March 31, 1916. THE COLLIERY GUARDIAN 607 usually designed, and calculations are based upon using mild steel conforming to the British Standard specifica- tion of 28 to 32 tons tensile for open hearth steel. Unless this quality is specified .and provision be made for inspec- tion and testing, there may possibly be a temptation, under the stress of keen competition, for the builder to purchase in the cheapest market, and possibly use basic Bessemer steel, which is very often softer in quality, and not usually accepted for this class of work. Soft material may result in buckling some of the numbers of the framing, which may eventually cause serious trouble. With regard to cages, the above remarks may equally apply/but great care should be exercised that the lugs for chain attachments should have an ample factor of safety, and be of such special quality of material as would be used in the case of drawbars and couplings. TABLE 2. TENSILE TESTS FOR WROUGHT IRON GRADE B. Section Dimensions 1 Tensile Strength, Tons per Minimum Elongation per cent. Test Piece B I Test Piece P. Minimum Contraction of Area per cent of Original Area As Rolled. Turn'd Down As Rolled. IT urn’d Down. Diameters or Sides up to : — ROUNDS and 3 •" 21 to 25 22 — - - 40 SQUARES. 9/16 in. ... 21 to 25 22 - - 40 S'" 21 to 25 1 25 I ~ - 40 1 in. 21 to 25 !. 25 22 1 — 38 ins ... ... ... I I 21 to 25 , 25 22 i 31 27 38 q ms. 21 to 25 24 22 i ' 30 26 36 2 ins. 21 to 25 - 1 21 25 36 2i ms 20 to 24 20 ; 24 36 3 ms. 20 to 24 19 - 23 34 3i ins. . 20 to 24 - 18 - 22 34 4 ins. 20 to 24 - 17 -- 21 32 Test Piece A. FLATS. 4 ins. wide and under, tested as rolled or mach- ined to q ins. wide x under 5/16ths in. thick 21 to 24 1 8 27 NOTE Ditto x 5/16ths in. to under \ in. thick 21 to 24 1 9 29 Flats over 1 inch thick shall comply with the tests applicable to a square bar hav- Ditto x i in. thick and over up to 1 in. thick inclusive 21 to 24 5 !0 31 ing a side equal to Over 4 ms. wide, tested as the mean of the two rolled or machined to adjacent sides of the q ins. wide x | in. thick and under .. 21 to 24 i 18 27 Ditto X over ^in. thick up to and including lin. thick 21 to 24 1 9 29 ANGLES, TEES, £ in. thick and under .. 21 to 24 15* 22 and CHANNELS Over | in. thick ... 21 to 24 17 24 PLATES. With the Gram | in. to J in. thick 20 to 24 12 J in. to | in. thick .». 20 to 24 IQ — Ac oss the Grain. f in. to J in. thick 17 to 21 4 — J m. to J in. thick 17 to 21 4 — Note.— 1 Ton = 2,240 lbs. With regard -to the light rails for underground, it is important that hard steel be used similar in quality to the British Standard quality for heavy rails. If mild steel quality is used—and this is not infrequent where the makers are not also makers of heavy rails—the rails will bend beneath the sleepers, causing a wavy track, which results in loss of power for hauling. Much heavier rails, varying from 20 to 40 lb. per yard, are now used for main haulage roads, but in many cases, the rails are badly designed, the material in the rail not being dis- tributed so as to give the greatest strength for the weight per yard. It is recommended here again that the British Standard be adopted for shape of rail and for quality of material. Standardisation as far as possible is bound to result to the advantage of the user and the manu- facturer. If a buyer purchases any other than the standard section, he must either continue to purchase from one maker or have varying shapes for the same weight per yard. On the other hand, all manufacturers ought to be in a position to supply standard sections if called upon. Chains for Cage Attachments. Practically all colliery managers are fully alive to the importance of obtaining the best quality that can possibly be obtained for this purpose. The iron should conform to the following tests :—Tensile, 22 to 24 tons per sq. in.; 25 to 30 per cent, elongation in 8 in.; and 45 to 50 per cent, reduction in area at point of fracture. The iron should also show a thoroughly fibrous fracture, and bars of lin. diameter and above should admit of bending cold through an angle of 180degs. After providing for the highest class of iron and the highest class of workmanship, the chains should be tested to the Admiralty proof strain, and afterwards care- fully examined link by link and a certificate demanded from the makers of the chain guaranteeing that the specified iron has been used in every link of the chain and that the most skilled workmanship has been employed. The certificate should also specify what strain the chain has been tested to, and also the mark used for distinguishing purposes. It is further necessary that a 3 ft. sample should be taken out of the chain and broken to destruction. The result, to be satisfactory, should not be less than 150 to 200 per cent, over the ’ Admiralty proof strain. The chains should then be joined up and retested to the proof strain. The breaking result should also be stated on the maker’s certificate. Admiralty Tests for Chains. Close-link Stud chain. chain. Tons Tons. Proof load in length of 15 fathoms.... 12 d2 ... 18 d'2 Destruction test or 3 links from chain... 24 d2 ... 