IEC 60811-504 pdf download

IEC 60811-504 pdf download.Electric and optical fibre cables – Test methods for non-metallic materials
4 Test method
4.1 General This part of IEC 6081 1 shall be used in conjunction with IEC 6081 1 -1 00. All the tests shall be carried out not less than 1 6 h after the extrusion or cross-linking of the insulating or sheathing compounds. Tests shall be carried out at the temperature specified in the relevant cable standard. For tests on the insulation, the test is intended for insulated conductors of circular cross- section having an external diameter up to and including 1 2,5 mm and for sector-shaped cores where it is not possible to prepare dumb-bells. For tests on sheaths, the test is intended for cables with an overall diameter up to and including 1 2,5 mm; and for flat cables, with a major axis dimension up to and including 1 2,5 mm. If required by the relevant cable standard the test shall also be carried out on larger cables. Note that equipment may need to be modified in accordance with the cable standard. Otherwise, the insulation and sheath of larger cables shall be subjected to the elongation test described in IEC 6081 1 -505.4.2 Bending test at low temperature for insulation 4.2.1 Sampling and preparation of test pieces Each core to be tested shall be represented by two samples of suitable length. After removal of the coverings, if any, the samples shall be used as test pieces. 4.2.2 Apparatus The apparatus recommended for this test is represented in Figure 1 , with explanations. It consists essentially of one revolving mandrel and guiding devices for the test pieces. Other single-mandrel apparatus, substantially equivalent to the one represented in Figure 1 , may also be used. The apparatus shall be located in a suitable low temperature cabinet before and during the test. 4.2.3 Procedure The test piece shall be fixed in the apparatus, as shown in Figure 1 . The apparatus with the test piece in position shall be maintained in the suitable low temperature cabinet at the specified temperature for a period of not less than 1 6 h. The cooling period of 1 6 h includes the time necessary for cooling down the apparatus. If the apparatus has been pre-cooled, a shorter cooling period is permissible, but not less than 4 h at test temperature. If the apparatus and test specimens have been pre-cooled, a cooling time of 1 h after each test piece has been fixed to the apparatus is sufficient. At the end of the prescribed time, the mandrel shall be rotated, in accordance with the conditions specified in 4.2.4, the test piece being guided so that it is bent tautly round the mandrel in a close helix. In the case of sector-shaped test pieces, the circular “back” part of the test piece shall be in contact with the mandrel. Afterwards, the test piece, still on the mandrel, shall be allowed to attain approximately ambient temperature.The actual diameter of each test piece shall be measured by a vernier calliper, a micrometer or a measuring tape. For sector-shaped test pieces, the minor axis is taken as the parameter equivalent to the diameter for determining the mandrel diameter and the number of turns. For flat cables, the mandrel diameter shall be based on the minor axis dimension of the test piece, which is wound on with its minor axis perpendicular to the mandrel. 4.2.5 Evaluation of results At the end of the procedure described in 4.2.3, the test pieces shall be examined while still on the mandrel. The insulation of both test pieces shall not show any cracks when examined with normal or corrected vision, without magnification. 4.3 Bending test at low temperature for sheaths 4.3.1 Sampling and preparation of test pieces For each sheath to be tested, two pieces of cable of suitable length shall be taken. Before starting the test, any covering shall be removed from the sheath. 4.3.2 Apparatus, procedure and test conditions In accordance with 4.2.2, 4.2.3 and 4.2.4, for cables having an armour or a concentric conductor under the outer sheath, the diameter of the mandrel shall be as specified in the cable standard for the type of cable. 4.3.3 Evaluation of results At the end of the procedure described in 4.2.3, the test pieces shall be examined while still on the mandrel. The sheath of both test pieces shall not show any cracks when examined with normal or corrected vision, without magnification.