DETERIORATION IN FENCNG WIRE.

Matamata Record, Volume II, Issue 82, 16 May 1918, Page 4

DETERIORATION IN FENCNG WIRE.

Testing by Post and Telegraph Department. (J. Orchiston, M.1.E.E., Chief Telegraph Engineer.) Much loss to the farming interests throughout the Dominion has resulted during recent years from the use of cheap German and other low-grade fencingwire, which only had a life of half a dozen years or so. The loss can be safely placed at hundreds of thousands of pounds. Some time ago there was a considerable amount of investigation in the United States as to the cause of the rapid deterioration of modern yfire as compared to that produced formerly. The conclusion arrived at was that the “ chief reason for the deterioration was due to the admixture of manganese in the process of manufacturing the steel.” Each molecule of manganese left in the metal will set up local galvanic action with the result that the wire will become pockmarked, or flayed off in junks, as if some sharp instrument had been used to bite pieces out of the metal. Other impurities in the metal will, of course, all tend to its disintegration. The purer the metal, the less oxidation —in other words, the longer it will last. Prior to some forty years ago all wire was made of ordinary iron, but on the advent of what might be termed the steel era the manufacture of iron wire practically ceased. The cheaper steel wire also gained favor from the fact that it would stand a greater strain before stretching. After some years it was discovered that it was not so lasting as the previous iron wire. It then became the practice to largely galvanise fencing-wire, but even this did not make up for the impurities resulting from the cheaper methods of manufacture. The Germans seem to have led the way in regard to cheapness and poor quality; and British firms had to follow suit or simply lose the trade, as the average farmer had and has no means of telling one wire from another. The cheap German wire, from' outward appearance, looks just as well as, and, in fact, sometimes better than the superior British if article. I leave it to the farmers I themselves to judge how many have knowingly bought German wire because it was 10s a ton cheaper, and have been sorry for) themselves afterwards. The Post and Telegraph Department is, of course, the largest user of wire in the Dominion, and an outline of its experience

may therefore be of interest. In 1864 the General Government, commenced the erection of telegraph lines from Marlborough to Southland. A considerable quantity of the wire then erected is still in use, and what has been dismantled was principally on account of alterations to the route, etc. A great deal of the wire erected in both Islands during the “sixti.es” is still doing good work, and likely to last many years longer if left alone. After 1882 I observed a marked difference in the class of wire coming to hand, and subsequently learnt that it was steel, and that as the British Post Offico had agreed to take steel wire at a cheaper rate than the previous iron wire the manufacturers had practically ceased to make iron telegraph wire by the old process. The result is that the wire erected during the later “eighties” and “ nineties ” is not so good as that of the “sixties ” and “ seventies,” and most of it will have to be replaced before that erected during the earlier period. At odd times between the 3 T ears 1895 and 1910, when the supply of standard wire had run out, some fencing wire was purchased to complete pressing works. In one case such wire erected in 1905 began to fall down in 1911 and had to be wholly renewed*in, 1912 —a total life of only seven years —whereas, as already indicated, much of the fifty-three-year-old wire in the South Island is still serviceable. Naturally, one is apt to ask, Can nothing be done to remedy or check the use of such inferior material ? There is a very simple means of arriving at the approximate purity of the iron. The purer any metal is, the greater its electrical conductivity; consequently the more impurities, the poorer the conductor. Reckoning the conductivity of absolutely pure iron at 100 per cent, the best class of telegraph-wire is expected to represent 97 per cent from an electrical conductivity point of view. It is doubtful, however, if any steel wire can be obtained as high as this ; and the British Post Office Telegraphs has set the minimum standard as low as 87 per cent., which has been the minimum adopted in New Zealand. I am, however, of opinion that this too low, and it is proposed to raise the standard. The old telegraph wire erected in the “sixties” approximated 95 per cent. Some fencing wire tested by me has been as low as 50 per cent., which is a clear indication that such wire will have a short life. Some recent importations of a new class of iron wire manufactured in America has reached the 97-per-cent, mark, and it is anticipated that this wire will be good for at least fifty years, although the galvanizing does not comply with the specifications of the New Zealand Telegraphs. During the last seven years hundreds of tons of telegraph wire have been rejected in Wellington, much to the disgust of the manufacturers and their local representatives. . Although the purity of the metal is of primary importance from a lasting point of view, it is also desirable that the wire should be well galvanised; and I may here state I have never found any fencing wire which would comply with our departmental specifications in this respect. In so far as the tensile strength of the low-grade wire is concerned, little fault can be found with it when new—in fact, it will invariably bear a greater strain before stretching than the firstclass article.