BS EN ISO 4022:2018 pdf – Permeable sintered metal materials – Determination of fluid permeability (ISO 4022:2018).
1 Scope This document specifies a method for the determination of the fluid permeability of permeable sintered metal materials in which the porosity is deliberately continuous or interconnecting, testing being carried out under such conditions that the fluid permeability can be expressed in terms of viscous and inertia permeability coefficients (see Annex A). This document does not apply to very long hollow cylindrical test pieces of small diameter, in which the pressure drop of the fluid in passing along the bore of the cylinder might not be negligible compared with the pressure drop of the fluid passing through the wall thickness (see A.5). 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 2738, Sintered metal materials, excluding hardmetals — Permeable sintered metal materials — Determination of density, oil content and open porosity 3 Terms, definitions, symbols and units For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https://www.iso.org/obp — IEC Electropedia: available at http://www.electropedia.org/ 3.1 Terms and definitions 3.1.1 permeability ability of a porous metal to pass a fluid under the action of a pressure gradient 3.1.2 test area area of a porous metal normal to the direction of the fluid flow 3.1.3 thickness dimension of the test piece in the direction of fluid flow Note 1 to entry: For flat test pieces it is equal to the thickness. Note 2 to entry: For hollow cylinders it is given by Formulae (2) to (6).
4 Principle Passage of a test fluid of known viscosity and density through a test piece, and measurement of the pressure drop and the volumetric flow rate. Determination of the viscous and inertia permeability coefficients, which are parameters of a formula describing the relationship between the pressure drop, the volumetric flow rate, the viscosity and density of the test fluid and the dimensions of the porous metal test piece permeated by this fluid. 5 Test piece Before testing with gas, all liquid shall be removed from the pores of the test piece. Oil and grease shall be removed by using a suitable solvent with the extraction method given in ISO 2738. The test piece shall be dried before testing. 6 Apparatus 6.1 Equipment The choice of apparatus is mainly dictated by the size, shape and physical characteristics of the test piece. This document refers to two different types of apparatus suitable for determining the fluid permeability of porous test pieces. 6.1.1 Guard ring test head for flat test pieces. This is a type of test apparatus which is recommended for carrying out non-destructive testing of partial areas of flat porous sheets. The permeable metal sheet is clamped between two pairs of flexible seals. The inner pair, corresponding to the test area, has a mean diameter of D 1 . The outer pair, of mean diameter D 2 , forms a guard ring surrounding the test-area, which is pressurized to prevent side leakage from the test area (see Figure 1).
The guard ring test head minimizes side leakage by ensuring that the pressure is the same in the inner and outer chambers. On the upperstream face of the test piece, this is achieved by arranging that the port area connecting the upper chambers (as shown in Figure 1) is as large as possible. On the downstream face of the test piece, the inner chamber leads to a flowmeter, usually subject to a small back pressure, and the outer chamber leads to atmosphere via a pressure-equalizing valve. This valve is adjusted to equalize the pressure in the inner and outer chambers. The fitting of a restrictor between the test piece and the flowmeter, to increase the back pressure and thus permit more stable control of the pressure-equalizing valve, is allowed. However, ideally, the pressure on the downstream face of the test piece should be as near as possible to atmospheric pressure and a restrictor should not be used unless necessary for the adjustment of the pressure drop in the flowmeter. Toroidal sealing rings (“O”-rings) are recommended for the inner seals. The seals shall be sufficiently flexible to overcome all surface imperfections and lack of flatness of the porous metal. In some instances it might be necessary to load the inner and outer seals separately to ensure leak-free sealing. Two upper and two lower seals are required and these shall be in line with each other.