March 5, 1915. THE i COLLIERY GUARDIAN.; 503 Some Notes on the Explosion at Wharncliffe Silkstone Colliery.* By L. T. O’SHEA, B.Sc. (London).! An explosion of firedamp occurred at Wharncliffe Silkstone Colliery, near Barnsley, on Saturday, May 30, 1914, resulting-in.the death of 12 men. This accident has been the . subject of an exhaustive report to the Home Secretary by Messrs. S. Pope, K.C., and T. H. Mottram, H.M. divisional inspector of mines, in which the circumstances of the accident are stated in detail.! It is, therefore, only necessary to state that on the above date the colliery fan was stopped at 1.30 p.m. for 15 minutes, and about 1.50 p.m. an explosion occurred in the Whinmoor seam at the face, where an electric- ally-driven coal cutter was working at the time. There are two questions in connection with the explosion which seem to the writer to be worthy of special atten- tion, and in discussing these he hopes it will be under- stood that it is not his intention to discuss or criticise the official report. The two questions are : (1) The rapid accumulation of gas in a small area during the stoppage of the fan; and (2) the development of the explosion. Accumulation of Gas. The Whinmoor . seam, in which the explosion occurred, is a thin seam lying about 65 yds. below the Silkstone, and is about 2 ft. 10in. thick. It is worked by undercutting with coal cutting machines on the “end” of the cleavage, in faces about 160yds. long, with a gate in the centre, belt conveyors 80 yds. in length being used to bring the coal from >a face on either side of the'gate. The dip of the'seam is about 1 in 12, and in the direction of the end faces. One belt is Table I.—Results of Analyses of Samples of Air from Wharncliffe Silkstone Colliery. Samples over machine to dip of J. T. Fisher’s gate. Samples taken at the top of William Fisher’s gate. Time. Gas shown on lamp. Percentage of inflammable gas over machine. Fan. Remarks. L’ime. Gas shown on lamp. Percentage of inflammable gas at roof. Fan. Remarks. P.m. 3.56 Nil. 0’075 Running- P.m. 3.56 Nil. 0’075 Running — 4.4 Nil. 0’416 Stopped. Ribbons at rest 4.0 4.4 Nil. Nil. 0T55 0’199 Stopping Stopped. Samples taken as fan stopped. Ribbons at rest at 4.8 Just slmwing 1’617 and anemometer stopped. Very slight dif- 4.6^ 4.8 ' — 9’141 4.3 p.m. Slight s m ell of gas. 4.12 on reduced flame held in roof. Slight cap 1’557 fusion. I >, * 4.10 4.12 Slight cap with lamp on dinting. 19’464 — — 4.15 about H per cent, at roof. About 2 per 1’389 4.13 4.14 4.14$ Cap Jin. Cap increased. Cap 1 in. — — 4.17 cent. Cap elongated. 1’387 Moving. Ribbons began to 4.15 4.16 4.17 Cap at top of glass. 19’322 17’077 Ribbons began to •move. Lamp removed from dinting to floor of gate. Sample taken 15 4.19 Cap spire 1 into 7’693 move. Explosive ; lamp 4.18 4.19 Extinguished 37’197 Ribbons increased move- ment. sec. after the ribbons began to move. Another lamp 4.19| 4.20 gauze. Extinguished. 14’276 19 767 removed to dint- ing. Non-explosive. 4.20 on floor of gate. 11’449 with large flame remained burn- ing. Al] in full swing. 4.21 — 13’395 >> — Note.—The analysis of the samples cont ining high percentages of gas showed that pro* ably a very small percentage of some higher hydrocarbon than methane was present, but probably not sufficient to affect explosibility. therefore to.the rise and the other to the dip of the gate. The belts and coal cutting machines were at the time of the accident driven by continuous current at a pressure of about 420 volts at the face. The motors of the conveyors were totally enclosed,- and the drums were driven by worm gearing running in oil (Spence’s patent). The motors of the disc coal cutting machines (Clarke, Steavenson and Company’s) were enclosed in cast steel rectangular boxes, with closely fitting joints. The breadth of the Athersley district of the Whinmoor seam is 950 yds. between the faults which bound it to the rise and to the dip. This distance is divided for working purposes into four faces, which are numbered, from the rise, 1, 2, 3, and 4. The explosion took place at the top of No. 2 face. It should be mentioned that in No. 1 face compressed air coal cutting machines were used at a matter of precaution, because a certain amount of gas was usually found near the fault at the top end of No. 1 face, the highest point in the field. The management had thus recognised and intended to provide for any natural ascensional accumulation of ^as from the goaves= The ventilating current in the faces in question usually * From a paper read before the Midland ■ Institute of Mining and Mechanical- Engineers. . f Professor of Applied Chemistry in the University of Sheffield. + Cd. 7720, 1914. Colliery