Rotameter, example

The flow of the various feeds to the extraction system may be by gravity from elevated feed vessels via, for example, rotameter type flowmeters. It is now becoming common practice to feed from tanks at a similar level to the extractors, via metering pumps. The accuracy required depends upon the... 

Rotameters The rotameter, an example of which is shown in Fig. 10-21, has become one of the most popular flowmeters in the chemical-process industries. It consists essentially of a plummet, or float, which is free to move up or down in a vertical, slightly tapered tube having its small end down. The fluid enters the lower end of the tube and causes the float to rise until the annular area between the float and the wall of the tube is such that the pressure drop across this constriction is just sufficient to support the float. Typically, the tapered tube is of glass and carries etched upon it a nearly linear scale on which the position of the float may be visually noted as an indication of the flow. 

Rate Meter Measures the instantaneous volume flow rate through the sampling systems. An example would be a rotameter or venturi meter. Used to set precise flow rate for flow sensitive sampling devices. 

Thus, sizing rotameters requires using either Equation 8.26 or Equation 8.28 to calculate the flow rate of the standard fluid. Then use Table 8.3, supplied by a manufacturer, to select a rotameter. The procedure for sizing a rotameter is illustrated in Example 8.3. 

Pumps should be cahbrated with a rotameter [27] prior to and after sampling. Analytical instruments must also be calibrated before measurements. For example, GC/MS must be cahbrated for mass and retention times using reference standard materials [70] and comparison made with the fragmentation patterns of known standards, usually a deuturated compound like toluene-dg. Similarly, the method detection limit must be determined by finding the standard deviation of seven replicate analyses and multiplying it by the f-test value for 99% confidence of seven values [30,62]. It is also usual for internal standards to be added to the samples and to evaluate the correlation coefficients of each standard used when multilevel calibration is employed. For automatic thermal desorption tubes, external and internal standardisations are achieved by injecting solutions of standards into the tubes [27,28] for canisters, solutions of standards are injected into the canisters followed by zero air. 

Example 5.10. Our rotameter has been calibrated for nitrogen at room temperature and atmospheric pressure the calibration shows that for a reading (float position) of 50 percent of the height of the rotameter tube, the volumetric flow rate is 100 cm /min. We now need to measure the flow of... 

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. 

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