27 d2 ' d = diameter of iron in chain in inches. The proof loads on close link and stud chain given above correspond to a stress of about 8 and 11| tons respectively in the iron. The Board of Trade rules are the same as the Admiralty, except that in the case of stud chain the destruction load is only 40 per cent, greater than the proof load on sizes 2 in. and over, as against 50 per cent, required by the Admiralty. The Admiralty overseers always expect to get destruc- tion tests well above those stated in the specification, and investigate the possible causes closely if the break- ing tests are running at all near , to the specification. The Admiralty specify that the iron from which their chains are made shall stand the following tests :— Tensile. Tons per sq. inch. Bars up to 2| in. dia........... . 23 2| in. to 2'9/16 in. dia. inclusive 22| Over 2'9/16 in. dia.............. 22 Elongation. On 8in. On 4in. dia. dia. Per cent. Per cent. .. 22 ... 26 .. 22 ... 26 .. 22 ... 26 An important point with regard to chains is the reduced strength per square inch of the iron in the chain, compared with the strength of the original bar. The tensile of, say, 22/24 tons is reduced in the chain to 18/19 tons per square inch, this reduction being due to losses in welding, coupled with the uneven strain on the chain. Effect of Fatigue. The question of fatigue in iron has been previously referred to. The effect of such fatigue, or continuous working, changes the structure from the closely fibrous to a coarsely crystalline condition, with a seriously diminished strength of chain or coupling, as the case may be. The Home Office regulations provide that all users of chains should frequently anneal the chains, in order to guard against this weakness, and prevent, as far as possible, any accidents. Such annealing, to be effective, must be carefully performed; the whole of the chain should be carefully brought to an equal tempera- ture, viz., bright red, not less than 850 degs. Cent., and allowed to cool slowly, preferably in dry sand or hot ashes; and in the case of chains for cage attachments, not more than six months should be allowed to elapse before annealing. Chains may fail from many causes other than quality or workmanship, such as unequal distribution of the material in its design or unequal load on each chain; but these are points of engineering efficiency which do not come within the scope of the paper. Corrosion. The relative corrosion of iron and steel is a highly controversial subject, but there are two theories gener- ally accepted as causes. One is the acid theory, advo- cated by Calvert in 1871, who found corrosion due to an acid moisture; and the other is the electrolytic theory, in which water is assumed to be an electrolyte, that is to say, a small proportion of its molecules are ionised, and iron passes into solution, to be subsequently precipitated as rust. Under ordinary atmospheric conditions, wrought iron is a material that will withstand corrosion, better than ordinary mild steel; but the softer and purer the steel, the better it will withstand corrosion. “ Armco iron,” with its almost absolute purity, natur- ally stands high in this respect, and as far as the author’s experiments and those of Dr. Stead have gone, TABLE 3. TENSILE TESTS FOR WROUGHT IRON. GRADE C. Section. Dimensions* Tensile Strength, Tons per sq. in. Minimum Elongation per cent. Test Piece B. Test Piece F. As Rolled. Turn’d Down As Rolled. Turn’d Down. Diameters or Sides up to:— ROUNDS and 3 21 to 25 18 i — — SQUARES. 9/16 in 21 to 25 18 — — — i in 21 to 25 22 — — — 1 in . 21 to 25 22 19 — ins. 21 to 25 22 19 ! 26 23 1| ins. ... ... ... 21 to 25 21 18 1 25 22 2 ins 21 to 25 — 17 : ' 21 ins 20 to 24 — 16 — 20 3 ms 20 to 24 — 15 — 19 3^ ins 20 to 24 — 14 — 17 4 ins 20 to 24 — 13 L2L Test Piece A. FLATS. 4 ms wide and under, tested as rolled or mach- ined to ins. wide x under 5/16ths m. thick 21 to 25 14 NOTE. Ditto x 5/16ths in. to under J, in. thick 21 to 25 15 Flats over 1 inch thick shall comply Mth Ditto x in. thick and over 20 to 24 the tests applicable to a square bar hav- up to 1 in. thick inclusive 16 ing a side equal to the mean of the two Over 4 ins. wide, tested as rolled or machined to adjacent sides of the Flat. 1| ins. wide X in. thick and under ... 20 to 24 14 Ditto X over ^in. thick up to and including lin. thick 20 to 24 15 ANGLES, TEES, | in. thick and under ... 21 to 25 12 and CHANNELS. Over in. thick .. 20 to 24 14 PLATES. With the Grain. in. to j in. thick 20 to 24 8 f in. to J in. thick 20 to 24 8 Across the Grain. f in. to § in. thick 17 to 21 3 | in. to J in. thick 17 to 21 3 Note.—1 Ton = 2,240 lbs. it may be said to be quite equal to wrought iron. In fact, in a damp, acid atmosphere, or acid moisture of any description, there is very little doubt that soft steel and “Armco iron” are quite equal to wrought iron. There are no doubt many collieries where corrosion is chiefly due to acid. If the colliery be a wet one, the acid may come from several causes, viz. :—(a) Natural acid reaction of the water; (b) acid or metallic salt reaction, due to oxidation of the sulphur in the coal. A typical case is that of the Woodhead Tunnel, on the Great Central Railway; water is continually percolating through, and takes up the sulphur from the smoke of the engines, forming sulphurous and sulphuric acids, which drop on to the rails and cause corrosion to such an extent that the rails have to be very frequently renewed. In damp pits the fine coal dust becomes wet, clings on to all iron surfaces, and the sulphur readily oxidises, and causes rapid corrosion. Discussion. The President said the paper they had just heard read was of the utmost assistance to everyone connected with collieries. Although collieries were very large users of iron and steel, it was questionable whether many managers had gone closely into the subject of their com- position. They were indebted to Mr. 