From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Specification detailing test procedures for untreated electrical insulating papers.
| Identifier | ExFiles\Box 24\2\ Scan240 | |
| Date | 30th January 1923 guessed | |
| ELECTRICAL INSULATING PAPERS (UNTREATED). 661 (4-12) of polished steel and compressed paper or cotton, arranged alternately, the former being heated. The paper is usually damped before passing through the super-calender. (d) Plate Glazing (P.G.). Plate Glazing is carried out by placing the paper between plates of polished copper and subjecting them to pressure. Note.—Plate glazing is chiefly confined to hand-made papers, superfine litho papers and the like. Machine Finish (M.F.). When paper is not glazed, a slightly smooth surface is imparted to it during its travel through the paper making machine. This is known as machine or mill finish. III. TESTS. The tests given below are recommended for the study of Electrical Insulating Papers. The Schedule at the end of the Specification indicates which tests are most appropriate for papers intended for the various specific applications shown. Clause No. | Schedule of Tests 1 Conditioning of Specimens for Test. 2 Determination of Thickness. 3 Determination of Density. 4 Tensile Strength and Extension. 5 Ageing (Bursting Test). 6 Tearing Strength. 7 Porosity. 8 Chemical Tests. (a) Moisture loss on drying at 100° C. (b) Acidity and Alkalinity. (c) Mineral Ash. (d) Sizing. 9 Chemical Tests for Metallic Particles. 10 Flash Test for Conducting Particles. 11 Crinkling under Tension. 12 Microscopical Examination. 1. CONDITIONING OF SPECIMENS FOR TESTS. Before the tests specified in Clauses 4, 6, 7 and 8 (a) are carried out, single sheets of paper shall be conditioned in a controlled atmosphere for not less than 18 hours. The controlled atmosphere shall have a relative humidity of 75 per cent and a temperature of 70° F.{Mr Friese} (21·1° C.). The specified relative humidity shall be obtained by the use of a solution of sulphuric acid in water, specific gravity 1·220. The paper shall be tested as soon as possible after removal from the controlled atmosphere, and in any case before 3 minutes have elapsed. Note.—The method of conditioning given above cannot be applied to paper in rolls, which must be cut up before conditioning. 2. DETERMINATION OF THICKNESS. The thickness of the paper shall be measured by means of a micrometer fitted with a rachet head. The measuring faces shall be not less than ¼ inch and not more than ½ inch diameter, and one face shall be free to swivel. The average thickness of the paper shall be ascertained as follows :— In the case of rolls, after the three outer layers have been removed a test-piece one foot long and the full width of the roll shall be taken. Ten measurements of thickness equally spaced diagonally across the test-piece shall be made. In the case of sheets, ten measurements equally spaced diagonally across the sheet shall be made. The maximum, minimum and mean values of thickness shall be stated. 3. DETERMINATION OF DENSITY. The density expressed in terms of weight in grammes per cubic cm of volume shall be ascertained by weighing and measuring, in an artificially dried atmosphere, samples, not more than 8 inches (20 cm) square, immediately after they have been heated at a temperature of 212° F.{Mr Friese} (100° C.) for three hours. 4. TENSILE STRENGTH AND EXTENSION. The paper shall be conditioned in accordance with Clause 1 before the tests for tensile strength and extension are carried out. For the purpose of the test for tensile strength and extension at least 12 samples for test shall be taken. Six of these shall be cut in the direction of the length of the paper and six across the width of the paper. The dimensions of each test-piece shall be ¾ inch wide by 10 inches long so as to give 6 inches clear between the testing jaws. The load shall be applied gradually, and the test shall be carried out in such a manner that the tensile strength in lb. per square inch (kg per sq. cm) sectional area, and the percentage extension on the original length under load, can be determined. In computing the tensile strength of the paper the mean thickness obtained in accordance with Clause 2 shall be taken. The maximum, minimum and mean values of tensile strength and of percentage extension shall be stated. For the method of determining the direction of “length” and “width” of paper when supplied in sheets, see Appendix. 5. AGEING (BURSTING TEST). The tendency of the paper to deteriorate with age shall be proved by a comparison of the bursting strength of the paper before and after it has been heated in a drying oven at a temperature of 230° F.{Mr Friese} (110° C.) for 24 hours. The paper shall be conditioned in accordance with Clause 1 before the bursting test is carried out in each case. The bursting strength of the paper shall be determined in accordance with the following method :— The paper shall be gripped on to a ring leaving a free circular membrane which shall be subjected to fluid pressure until it is broken. The value of the pressure required to break the paper, shown on an indicator attached to the apparatus, shall be expressed in lb. per square inch (kg per sq. cm). VOL. 60. 45 | ||