Bubble meter method

Calibrate personal sampling pumps before and after each day of sampling, using either the electronic bubble meter method or the precision rotameter method (that has been calibrated against a bubble meter). 

The electronic bubble meter method consists of the following ... 

Flowmeters.— The measurement of gas-flow rate is usually carried out with a soap-bubble meter although other methods involving rotameters and capillary manometers are available. The soap-bubble meter is an inexpensive, easy to operate, direct method which has good accuracy. 

Flow meters on field sampling instruments are calibrated using one of several methods. Primary standards are tliose which measure volume directly and are, therefore, preferred. Primary air flow standards include bubble meters, spirometers and Mariotti botdes. The time required to draw a measured volume of air through these systems is measured and the resulting flow rate is calculated. These methods are typically accurate to within one percent. 

Assemble the polystyrene cassette filter holder using the appropriate filter for the sampling method. If a cassette adapter is used, care should be taken to ensure that it does not come in contact with the back-up pad. When calibrating with a bubble meter, the use of cassette adapters can cause moderate to severe pressure drop in the sampling train, which will affect the calibration result. If adapters arc used for sampling, then they should be used when calibrating. 

Doppler Flow Meters. Doppler flow meters sense the shift in apparent frequency of an ultrasonic beam as it is reflected from air bubbles or other acoustically reflective particles that ate moving in a Hquid flow. It is essential for operation that at least some particles ate present, but the concentration can be low and the particles as small as ca 40 p.m. CaUbration tends to be influenced by particle concentration because higher concentrations result in mote reflections taking place neat the wall, in the low velocity portion of the flow profile. One method used to minimize this effect is to have separate transmitting and receiving transducers focused to receive reflections from an intercept zone neat the center of the pipe. 

The Doppler meter may be used wherever small particulate solids, bubbles or droplets are dispersed in the fluid and are moving at essentially the same velocity as the fluid stream which is to be metered. A continuous ultrasonic wave is transmitted, again at an acute angle to the wall of the duct, and the shift in frequency between the transmitted and scattered waves is measured. This method of measurement of flowrate is frequently used for slurries and dispersions which present considerable difficulties when other methods are used. 

Different methods used for calibrating samplers include rotometers, wet-test meters, pressure gauges across fixed orifices, mass flow meters, hot wire flow meters and bubble tubes. Each of these calibration devices requires an appropriate correction factor. Some of the devices measure mass flow rather than volumetric flow. Sampling requires volumetric flow calibration. 

Tests for Thermal Stability. HCl Evolution. In a modification of ASTM Method D793-49 (1965), utilizing the apparatus described therein, 5 grams of polymer were heated at 180°C in a flask immersed in an oil bath, and preheated nitrogen was passed over the sample. Under these conditions the sample slowly evolved hydrogen chloride which was carried by the nitrogen and bubbled into 70 ml of distilled water. The pH of the solution was measured continuously with a pH meter and con-... 

Second, a peak-intensity ultrasound echo can be used to detect the gas-liquid interface, but in this case the aim is the development of a flow meter capable of estimating the ratio of component phases accurately and in real time. Our results are promising for the estimation of the liquid flow rate of gas-liquid two-phase flow further research will produce valuable data that will allow the estimation of flow rates for the two phases simultaneously. The results presented here show the liquid flow rate estimated by the peak echo intensity method can provide an accurate estimate of the actual liquid flow rate. This method can be applied to pure liquid as well as to a two-phase flow where the void fraction is as high as 50%. The flows tested are of the stratified, elongated bubble, and slug flow types. Other types of flow such as wave flow and dispersive flow were not tested the present experimental setup does not provide the gas and liquid flow rates needed to achieve such flows. 

The measurement of the air flow rate is the most common method in practice, by using rotameters and cross-sectional or bubble flow meters. 

While simple mechanical fiHing-level meters such as dipsticks and inspection glasses are reliable and accurate, they are not suitable for transmitting measured values. A cheap and reliable method is bubble-through measurement (Figure 2.8-4), which in principle measures the hydrostatic pressure and thus transforms the measurement of level into the measurement of pressure difference, which can readily be... 

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