Discussion on “failure of disk insulators on high-tension transmission”

R. J. C. Wood: There is a very interesting thing in Table 3. In the early years we find that the No. 1 disk is the one which is failing to the greater extent, in 1913, 1914, 1915, 1916; and then in 1917 No. 7, which is the one nearest the point of support, usurps first place and keeps approximately that position, so that on the whole in these latter years it is the one nearest the point of support which shows the greatest number of failures. Now we all know that in the years 1913, 1914, the kind of insulator we were getting was very different from the insulators we get today; and that raised the question in my mind as to whether those early failures may not have been due to one cause — perhaps soft, porous porcelain, which was to be had in plenty; and the failures of the later years, when it is to be presumed that most of that poor stuff had been weeded out, have been caused by prolonged mechanical vibration.