EN 993-4-1995 pdf download.Methods of test for dense shaped refractory products —Part 4: Determination of permeability to gases.
if, in equation (1), ö is expressed in centimetres, A in square centimetres and Vin cubic centimetres (the units for the other quantities being unchanged), an alternative unit for permeability may be derived, namely square centimetres. However, since compound prefixes are not permissible, the conventional prefixes may be used only with the unit square metres. thus 10 cm2 = 10 121n2 = 1 jmn2
4 Principle
A stream of dry gas is passed through the test piece, and the pressure drop across the test piece is recorded for at least three different rates of flow. From these values, and from the size and shape of the test piece, the permeability of the material is determined by calculation.
5 Apparatus
5.1 General
The general layout of the apparatus is shown diagrammatically in Figure 1 and Figure 2. Figure 1 shows the arrangement for the passage of gas under pressure and Figure 2 for the passage of gas under suction. The connecting piping shall be made of glass in preference to rubber, and shall be as short as possible, so that the pressure loss in the apparatus is very small when compared with the pressure loss produced by the test piece.
5.1.1 Supply of gas (under pressure or suction), consisting of a reservoir of gas at constant pressure.
5.1.2 Test piece holder, with gas-tight seals at the sides of the test piece. Gas tightness shall be ensured by a rubber membrane that is inflated to a ,ressure of 0,2 N/mm2 to 0,4 N/mm2. See Figure 3.
NOTE Modifications will be required lithe alternative test piece size (see note to 6.1) i used.
5.1.3 Liquid manometer, of the U-tube type, for measuring the difference in pressure between the two faces of the test piece. The usual experimental precautions for this type of measurement shall be taken, so that the error in the pressure determination does not exceed I % (including error in reading column height, meniscus error, error in the verticality of the manometer, and measurement of the density of the manometer liquid). The pressure shall be determined close to one face of the test piece in the vessel containing the test piece holder (5.1.2).
NOTE A lower pressure reading may result when the pressure away from the test piece is determined in the connecting tubes.
5.1.4 Gas flow measuring equipment, consisting of a sensitive floating flowmeter calibrated for a given temperature and pressure of entry. The flowmeter shall be accurate to within 2 %. The flowmeter shall be calibrated periodically for the gas to be used, and only the middle section of its measuring scale shall be used.
For the measurement of permeability to air only, the rate of air flow is measured by the displacement of air by water, using a graduated cylinder device and a chronometer.
6 Test pieces
6.1 Dimensions
The test pieces shall he cylindrical, with diameter 50 mm ± 0,5 mm and height 50 mm ± 0,5 mm. The perpendicularity of the axis of the test piece to the faces, and the parallelism between the top and bottom faces of the test piece shall both be within 0,5 mm.
NOTE A 50 mm cube test piece may also be used where necessary. In this case the test piece holder (see note to 5.1.2) will need to be modified and the calculation of the results (sec 8.3) will be slightly different.
6.2 Preparation
The test pieces shall be cut in such a way that no material is included that was within 4 mm of a face of the brick or item. The direction in which the test pieces are cut, relative to the direction of pressing, shall he stated in the test report.
The faces shall be freed from dust formed during the cutting, by brushing under a jet of water following wet cutting, or by a jet of compressed air following dry cutting.
6.3 Drying
The test pieces shall be dried to constant mass in the drying oven (5.1.6) at 110°C ± 5°C. Before measurement, the test pieces shall be allowed to cool to room temperature in a desiccator; the time of cooling shall be at least 2 h.EN 993-4-1995 pdf download.