Turbine flow measurement

Water flow measure- Turbine flow meters Magnetic P... 

Mechanical flow measurement Turbine flow meter di-electric... 

The principal classes of flow-measuring instruments used in the process industries are variable-head, variaBle-area, positive-displacement, and turbine instruments, mass flowmeters, vortex-shedding and iiltrasonic flowmeters, magnetic flowmeters, and more recently, Coriohs mass flowmeters. Head meters are covered in more detail in Sec. 5. 

When testing to estabhsh the thermodynamic performance of a steam turbine, the ASME Performance Test Code 6 should be followed as closely as possible. The effec t of deviations from code procedure should be carefully evaluated. The flow measurement is particularly critical, and Performance Test Code 19 gives details of flow nozzles and orifices. The test requirements should be carefully studied when the piping is designed to ensure that a meaningful test can be conducted. 

Flow Rate. The values for volumetric or mass flow rate measurement are often determined by measuring pressure difference across an orifice, nozzle, or venturi tube. Other flow measurement techniques include positive displacement meters, turbine flowmeters, and airflow-measuring hoods. 

There are many other flow measurement devices including Onlicc/Venturi meters, turbine meters, and more sophisticated instruments using ultrasonic, magnetic, and Coriolis effect techniques. Orifice/Venturi type meters have a restriction causing a pressure drop related to the flow rate of liquid. Such meters are popular because of their low cost however, their accuracy can be compromised by upstream elbows and valves. Turbine meters are designed so that rotation speed varies linearly with the... 

This chapter discusses the unit operations of flow measurements and flow and quality equalizations. Flow meters discussed include rectangular weirs, triangular weirs, trapezoidal weirs, venturi meters, and one of the critical-flow flumes, the Parshall flume. Miscellaneous flow meters including the magnetic flow meter, turbine flow meter, nutating disk meter, and the rotameter are also discussed. These meters are classified as miscellaneous, because they will not be neated analytically but simply described. In addition, liquid level recorders are also briefly discussed. 

Flow rate is typically measured in gallons per minute (gpm) or gallons per hour (gph). A variety of devices can be used to accomplish flow measurement. Common examples of flow measurement devices are orifice plates, venturi nozzles, nutating disc meters, turbine flow meters, oval gear meters, rotameters, pitot tubes, weir and flume, and flow transmitters. Figure 7-4 shows a few examples of flow-measurement devices. 

Some flow calorimeters (continuous calorimeters) make use of air as a heat transfer medium in other cases, gases or liquids react with each other or are products of the reaction. In the latter case, a possible approach to the measurement of amounts of substances consists in allowing the newly formed phase (usually a gas) to leave the system via a flow meter. Here the flow rate provides a measure of the quantity of substance transformed per unit time. Usually a pressure difference is the measurand as in capillary flow meters or is caused by the back pressure of the measuring instrument however, the possibility of pressure rises (caused by a buildup ) in the vessel must be taken into account. Other techniques for measuring amounts of gas make use of displacement gas meters, turbine meters, or ultrasonic meters. In these cases, the volume flow is the measured quantity. For measuring the mass flow, Coriolis or thermal mass flow meters can be used. In any case, it is very difficult to reduce the uncertainty of flow measurements below approximately 1%. This can only be achieved in exceptional cases when great effort is made to calibrate the meter with fluids of similar and known thermophysical properties (e.g., heat capacity, thermal conductivity, viscosity, density, etc.). 

Rotameter Ultrasonic type Turbine flow meter Electromagnetic flow meter Good for upstream flow measurements Used in conjunction with variable inductance sensor Good for very high flow rates Can be used for both upstream and downstream flow measurements Not suited for fluids containing abrasive particles Relationship between flow rate and angular velocity is linear Least intrusive as it is noncontact type Can be used with fluids that are corrosive, contaminated, etc. The fluid has to be electrically conductive... 

Flow measurement flow meters using ultrasonics, electromagnetics, turbines, and pressure differential measurement. 

This control Is Illustrated in Fig. 4 it Is based on a signal representing demanded feed rate which is derived, from a combination of steam flow to the turbine and drum level error. This demanded feed rate is then met by a conventional three-term controller operating on the feed valve and using flow measurement in the feed pipe. 

The turbine-type flow meter probably has been used for flow measurement of liquefied gases more than any other type of meter. These meters have all of the disadvantages of the variable-area meters, are more expensive, have moving parts, and require electronic circuitry. There is a tendency to trust the reading of a turbine meter more than an orifice even though neither meter has been calibrated with the fluid being measured. 

The last components of a system are those required to monitor operating conditions and record test data. In the Bell circuit, a sharp-edged orifice is used as the principal flow-measuring device. One unitwas in service for over a year, and at the end of that time the calibration was reproduced within Vjo, The orifice plate was made of monel and showed no evidence of attack or of rounding of the sharp edges. Several other agencies have recently reported success with turbine-type flow meters constructed specifically for liquid-fluorine service. 

The turbine-type flowmeter is a popular instrument for measuring cryogenic fluid flow. It has had extensive cryogenic experience from which design improvements have resulted. To infer mass flow, attempts have been made to couple the meter s flow measurement with fluid temperature and fluid pressure measurements. Then, by computation, an inference of mass flow is made. This inferred mass flow has not been highly accurate. This is understandable when one considers that three separate measurements, with their attendant inaccuracies, are combined in a computation, which is then referred to fluid p-V-T data. 

As a true volume flow measurement technique, the turbine flowmeter is an outstanding device having excellent repeatability. To achieve this excellence, it must, however, be used correctly. All too frequently, the turbine flowmeter is misapplied either by using it outside of its specified flow range or in two-phase fluid applications. 

MFC-4M-1986(R1997) Measurement of Gas Flow Iq Turbine Meters Order No. K00118 29.00... 

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