'Simons for giving them a clearer insight into the various properties of the various classes of steel under consideration. He quite agreed that Mr. Simons was wise in leaving out the question of wire ropes from a general paper like that. Although it was one of the rnost important uses to which they -at collieries put steel, it was a special subject, and he hoped they might prevail upon some member who was acquainted with the use of steel for wire ropes to complete their knowledge of this subject by giving them a paper on the question. He was interested to note that steel was being used for wagon coupling chains, and the alternating tests which Mr. Simons put forward rather showed why this should be so. The alternating test for wrought iron was 230, for drawbar gear steel 359, and for Armco iron 322. With regard to Armco iron, he believed that this represented a new method of manu- facture, which was being exclusively carried on by the Shelton Iron, Steel and Coal Company. He had seen some of the material. It was certainly a wonderful development, and undoubtedly had a future before it. He should like to experiment with this material for some of the purposes for which they had been using iron or steel, and he had no doubt Mr. Simons would be pleased to indicate for what purpose it could best be tried. With regard to classification, he must plead guilty to the indictment that colliery managers specified B, double B, or treble B iron, without knowing exactly what they were getting in response to their application. There was another brand of iron he had personally specified—cable iron. He did not know whether that was supposed to be a quality above treble B. The standards Mr. Simons had given were a far better means of securing uniformity of material, particularly where quality was of the utmost importance. Another point in Mr. Simons’ paper was •that standardisation was bound to result to the advan- tage of the user and manufacturer, and that applied, not only to rails, but to every form of engineering. He was going outside the subject of the paper, but at the colliery with which he was connected, if they required a new steam pipe amongst the older pipes, it always meant special measurements—the size of the flange and the number of bolt holes varied—and it wTas impossible to alter a pipe without a drawing having to be made. In recent work he had made it a rule to specify the British Standard, so that any additions from any firm were bound to fit. Mr. Simons’ remarks with regard to the relative liability to rust of iron and steel were exceed- ingly interesting. He had not been able to make experi- ments on his own account, but he had always been given to understand that in using wrought iron wagon bottoms there was much less liability to rust deterioration than in using steel; but, perhaps, some member had compared the two. Prof. John Cadman, D.Sc., said the paper was really one of considerable value, and was full of most sug- gestive and useful information. There were two points which, to him, stood out very materially. It contained a great deal of highly technical material, but, at the same time, Mr. Simons’ method of treatment was such that it was put iin an intensely simple manner. Further, it contained the record of some very valuable research, which had a special application, to colliery practice, and in that respect they owed Mr. Simons a debt for having taken the trouble to specialise for their benefit. He should like to have heard Mr. Simons treat the question of wire ropes, because in dealing with a subject like wire ropes, on the one hand, they were compelled to adept the experience of the gentlemen who controlled the wire rope manufactories, and, on the other hand, were hemmed in by extensive Home Office regulations, which specified a period of time that might or might not be based upon scientific conclusions. Mr. Simons had called attention to the British Standard Committee, whose work was not too well known amongst colliery people. There was a sentence in the paper which should be repeated again and again, “ Standarisation, as far as possible, is bound to result to the advantage of the user and the manufacturer.” The country was suffering at the present time from the lack of standardisation and the lack of organisation, and it was >this type of w’ork which would carry us through. He moved a hearty vote of thanks to Mr. Simons. Mr. J. W. Hartley said that with regard to Armco iron ? he should like to know whether it was suitable for fire boxes for locomotives. Every engineer was interested in obtaining a substitute for copper, because it was very expensive. He emphasised the importance of annealing; no colliery manager or engineer paid suffi- cient attention to it. He had seen chains that had been in use for 50 years, and had never been annealed. He had had some experience of wire ropes, though not of the size used at collieries. He recalled that, in con- nection with sewage distributors, T%in. diameter wire ropes ran successfully for seven years. Then there was an accident, and one broke, but the rope with which it was replaced did not last for 12 months. With regard to the British Standard specifications, many people did not know that they existed, and it would pay an insti- tution such as that to make a resume of the reports so far as they concerned collieries, because the papers as a whole were too voluminous for ordinary use.