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1、 AS 1774.72008 ISO 8841:1991 Australian Standard Refractories and refractory materials Physical test methods Method 7: Permeability to gases AS 1774.72008 This Australian Standard was prepared by Committee MN-007, Refractories and Refractory Materials. It was approved on behalf of the Council of Sta
2、ndards Australia on 7 October 2008. This Standard was published on 4 December 2008. The following are represented on Committee MN-007: Australasian Institute of Mining and Metallurgy Australian Aluminium Council Australian Ceramic Society Bureau of Steel Manufacturers of Australia CSIRO Manufacturin
3、g the time of cooling shall be at least 2 h. KEY 3a 3b I 1 Source of gas (compressed gas cylinder or water reservoir) 2 Desiccator for the gas 3 Floating flowmeters: (a) 0 to 200 cm3/min, (b) 200 cm3/min to 1 500 cm3/min 4 Holder for cylindrical sample 5 U-tube manometer, filled with liquid Figure I
4、 - Arrangement of instruments for measuring gas permeability (measured under a pressure head) KEY 1 Entry of the gas, via a desiccator 2 Holder for cylindrical sample 3 U-tube manometer filled with liquid 4 Floating flowmeters: (a) 0 to 200 cm3/min, (b) 200 cm3/min to 1 500 cm3/min 5 Woulff safety b
5、ottles 6 Regulating vent 7 Diaphragm or water pump Figure 2 - Arrangement of instruments for measuring gas permeability (measured under suction) For pressure measurement Figure 3 - Test piece holder 7 Procedure 7.1 Carry out a blank determination to establish that the test rig is gas-tight using an
6、impermeable dummy test piece (5.1.7) in the place of the normal test piece. 7.2 Measure the diameter and the height of the test piece to 0,l mm, using the Vernier callipers (5.1.5). 7.3 Place the test piece in the holder (5.1.2), en- suring that the pressure on the rubber membrane is sufficient to r
7、ender the cylindrical surface of the test piece gas-tight. This may be checked by increasing the pressure on the membrane; there should be no change in the pressure difference between the plane faces and no change in the rate of gas flow. 7.4 Determine the rate of flow through the test piece for at
8、least three different pressure drops across it. Calculate the permeability of the test piece for each determination. (See clause 8.) NOTE 8 These determinations are to verify that the rate of flow is proportional to the pressure drop, because the equation used for the calculation (see clause 8) is o
9、nly valid for laminar flow. 3 www.standards.org.au Standards Australia 3 www.standards.org.au Standards Australia IS0 8841:1991(E) 7.5 If the calculated permeabilities at the three different pressure drops differ among themselves by more than 5 %, repeat the blank test, check the equipment and repea
10、t the tests. If the repeat tests still differ by more than 5 */*, state this in the test report. 8 Expression of results 8.1 The permeability, expressed in square metres to two significant digits, is given by the equal-ion h 1 y=q2- AP - - yv-kv . . . (3) where )1 is the dynamic viscosity, in Pascal
11、 sec- onds? of the gas passed through the test piece at the temperature of the test; h A is the height, in metres, of the test piece; is the cross-sectional area, in square metres, of the test piece through which the gas has passed (see 7.2); 4 is the pressure difference across the test piece, in pa
12、scals; 4v is the rate of flow, in cubic metres per second, of gas through the test piece; k V is a correction factor (see table 1) for the removal of water vapour (used only if the air flow was measured by displacement of water). NOTE 9 For air temperatures from 16 *C to 24 *C the values for the dyn
13、amic viscosity of air (yj) are given in ta- ble 1, and these may be used under the assumption that the pressure drop over the test piece is small (see note 3 to clause 3). The values for the dynamic viscosity of nitrogen are given in table 2, from IO *C to 35 *C. 8.2 Equation (3) may be written in t
14、erms of the units more likely to be directly read in the test. Thus the value of the permeability, expressed in square centimetres, is given by 1) 1 poise = 0,l Pa-s 2) 1 mmH,O = 9,807 Pa h 4x106 1 4v P = 7 * - - - * 10 nd* 9,807 h is the height, in miilimetres, of the test piece; d is the diameter,
15、 in millimetres, of the test piece: Ap is the pressure difference across the test piece, in millimetres, of water column*); 4v is the rate of flow, in cubic centimetres per minute, of gas through the test piece; is a correction factor (see table 1) for the removal of water vapour (used only if the a
16、ir flow was measured by displacement of water). 8.3 If the alternative test piece size and holder is used (see 6.1 and 5.1.2), equation (4) will be modi- fied as follows: 4 x106 IO6 - is replaced by - nd* x2 where x is the side, in millimetres, of a cubic test piece. Equation (4) becomes I,70 x lo-
17、*hq, 2 x Ap -k, Table 1 - Dynamic viscosity of air Temperature OC Dynamic viscosity x 10e6 Pas 16 17,88 0,982 18 l7,98 0,980 20 18,08 0,911 22 18,18 0,914 24 18,28 0,971 4 4 4 www.standards.org.au Standards Australiawww.standards.org.au Standards Australia The Standard is downloaded from Standard S
18、haring IS0 8841:1991(E) Table 2 - Dynamic Tempe- Dynamic Tempe- Dynamic rature viscosity rature viscosity “C x lo-” Pa-s OC x lo-.” Pas 10 11 12 13 14 15 16 17 18 19 20 21 22 17,l 17,2 17,2 17,3 17,3 17,4 17,4 17,5 17,5 17,6 17,6 17,7 17,7 - viscosity of nitrogen 23 17,7 24 17,8 25 17,8 26 17,Q 27 1
19、9,Q 28 18,O 29 18,0 30 18,l 31 18,l 32 18,2 33 18,2 34 18,2 35 18,3 9 Test report The test report shall include the following infor- mation: a) the name of the testing establishment; b) the date of the test; c) a reference to this International Standard, i.e. “Determined in accordance with IS0 8841”
20、; d) a description of the material tested (manufac- turer, type, batch number, etc.); e) the number of samples tested for each direction of gas flow in the brick or item; f) the gas used; g) the separate pressure drops (pressure or . suction) across the test piece, and the corre- sponding rate of ga
21、s flow through the test piece; h) the mean value of the permeability of the ma- terial for each direction of gas flow (relative to the direction of pressing of the brick or item); i) reference to any variation in permeability be- tween the three different determinations which is greater than the per
22、mitted value (see 7.4 and 7 5) . . NOTE 10 The individual values are used for determining the mean value. The mean value is used for further stat- istical analysis, in accordance with the IS0 5022. 5 5 www.standards.org.au Standards Australia 5 www.standards.org.au Standards Australia NOTES 6 6 The
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