Bubble immersion test

Freon F12 loss per year (g/a) Time taken to form a gas bubble (s) Equivalent leak rate (cm3[STP]/s) Detection time using helium leak detector (s) 

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The bubble point test is a popular single-point physical integrity test for disc filter membranes based on Eq. (21). A fdter medium is wetted with a liquid, and test gas pressure is slowly raised until a steady stream of bubbles appears from a tube or hose attached to the downstream side of the filter and immersed in water (Fig. 9). The pressure at which the bubbles first appear is recorded as the bubble point and is related to the largest pores in the fdter medium. A pore size can be calculated from Eq. (21) however, it must be realized that the bubble point test does not measure the actual pore size, but only allows correla-... 

The bubble point test is based on the fact that, for a porous filter medium, immersed in and thoroughly wetted by a specific liquid, the pressure required to force a gas bubble through a pore is inversely proportional to the diameter of the pore. In practice, this means that the pore size of a filter element can be established by wetting the element completely with the liquid and measuring the pressure at... 

A typical rig for the bubble point test is shown in Figure 1.18. The sample of filter medium is immersed in a suitable liquid (often f-propyl alcohol), and air is forced into the interior of the sample from a reservoir until the first bubble is seen, at which point the air pressure is recorded. 

Various membrane materials are to be compared for corrosion resistance in hydrochloric acid. Membrane samples are ultrasonically cleaned with Freon for 5 minutes and dried at 200°C for 2 hours followed by similar steps of ultrasonic cleaning with demineralized water and drying. The conditioned membrane samples are then immersed in 35% HG solution, making sure that no air bubbles are trapped in pores. The acid exposure at the test temperature (e.g. 25°C) continues for a given period (e.g. one week). The tested samples are ultrasonically washed with demineralized water for 5 minutes and dried at 200°C for 2 hours. The weights of the cleaned membrane samples before and after the acid exposure are compared to assess the relative corrosion resistance of various membrane materials. 

Table 5.3 Comparison of bubble test method (immersion technique) wit helium leak...

The chemist inverts a test tube and immerses the open mouth into the reaction beaker to collect the hydrogen gas that bubbles up from the solution. The reaction proceeds to equilibrium. At the end of the experiment, the water levels within the tube and outside the tube are equal. The pressure in the lab is 101.325 kPa, and the temperature of all components is 298 K. The vapor pressure of water at 298 K is 3.17 kPa. What is the partial pressure of hydrogen gas trapped in the tube ... 

Pour about 350 ml of distilled water into a flask with a volume of 0.5-1 litre and saturate it with air by shaking it. Fill the flask of the apparatus and the gas-discharge tube with the water saturated with air. Close the flask, making sure that not a single air bubble remains in the flask and in the tube. Put a test tube filled with water onto the free end of the gas-discharge tube immersed in a bath with water and fasten it in a stand (the test tube and the stand are not shown in... 

Care must be taken to exclude air bubbles when weighing in water, and this is helped if a trace of detergent is added and/or the test piece quickly dipped in ethanol before weighing. If the rubber is less dense than water, then a sinker must be used in the same manner as for density measurements (see Chapter 7). The test piece is then immersed in the test liquid for the chosen time at the chosen temperature. At least 15 times the test piece volume of liquid should be used and care must be taken to ensure that the rubber is exposed on all sides to the liquid. This can be done by suspending the test pieces on wires or it is satisfactory to rest them on glass marbles. 

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-... 

SOD lead corrosion—test developed by Exxon to measure the corrosiveness of lubricating oils. A small lead panel of known weight and a copper panel (as catalyst) are attached to a spindle, which is immersed in a tube of the lubricant and rotated. Air is introduced at the bottom of the tube and allowed to bubble up through the sample. The weight loss by the lead panel after a specified period of time is a measure of the corrosivity of the oil. 

Sensitivity to initiation (30 mm diam cartridges)-grams of MF to cause complete deton at density (d), 0. 30g at d 0.85, 0.40 at 1.20, 0.50 at 1.40 and 2.5g at d 1.57 g/cc. In these same cartridges, cast R-Salt at d 1.42 reqd a Brisk a detonator for complete detonation (See also Vol 1, p XXIII) Sensitivity to initiation (by heat) - when 0.02g sample in a lOmm test tube was immersed 10 min in a molten metal bath and heated at 5°/min, melt-ing began at 105°, decompn began at 150°, nitrous gases evolved at 160°, and the sample was entirely decompd at 170°. When the tube was plunged into a bath at 300°, decompn was immediate, at 250° decompn was in 40 sec, at 200° in 2 min, at 150° decompn proceeded very slowly, at 110° some bubbles appeared but no increase in decompn occurred in 20 mins (See also Vol 1, pp XXII - XXIII) Specific work - See Coefficient d utilisation pratique... 

To evaluate the perfection of encapsulation, the coated pellets were immersed in pure methanol. Evolution of hydrogen from one or more points indicates the presence of a pinhole or other imperfection in the coating. Since the encapsulated pellets are denser than methanol, pinholes in individual pellets are detected easily by evolution of a stream of hydrogen bubbles rising from the pellet to the surface. Such pellets are removed. The test is continued for 15 minutes, and the percent of pinhole-free pellets is calculated. Typical data are presented in Table I. 

In llraidy s modification, which is stated to give more consistent results, 2 5 g. of very finely divided air-dry cotton is treated with a mixture of 5 c.c. of 10 per cent, copper sulphate (cryst.) and 95 c.c. of an almost saturatcd solution of sodium carbonate and bicarbonate g crystals and 50 g. bicarbonate made up to 1 litre). The cotton is immersed by means of a rod and the air bubbles are allowed to escape the flask is then surrounded with boiling water for exactly three hours. The contents arc filtered off on an asbestos filter and washed first with dilute sodium carbonate solution and then with water. Then the residual cuprous oxide is dissolved by treatment with a solution containing 100 g. of iron alum and 140 g. of concentrated sulphuric acid per litre. Two such treatments usually suffice. The fitter is tben washed with 2 Af-sulphuric acid the combined filtrate and washings arc titrated with A /25 potassium permanganate solution. According to Brissaud the test is affected by air. 

Alternatively, damage to the outer layers (epicuticle) may be revealed by means Allwbrden reaction [20]. When wool fibres are immersed in chlorine or bromine water, bubbles or blisters known as Allworden sacs are formed on the surface. Damage to the fibre surface may show up by lessening the size of or eliminating altogether, the blisters. This test is particularly useful when damage caused by alkali treatment is severe. 

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