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).
Page discussing the properties, composition, and sources of insulating materials, particularly asbestos.
| Identifier | ExFiles\Box 24\2\ Scan107 | |
| Date | 25th January 1921 guessed | |
| - 20 - pitch, resins, sulphur, oils the already mentioned phenol resins, cellons etc. By this means it is achieved that the mechanically useful mineral fibres form together with the well-insulating and liquid resisting binding material a new body in which the disadvantages of the one substance are compensated by the opposing properties of the other. To such combination it is useful to add a few per cent of neutral loading materials in order to enchance the hardness of the material, its power to withstand the action of acids and make it more easily workable. As the binding material that is to be mixed with the asbestos fibres is usually soluble in alcohol, benzol or benzine the mixture is thoroughly stirred and the volatile components evaporated, the latter being regained for further use. At the same time any moisture contained in the mineral is removed. While the mass is still hot it is placed in cold moulds, or the product is allowed to cool off and is then pressed in hot moulds into the desired shapes. There are numberless varieties of the insulating material. Just mentioned, the names of which cannot all be mentioned. The products of different firms vary considerably in their properties and great care must be taken in selecting them. This has already been pointed out by Hakansson in his treatise on plastic insulating materials (elektrotechnische Zeitschrift 1910, Hefte 38 and 39) and the conditions have not been thoroughly changed even to the present day. There are still factories of electrical insulating asbestos products that work without a technically trained staff and are on this account neither in a position to test the properties of their products nor to know the requirements of different branches of electrical manufacture according to the variety of purposes for which the dielectric is to be used. The announcements in the price list of such firms have no meaning unless the methods of working in the factory are known sufficiently well to the consumer from a reliable source. I am forced to agree with Hakansson and confirm that the designer or manager of a generating station has every cause to have the greatest mistrust in choosing insulating materials from amongst the varieties of compressed asbestos. Asbestos is a mineral that is found everywhere but particularly in three places. These chief places are Canada, The Ural, and South Africa. In Canada the asbestos is found enclosed in serpentine rock and the mineral is obtained from deep mines with the use of explosives. The product is sorted according to its asbestos content and is passed through crushing machines, in which the fibre is separated out. It is customary to reckon that the stone contains about 3 to 7% of asbestos. contd. | ||