Guardian, December 11, 1914, p 1217. contained abopt 0’5 per cent, of methane. The usual ventilating current in this district was 20,300 cu. ft. of air per minute. The percentage of methane in the return airway for the whole district was 0'7. There is, therefore, a total amount of firedamp normally produced in the district of 0*7 x 20,300 x 60 = 8,526 cu. ft. of fire- damp per hour. The ventilation is produced continuously by a Capell fan driven by duplicate engines of 250-horse power—one a tw’o-cycle gas engine,, the other a steam engine. In order to ascertain the effect of stopping the fan on the accumulation of gas at the coal face, two series of experiments were made by repeating the stoppage, one by H.M. inspectors .four days after the explosion,* the second by Prof. F. E. Armstrong and the writer on June .13, 1914 (Table I.). The results obtained by the writer generally agree with those of H.M. inspectors, and show the remark- able rapidity with which the gas accumulated in a still atmosphere, at the highest point to the rise. The difference in level between the position of the coal cutter and the top of William Fisher’s gate is about 5| ft. During the stoppage at least 19 to 20 per cent, of gas accumulated there, whereas at the roof at the .top of J. T. Fisher’s gate in the face the safety lamp only showed 2 per cent. 15 minutes after the fan stopped; whilst over the coal cutter not more than about 14 per cent, was found by analysis at the end of the stoppage. The results also show that during the accumulation of gas in the top corner of the face the amount at the machine midway between the dinting and the roof did not exceed 1*6 per cent, at any time. The rapidity with which the gas was swept forward after the fan started is also shown. At William Fisher’s gate the percentage of methane rose from 17 to 37 in two minutes, and at the machine from 1’4 to 7’7, 14, 19’75 per cent, in 3, 3-J, and 4 minutes respectively. The rapid increase at the top of William Fisher’s gate from 17 to 37 per cent, seems to indicate that a still larger percentage must have accu- mulated in William Fisher’s gate. The results of the experiments are in general agree- ment with those of the inspectors, any difference being those of degree. For instance, the inspectors found at William Fisher’s gate an accumulation of gas midway between the roof and floor of 5’25 per cent, four minutes after the fan stopped, whereas the writer obtained only 0’199 per cent, at the roof. The explanation is pro- bably that the face had been standing since the explo- sion, and the writer’s experiments were made 10 days later, so that the gas had had time in which to drain off. When the fan started at 2.16 p.m. the inspectors found 30-45 per cent, of gas, which rapidly fell to 5’82 per cent, at 2.20. The writer found 19’32 per cent, of methane at 4.15, which fell to 11’45 per cent, at 4.20. In explanation, it may be- stated that when the inspectors’ experiments were made the change was from ‘ the steam engine to the gas engine, whereas in the * See Colliery Guardian, December 11, 1914, p. 1219. writer’s experiment it was from the ‘ gas11 engine to the steam engine. The. gas engine' reaches its maximum speed more quickly'than the steam en'gihb, and hence the accumulation of gas would bo more rapidly'diluted. The Development of the Explosion. The area affected by the explosion;was'-small, being confined practically to the district bounded by the No. 2 level main haulage road, No. 4 topside slant, William Fisher’s gate, and the coal face from D to Stanley’s slant. There is no doubt in the writer’s mind, that the explosion originated in an ignition of methane, in the face. How and where the ignition was.> effected, the writer does not intend to discuss. . The jury at the inquest found .that the .ignition took place/at the coal cutter. Accepting this as correct for! the moment, it seems possible to trace what happened- on the day of the explosion from the experiments made on the effect of stopping the fan. There would be a very large accumulation of gas from the freshly exposed coal at the top corner of the face, and in William Fisher’s gate. The escape of gas would be greater than on the occasion of either set of experiments. It also appears probable.. from the experiments made on June 13, 1914, that mo indications of gas would be obtained..at thq eutter; or, assuming that there were indications, the ; quantity would not be sufficient to form an explosive mixture. When the fan started the gas would be rapidly pushed along the face from the corner, to the coal cutter, for in the experiment made on June 3, 1914, 30’45 per cent, of methane was found in..'the air'at William Fisher’s gate directly after starting the fan; and in those of June 13, 37’2 per cent. This would show that the gas penetrated into William Fisher’s gate, and was r. carried forward by the ventilating current. These mix-’’J tures contained respectively 13*99 per cent, and 12’8 per cent, of oxygen, and would, not be. inflammable. .. The mixtures were not, however, pushed forward in a f. body, but rapidly diluted wTith air, for the experiments, . made by the writer show that whereas there was 37’2 per cent, of methane at William Fisher’s gate at'4.18, i at 4.