IEC 60667-2:2020 pdf download

IEC 60667-2:2020 pdf download.Vulcanized fibre for electrical purposes – Part 2: Methods of test
1 Scope
This part of IEC 60667 gives methods of test for vulcanized fibre sheets for electrical purposes. Material made by combining with an adhesive several thicknesses of vulcanized fibre is not covered by this document. Materials which conform to this specification meet established levels of performance. However, the selection of a material by a user for a specific application is based on the actual requirements necessary for adequate performance in that application and not based on this specification alone. Safety warning: It is the responsibility of the user of the methods contained or referred to in this document to ensure that they are used in a safe manner.
2 Normative reference
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. IEC 60641-2:2004, Pressboard and presspaper for electrical purposes – Part 2: Methods of tests IEC 60667-3 (all parts), Specification for vulcanized fibre for electrical purposes – Part 3: Specifications for individual materials IEC 61621:1997, Dry, solid insulating materials – Resistance test to high-voltage, low-current arc discharges ISO 178:2019 , Plastics – Determination of flexural properties ISO 287:2017, Paper and board – Determination of moisture content of a lot – Oven-drying method
8 Flexural strength
The measurement of the flexural strength is only applicable for materials applied to a nominal thickness of 10 mm or more. Flexural stress at rupture shall be determined as specified in ISO 178. The test pieces shall be from the sheet to be tested with their major axes in the directions indicated at LN and WN in Figure 4 of ISO 178:2019; five test pieces in each direction. If the sheet to be tested is more than 20 mm thick, the thickness of the test pieces shall be reduced to 20 mm by machining both faces symmetrically.
9 Water absorption
Three test pieces shall be 50 mm ± 1 mm square of thickness of the sheet under test. Dry three test pieces for 1 h in the oven controlled at 100 °C ± 2 K, and cool to ambient temperature in a desiccator. The mass of the test pieces shall be measured to an accuracy of 1 mg. Place the test pieces in a container containing distilled water, controlled at 23 °C ± 0,5 K. After immersion, remove the test pieces from the water and remove all surface water with a clean, dry cloth or filter paper. Re-weight the test pieces to the nearest 1 mg.
14 Flexibility (bending)
The flexibility is determined using the measuring principle depicted in Figure 1. A test piece is placed between the two jaws of the measuring device as shown in Figure 2. The jaws are closed until the test piece cracks or shows signs of rupture. The flexibility tester is a small vise with jaws about 50 mm wide with small projections about 25 mm from the top edge of jaws against which the ends of specimens are placed. The movable jaw is equipped with a pointer and scale arrangement to indicate the decimal parts for each complete revolution of the vise handle. A dial gauge graduated in 0,01 mm units is placed in the back of the vise handle to indicate the jaw movement for a part of a complete revolution of the handle. Measure the distance between the inner span of jaws by a dial gauge. Three measurements of each direction are made on the test pieces approximately 25 mm by 50 mm cut from both directions of specimens. Open the jaws of the bend tester to about 20 mm. Carefully insert a test piece (25 ± 1) mm × (50 ± 1) mm between the jaws in a slightly arched position brown side up.