Standard orifice meter

Meter for Measuring Air (or Gas) Volume. A standard orifice meter is generally used to measure air (or gas) injection volume rates. 

Stagewise mass transfer processes 622 Standard orifice meter 249... 

AGA. Manual of Petroleum Measurement Standards. Chapter 14—Natural Gas Fluids Measurement, Section 3 Orifice Metering of Natural Gas and Other Related Hydrocarbon Fluids. AGA Report No. 3. (ANSI/API 2530, 1985 and CPA 8185, 1985). American Gas Association, Cleveland, Ohio. 

Air Flow Typical gas flow rates for an orifice scrubber unit are 0.47 to 24 standard cubic meters per second (sm /sec) (1,000 to 50,000 standard cubic feet per minute (scfm)). 

Pollutant Loading Orifice scrubbers can accept waste flows with PM loadings up to 23 grams per standard cubic meter (g/sm ) or 10 grains per standard cubic foot (gr/scf), or higher, depending upon the nature of the PM being controlled. 

The orifice plate is simple to manufacture and has a relatively low cost. It does, however, create a quite large permanent pressure loss when installed in the ductwork. The venturi is smoothly shaped with a low permanent pressure loss but requires more space and is more expensive. The nozzle is a compromise betw een the orifice and the venturi. All three devices are standardized flow meters with very detailed descriptions of their geometry, material, manufacturing, installation, and use. -... 

The coefficients for venturi meters, flow nozzles, and orifice meters vary with Reynolds number as shown in Figs. 10.7 to 10.10. The curve for an orifice meter shown in Fig. 10.10 covers an unusually wide range of both viscosity and Reynolds number. The fluids used were water and a series of oils up to a very viscous road oil, and for each fluid a number of different velocities were used, so that the curve represents points for many combinations of velocity and viscosity. Although the orifice plate may not be a standard beveled form, the value of C for high Reynolds numbers agrees closely with the value of C in Fig. 10.10 for a diameter ratio of 0.75. 

Extensive and detailed design standards for orifice meters are available in the literature. They must be followed if the performance of a meter is to be predicted accurately without calibration. For approximate or preliminary design, however, it is satisfactory to use an equation similar to Eq. (8.34) as follows ... 

The pitot-static tube is the standard device for measuring the airspeed of airplanes and is often used for measuring the local velocity in pipes or ducts, particularly in air pollution sampling procedures. One can easily identify the pitot-static probes projecting from the front of modern commercial airplanes look next time you are at an airport. For measuring flow in enclosed ducts or channels the venturi meter and orifice meters discussed below are more convenient and more frequently used. 

Figure 5.12 is based on a standard location of the upstream and downstream pressure taps. When the taps are in some other location, the value of is different [2]. In comparison with venturi meters, orifice meters have high pressure losses— high — and correspondingly high pumping costs, but because they are mechanically simple, they are cheap and easy to install. For small-size lines, orifice meters are much more common than venturi meters. 

ISO 5167, the International Standard on orifice metering, has been with us now for about 5 years. 

From oirr industry standpoint, the first two of these help. They don t really improve the level of pieeision available, but they do provide a sound foundation for future ehange. The ISO and ASME Standards tend to add confusion in this area, but on the bright side, underseore the importance of a eonsistent teehnieal approach to large volume measurement These particular methods provide two alternate means of evaluating orifice meters. The answers are different but in most cases within the preeision mentioned earher. The key point, is they do not provide any improvement in that precision. 

The second method of measuring energy flow using independent measurements of volumetric flow was provided by a Lone Star Gas orifice meter. Input to the Elliot flow computer included the pressure differential across the orifice plate and the pressure and temperature of the gas at the orifice. A conunercial GB-2000 instrument from Precision Measurement Incorporated provided a continuous input of specific gravity to the flow computer. Calorific value also was provided by the GB-2000. The flow computer used these inputs to calculate the volumetric flow at standard conditions. It then corrected for... 

Other secondary standards, including the venturi meter, orifice meter and manometer have less accuracy than those previously discussed and therefore, are not often used by industrial hygienists for pump calibration. 

By standard instrumentation is meant the standard equipment used for single-phase flow studies—manometers, orifice meters, venturis, etc. The manometer principle for measuring pressure drops is a very viable technique in gas-solid flow. Calibration of the... 

Fhw measurement. Orifice. Flow of liquid-metal fuels, much like flows of water or other li( uids, is most commonly measured wnth standard orifices [22,25,30]. Work done at the Engineering Research Center, I niversity of California [30,50] has demonstrated that an orifice may be calilu atcd with water, and the calibration may then be used directly for hea y metal (Bi or Fb-Bi) Aoav metering. The error introduced in this manner is only between 3 and 5%. 

Accuracy Square-edged orifices and venturi tubes have been so extensively studied and standardized that reproducibihties within 1 to 2 percent can be expected between standard meters when new and clean. This is therefore the order of reliabihty to be had, if one assumes (1) accurate measurement of meter differenfial, (2) selection of the coefficient of discharge from recommended published literature, (3) accurate knowledge of fluid density, (4) accurate measurement of critical meter dimensions, (5) smooth upstream face of orifice, and (6) proper location of the meter with respect to other flow-disturbing elements in the system. Care must also be taken to avoid even sh t corrosion or fouliug during use. 

International Organization for Standards Report DIS 5167, Geneva, 1976). Similar equations are given for other kinds of orifice taps and for nozzles and Venturi meters. 

C. Flow Measurement by Pressure Drop across an Orifice. Another common scheme for the measurement of flow is based on the determination of the pressure drop on either side of a constriction, such as an orifice or venturi. Either a liquid-filled differential manometer or a pressure transducer with associated digital readout may be used for this pressure measurement. The flow rates determined by these meters are in units such as cm3/s, and it is necessary to make a correction for total pressure to convert these to standard cm3/s or mol/s. 

Bean, H. S., Buckingham, E., and Murphy, P. S., Discharge Coefficients of Square-Edged Orifices for Measuring the Flow of Air, U.S. National Bureau of Standards Research Paper 49, ASME Fluid Meters Report, 1931. 

Dirt and moisture are the worst enemies of the performance of all PD gas meters, so inlet filtering should be used when indicated. Pressure and temperature should either be controlled or compensated. The testing (or proving, as it is called in the gas utility industry) of gas meters is usually done by an accurately calibrated "bell" of cylindrical shape that is sealed in a tank by a suitable liquid. The lowering of the bell discharges a known volume of air through the meter under test. Other standards used to calibrate gas meters are calibrated orifices and critical flow nozzles. These devices compare rates of flow rather than fixed volumes. 

Orifice Plate Meter. Figure 9 illustrates an orifice plate meter. Here fluid is suddenly accelerated as it passes through an orifice in a plate, which is normally held between two flanges. Pressure is measured upstream (point 1) and downstream (point 2) of the orifice. There are a number of standard positions for the pressure tapings, D 79/2 ,... 

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