Flowmeters types

General Principles There are two main types of mass flowmeters (1) the so-called true mass flowmeter, which responds directly to mass flow rate, and (2) the inferential mass flowmeter, which commonly measures volume flow rate aud flmd density separately. A variety of types of true mass flowmeters have been developed, including the following (a) the Maguus-effect mass flowmeter, (b) the axial-flow, transverse-momentum mass flowmeter, (c) the radial-flow, transverse-momentum mass flowmeter, (d) the gyroscopic transverse-momentum mass flowmeter, aud (e) the thermal mass flowmeter. Type b is the basis for several commercial mass flowmeters, one version of which is briefly described here. 

Flowmeters can be classified as either positive displacement or turbine type meters. Listed below is a brief description of each flowmeter type ... 

Flowmeter Type Permanent Pressure Loss (in velocity heads)... 

A batch microcalorimetric experiment, very similar to the one just described, is possible with a diathermal heat flowmeter type of microcalorimeter, which is less versatile than the Tian-Calvet microcalorimeter (especially in its temperature range and ultimate sensitivity), but of a simpler design. In the Montcal microcalorimeter (Partyka et al., 1989), the thermopile with up to 1000 thermocouples is replaced by a few thermistors. 

Linearizing the output of the transmitter. Functions such as square root extraction of the differential pressure for a head-type flowmeter can be done within the instrument instead of within the control system. 

Axial-Flow Transverse-Momentum Mass Flowmeter This type is also referred to as an augiilar-momeutum mass flowmeter. One embodiment of its principle involves the use of axial flow through a driven impeller aud a turbine in series. The impeller imparts augiilar momentum to the fluid, which in turn causes a torque to be imparted... 

Inferential Mass Flowmeter There are several types in this category, including the following ... 

Goldberg and Boothroyd [Br Chem. Eng., 14, 1705-1708 (1969)] describe several types of solids-in-gas flowmeters and give an extensive bibhography. 

Flow measurements using nonintrusive or low mechanical ac tion principles are desired, such as magnetic, vortex-shedding, or Coriolis-type flowmeters. Orifice plates are easy to use and reliable but have a limited range and may not be suitable for streams which are not totally clean. Rotameters with glass tubes should not be used. 

Before taking the sample train to the test site, it is wise to prepare the operating curves for the particular job. With most factory-assembled trains, these curves are a part of the package. If a sampling train is assembled from components, the curves must be developed. The type of curves will vary from source to source and from train to train. Examples of useful operating curves include (1) velocity versus velocity pressure at various temperatures (6), (2) probe tip velocity versus flowmeter readings at various temperatures, and (3) flowmeter calibration curves of flow versus pressure drop. It is much easier to take an operaHng point from a previously prepared curve than to take out a calculator and pad to make the calculahons at the... 

Dali Flow Tube - The advantage is this type of flowmeter is that it has a permanent head loss of only 5 % of the measured pressure differential. This is the lowest pressure drop of all orifice meter designs. Flow ratios as high as 1 10 (e.g., 1.0 to 10 kg/s) can be measured within + 2% of actual flow. Dali flow mbes are available in different materials and diameters up to 1500 mm. 

Other types of flowmeters that are applicable to flare gas metering include... 

Whichever, the retained design (type a, b, or c), there are always different options to control the outlet flowrates. A pump, analog valve, and flowmeter or pressure... 

Vortex-induced separator, 22 62-63 Vortex-induced vibration, 11 756 Vortex meters, mass flowmeters, 20 681 Vortex patterns, 11 755 Vortex precession meters, 11 668 Vortex shedding, 11 756 Vortex shedding meters, 11 668-669 Vortices, superconductor, 23 824-825 Voyage charters, 25 327 VP Sandoflam 5085, 11 491 V-type inks, 14 326 Vulcanizable silicone rubber, 25 129 Vulcanizable silicones, properties and applications of, 22 594-595, 596-597 Vulcanizates EPDM, 10 713 EPM/EPDM, 10 715 ethylene-acrylic elastomer, 10 698,... 

A detailed description of the various methods of measuring solids flowrates has been given by Liptak(17) and Table 1.2, taken from this work, gives a summary of the principal types of solids flowmeters in common use. 

For steady-state, isothermal, single-phase, uniform, fully developed newtonian flow in straight pipes, the velocity is greatest at the center of the channel and symmetric about the axis of the pipe. Of those flowmeters that are dependent on the velocity profile, they are usually calibrated for this type of flow. Thus any disturbances in flow conditions can affect flowmeter readings. 

In the process industries, flow measurement devices are the largest market in the process instrumentation field. Two web sites for process equipment and instrumentation, www.globalspec.com, and www.thomasnet.com, both list more than 800 companies that offer flow measurement products. There are more than one hundred types of flowmeters commercially available. The aforementioned web sites not only facilitate selection and specification of commercial flowmeters, but also provide electronic access to manufacturers technical literature. 

According to Head [Trans. Am. Soc. Mech. Eng., 78, 1471-1479 (1956)], a pulsation-intensity limit of F = 0.1 is recommended as a practical pulsation threshold below which the performance of all types of flowmeters will differ negligibly from steady-flow performance (an error of less than 1 percent in flow due to pulsation). F is the peak-to-trough flow variation expressed as a fraction of the average flow rate. According to the ASME Research Committee on Fluid Meters Report (op. cit., pp. 34—35), the fractional metering error E for liquid flow i he "... 

Coriolis Mass Flowmeter This type, described in Sec. 8, offers simultaneous direct measurement of both mass flow rate and fluid density. The Coriolis flowmeter is insensitive to upstream and downstream flow disturbances, but its performance is adversely affected by the presence of even a few percent of a gas when measuring a liquid flow. 

Let us say we have an ordinary orifice-type flowmeter, as shown in Fig. 21.5 (see Chap. 6, How Instruments Work ). What happens if the low pressure (i.e., the downstream) orifice tap plugs Does the indicated flow go up or down ... 

Flowmeter. To monitor flow of carrier gas, a variety of devices are available, such as differential capillary, thermal conductivity, ionization, rotameters, and calibrated soap-film tubes Measurement of the flow may either be continuous or intermittent, and the flowmeter may be placed either in front of the column or at the carrier gas outlet. The soap-film type is most commonly used because of its economy and ease of operation. 

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