of a segmental orifice except that the obstruction to flow is less abrupt (more gradual). Also, the sloping entrance somewhat resembles the shape of the various flow tubes	0 Posts 0 Topics
	Sight Flow Indicators Sight flow indicators (SFIs, a.k.a. flow glasses) provide a window into a pipe when visual inspection of a process fluid is necessary .The plain design is used to observe physical characteristics of the process fluid; it is not meant to provide full pipe flow indication. Four types of indicating devices are incorporated when flow indication is desired	0 Posts 0 Topics
	Solids Flowmeters and Feeders Many types of solids flowmeters are currently available. The majority depend on some method of weighing, but others utilize a variety of other phenomena ranging from various forms of radiation to impact force determination, and from dependence on electrical properties to centrifugal force	0 Posts 0 Topics
	Target Meters Material buildup in front of orifice plates can cause both measurement errors and plugging when the process stream is a liquid slurry or a gas carrying wet solids. The annular orifice and the target flowmeter were introduced to solve this problem by providing an annular opening for the solids to pass through	0 Posts 0 Topics
	Turbine and Other Rotary Element Flowmeters Turbine meters are available for liquid, gas, and very low flow rates in both full-bore and insertion designs. The most widely used type is the full-bore meter for liquid service	0 Posts 0 Topics
	Ultrasonic Flowmeters The image of ultrasonic flowmeters was rather tarnished for decades because the complexity of the measurement produced was not initially realized. Factors that affect the measurement include the influence of the pipe, the flow profile, and the many practical obstacles and environment interferences that can occur	0 Posts 0 Topics
	Variable-Area, Gap, and Vane Flowmeters The variable-area flowmeter is also a head-type flow sensor, but it does not measure the pressure drop across a fixed orifice; instead, the pressure drop is held relatively constant, and the orifice area is varied to match the flow	0 Posts 0 Topics
	V-Cone Flowmeter In a venturi-cone (V-cone) meter, a cone is positioned in the center of a metering tube .This cone reduces the cross-sectional area available for the process flow and, much like an orifice restriction, generates a lowpressure region downstream of the flow element. The square root of the difference between the low pressure downstream and the upstream pressure is related to the flow through the meter.	0 Posts 0 Topics
	Vortex and Fluidic Flowmeters This section is devoted mainly to the vortex-shedding flowmeter and its variations, including the earlier designs of vortexprecession (swirl) meters and the recent combination designs of vortex bypass elements around orifices. Included in this category of devices are oscillating fluidic flowmeters using the Coanda effect	0 Posts 0 Topics
	Weirs and Flumes Weirs are apertures in the top of a dam, across a channel through which flows the liquid to be measured .The aperture may be rectangular, trapezoidal , or V-notch . The special case of a trapezoidal weir with side slopes of 1:4 is known as a Cippoletti weir ; this form leads to a simplified flow calculation. V-notch weirs generally have a notch angle from 30 to 90 , depending on required flow capacity	0 Posts 0 Topics
	Venturi Tubes, Flow Tubes,and Flow Nozzles Venturi tubes, flow nozzles, and flow tubes, like all differential pressure producers, are based on Bernoulli’s theorem. General performance and calculations are similar to those for orifice plates	0 Posts 0 Topics

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