-19 (two minutes after the fail'started), there-was' 7’7 per cent, of methane over, the cutter, which increased to 19’7 per cent, at 4.20, :and then-,fell to 13’4 . per cent, at 4.21. Any one .of these mixtures could ,; have been ignited by sparks from .the machine, as the quantities of oxygen present, were 19’2, 16’4, and 17’8 per cent, respectively. It,is unreasonable to suppose ■ that, as the gas travelled down the .face-, it would become 1 ■ more and more diluted after passing the. machine. ; What - : the writer means is that you had a mixture of gas and air ' - containing a high percentage of > gas, which ' was -being pushed forward, and at the same time being diluted with the air that was coming on, so it’would be diluted with the air into which it went, and consequently the mixture would get more and more dilute as it passed down the face towards the No. 2 level main haulage road. r . ; , ■ , , It is clear to the writer that , whatever accumulation of gas occurred on the day of. the explosion,, it was driven forward and rapidly diluted.- Tt is.^possible that. , on the day of the explosion the accumulation of gas - was so, great that the first mixtures to meet the source of ignition were so deficient In. oxygen as to be non- inflanimable, but in a very short time inflammable mixtures would reach it; these would ignite,, and the , flame pass both up and down the face,, whether with . explosive violence or not would depend, on the propor- tions of methane and oxygen. Assuming that the pro— portion of methane was so high as not to .be explosive, a large volume of flame would he-formed. -■ If the course, •of the flame passing down the face were traced,- it would prove to be travelling in-am; atmosphere .into which a rapidly diluting mixture of-methane and'air was being forced, and at last would reach a-point when‘the mixture ' was highly explosive. Then the character: of the com- bustion would change, and explosive’violence develop, which would be intensified by any coal dust that, happened to be present. If the writer’s conception is correct, then evidence of burning and little damage ought to be found in the roadways to .the rise side of the ignition, whereas to the dip the effect of. explosive . violence should be found. An examination of the con- ditions of the district .seems - to show an agreement ' with the above suggestion, for, starting from the posi- tion of the machine, very little‘danffige wks done along ; the face to the rise, no props being blown out along the face. A small fall of roof in the slant and a door and hurdle sheet blown down in J. T. Fisher’s gate were the only.signs of explosive violence. There is evidence, however, of flame having passed in this direction in William Fisher’s gate, and as far as about 25 yds. down the slant. This seams to agree With the suggestion that if ignition took place at the machine, the mixture was not such as to produce explosive violence... Tracing the. course of the explosion to the dip, no mechanical damage was done along the face for a distance of about 60 yds., but the bodies of six of the .. victims showed considerable evidence ■ of .burning. Beyond this point props were blown out along the face, and considerable explosive violence developed along No. 2 level, which ceased when it reached a wet zone at the junction of the level and the slant. The conditions seem to point to the fact that an explosion of gas was developed some distance from the machine to the dip, and was continued apparently by a dust explosion along the level until stopped by a wet zone,. . , . There is one point which seems to caff for, explana- tion, namely, the blowing out of the. doors in J. T. Fisher’s and the dummy gates. In J. T. Fisher’s gate the door was blown open and bent; in the dummy gate a portion of the door was -blown out-bye, and a portion in-bye. The writer believes that these were, blown out., as a result of the concussion produced bv.the explosion, , for, so far as he knows, there is no evidence of . flame passing down these gates. With regard to the accumulations 'of gas, the writer would emphasise the point of-the rapid accumulation to-