Vortex meters

When a bluff body is interspersed in a fluid stream, the flow is split into two parts. The boundary layer (see Chapter 11) which forms over the surface of the obstruction develops instabilities and vortices are formed and then shed successively from alternate sides of the body, giving rise to what is known as a von Karman vortex street. This process sets up regular pressure variations downstream from the obstruction whose frequency is proportional to the fluid velocity, as shown by Strouai. 9. Vortex flowmeters are very versatile and can be used with almost any fluid — gases, liquids and multi-phase fluids. The operation of the vortex meter, illustrated in Figure 6.27, is described in more detail in Volume 3, by Gjnesi(8) and in a publication by a commercial manufacturer, Endress and Hauser.10 ... 

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,... 

Velocity Meters Velocity meters measure fluid velocity. Examples include electromagnetic, propeller, turbine, ultrasonic Doppler, ultrasonic transit time, and vortex meters. Section 8 describes the principles of operation of electromagnetic, turbine, ultrasonic, and vortex flowmeters. 

Vortex meters are being employed increasingly because of their accuracy, range, precision and relative insensitivity to fluid properties. They can be used for gases, saturated and superheated steam, low viscosity clean and dirty liquids, and cryogenic fluids 6 . They are not recommended for use when Re < 104. 

While fishing in Transylvania, Theodore von Karman noticed that downstream of the rocks the distance between the shed vortices was constant, regardless of flow velocity (Figure 3.104). From that observation evolved the three types of vortex meters the vortex shedding, the vortex precession, and the fluidic oscillation (Coanda) versions. All three types detect fluid oscillation. They have no moving components and can measure the flow of gas, steam, or liquid. 

A Flow Element (FE206 and PDT206) is recommended to provide a measure of the fuel gas flow rate to the burner. Flow elements may include orifice plates (stainless steel is recommended) annubars vortex meters mass flow meters and others, provided that all of the materials are fuel gas compatible and dimensional requirements are satisfied. 

Quite a number of technologies are available for measuring volumetric flow rates. These include differential pressure transmitters, vortex meters and magnetic flow meters. Each has its advantages and disadvantages. 

Orifice meters, turbine meters, rotary displacement meters, vortex meters and high-pressure diaphragm meters are used for volume measurement at flowing conditions. The different volnme measurement systems are selected according to throughput, measuring range and offtake pattern (ref. 2). 

Vortex meters are intrusive because they rely on disturbing the flow regime by placing an object in the fluid stream to produce an oscillatory motion downstream. The object can take many shapes but often a thin wire is used, as shown in Figme 6.11, which minimizes the pressure drop. The oscillatory motion is referred to as a vortex and may be detected by piezoelectric transducers, or magnetic or optical sensors. The number of vortices present is proportional to the volumetric flow rate. 

Feed tank for metering pump placed at a height—it can feed in liquid even when pump is stopped. This is not advisable. This tank shall be at a lower level. Either strainers not provided at all or there are bigger holes in strainer screen in inlet line of metering pumps or instrumentation probe (concentration analyser). Sufficient straight lengths (as recommended by manufacmrers) not provided before and after flowmeters like orifice meters/vortex meters. 

The three valves are all built for chlorine service. Vortex meters upstream of the control valves measure and integrate the various flows. Integration of the flow to the scrubber is the least important, but given the measurement of the flow rate, it is of little added cost. A separate meter located before division of the flow can measure the total flow, or the output of the three individual meters can be added together. The valve positioners may be calibrated for ranges of 15-20 mA (direct user), 9-15 mA (liquefiers), and 4-9 mA (scrubber). The two process valves should have linear characteristics. They should be sized for fiill plant output when 90% open. Normally allowed pressure drops are 5-15 kPa for the direct-use valve and 20-30kPa for the liquefier valve. The scrubber... 

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