Soap-bubble method

Immediately after the running test, any compressor intended for toxic, hazardous, flammable, or hydrogen-rich service should be gas tested with an inert gas to the maximum seal design pressure. The test is held at least 30 minutes and the casing and its joints checked for leaks, using a soap bubble method or other suitable means for leak detection. When no leaks are detected, the compressor will be considered acceptable. 

As in the soap bubble method, only fast flames can be used because the adiabatic compression of the unbumed gases must be measured in order to calculate the flame speed. Also, the gas into which the flame is moving is always changing consequently, both the burning velocity and flame speed vary throughout the explosion. These features make the treatment complicated and, to a considerable extent, uncertain. 

There are of course a number of methods that can be classific d a- methods for the visualization of airflow and contaminant dispersion. This i.hapter describes some of these that are useful for designers of industrial vcntilatiou. Methods that not are presented in more detail here are, for example, to fill small soap bubbles or ordinary balloons with helium in order to stuiiy the airflow field in large rooms. A large number of textbooks focus on flow- visualization. The research in this area can also be followed in The lournal of Floif Visualization and Image Processing. -... 

Use of the helium test method will result in considerable increases in efficiency (cycling times being only a matter of seconds in length) and lead to a considerable increase in testing reliability. As a result of this and due to the EN/ISO 9000 requirements, traditional industrial test methods (water bath, soap bubble test, etc.) will now largely be abandoned. 

It is also practically constant if the gas, enclosed in a soap bubble, is ignited in the center by means of a small electric spark (Method of Stevens, as described in Ref 13, p 384). In this case a spherical flame front is created and as resistance of soap film is very small, the pressure and burning rates are practically constant... 

In an effort to eliminate wall effects, two spherical methods were developed. In the one discussed here, the gas mixture is contained in a soap bubble and ignited at the center by a spark so that a spherical flame spreads radially through the mixture. Because the gas is enclosed in a soap film, the pressure remains constant. The growth of the flame front along a radius is followed by some photographic means. Because, at any stage of the explosion, the burned gas behind the flame occupies a larger volume than it did as unbumed gas, the fresh gas into which the flame is... 

Figure 11.6 SEM images of polypyrrole microcontainers synthesized electrochemical ly using a soap bubble -assisted soft-template method. (Reprinted with permission from Chemical Communications, Electrochemical synthesis of novel polypyrrole microstructures by L. T. Qu and G. Q. Shi, 2003, 2, 206-207. Copyright (2003) Royal Society of Chemistry)...

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. 

Polyferrocenylsilanes can be fabricated into films, shapes, and fibers using conventional polymer processing techniques. The dimethyl derivative 3.22 (R=R = Me), which has been studied in the most detail, is an amber, film-forming thermoplastic (Fig. 3.7a) which shows a Tg at 33°C and melt transitions (T ) in the range 122-145 °C. The multiple melt transitions arise from the presence of crystallites of different size, which melt at slightly different temperatures [65, 100). Poly(ferrocenyldimethylsilane) 3.22 (R=R =Me) can be melt-processed above 150°C (Fig. 3.7b) and can be used to prepare crystalline, nanoscale fibers (diameter 100 nm to 1 pm) by electrospinning. In this method, an electric potential is used to produce an ejected jet from a solution of the polymer in THF, which subsequently stretches, splays, and dries. The nanofihers of different thickness show different colors due to interference effects simUar to those seen in soap bubbles... 

The determination of the volumetric flow rates is easily performed by a flowmeter and a stopwatch (by soap-film method). It is necessary to consider the pressure drop when the gas bubbling through the saturator to yield calibration curves as a function of the soap-film burette method. 

The pressure measurement, achieved by use of the Textilpress device, is an indirect measuring method, which is based on die Laplace Law. Ltq>lace Law has been widely used to calculate the pressure delivered to a cylindo of known radius by a bric under known tension. However, this Law was originally developed by Laplace in 1806 to explain the surface tension phenomenon in liquids and their ability to form droplets or soap bubbles [6]. The Laplace Law is illustrated in Figure 3 and by equaticm (1). 

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