1937 – Official Report into the Disaster
on the Causes of and Circumstances attending the Explosion
which occurred at Markham Colliery, Derbyshire,
on the 21st January, 1937
By J. R. Felton, O.B.E.
H.M. Divisional Inspector of Mines
Presented by the Secretary of Mines to Parliament
by Command of His Majesty
Table Of Contents
|Description of the colliery|
|The Blackshale Seam|
|Conditions before the explosion|
|Narrative of the explosion and rescue operations|
|Cause of the explosion|
|Appendix — List of persons killed|
|Plan No. 1. — General Plan of the Blackshale Seam.|
|Plan No. 2. — Plan of 2’s and 9’s Face, Blackshale Seam.|
|Plan No. 3. — Face of Controller Compartment of Coal-cutter.|
To Captain Harry Crookshank, M.P.,
Secretary for Mines.
In accordance with your directions, I have the honour to submit the following Special Report on the explosion which occurred at Markham Colliery, No. 1 Pit, on the 21st January, 1937, by which seven persons were killed and five persons were injured. Of the latter, two subsequently succumbed to their injuries, making the total death roll nine.
Inquests on the bodies of the nine deceased men were held at the County Police Court, Chesterfield, before H.M. District Coroner (Dr. R. A. McCrea) and a jury on the 18th and 19th February, when the following were present :—
|Mr. D. N. Turner (Managing Director)||For the Staveley Coal and Iron Co. Ltd.|
|Mr. J. Hunter (General Manager)|
|Mr. R. Ringham (Agent)|
|Mr. L. W. Limb (Manager)|
|Mr. H. Hicken||For the Derbyshire Miners’ Association.|
|Mr. F. Lee, M.P.|
|Ald. J. S. Spencer|
|Mr. O. Wright|
|Mr. P. E. G. Mather (Solicitor)|
|Mr. J. R. Felton Divisional Inspector)||For the Mines Department.|
|Mr. J. Hall (Senior Inspector)|
|Dr. S. W. Fisher (Medical Inspector)|
|Mr. J. Cowan (Junior Electrical Inspector)|
|Capt. C. B. Platt (Suptg. Testing Officer)|
Evidence as to the cause of death in each case having been given by Drs. J. B. McKay and H. T. Herring, the circumstances attending the explosion were fully investigated, ample opportunity being afforded by the Coroner to all parties to bring forward any evidence relevant to the inquiry. In all 23 witnesses were examined.
At the conclusion of the Inquests the jury returned the following verdict :—
“The deaths were accidentally caused by an unforeseen combination of abnormal conditions, that is, an accumulation of gas which was exploded by a flame which escaped from a cutting machine box caused by a faulty replacement of the cover plate. The jury is satisfied that every precaution and provision has been and is taken by the Staveley Coal and Iron Co. Ltd. to ensure the safety of the men working in their mines”.
Description Of The Colliery
Markham Colliery is one of three large collieries owned by the Staveley Coal and Iron Co. Ltd., and is situated some five miles from Chesterfield. Mr. John Hunter is the General Manager for the whole of the collieries, Mr. R. Ringham being the Agent and Mr. L. W. Limb the Manager of the Markham Colliery.
This colliery comprises four shafts, of which Nos. 1 and 2 are downcasts, and Nos. 3 and 4 upcasts. Four seams are being worked, and coal from the Blackshale seam, in which the explosion occurred, is wound at No. 1 shaft.
Altogether the colliery employs 1,828 persons below ground and 410 on the surface.
Ventilation is produced by two Waddle fans, one at No. 3 shaft and the other at No. 4, and at the date of the last recorded readings the total quantity of air circulated in all seams was 189,500 cu. ft. per minute. For the Blackshale seam alone the quantity was 66,200 cu. ft. per minute.
Safety lamps were used throughout the mine. At the face electric hand lamps were in use, and a proportion of the workmen — in excess of that required by the General Regulations (Firedamp Detectors) of 1st May, 1935 — were provided with flame safety lamps and “Ringrose” automatic firedamp detectors. Further reference will be made to this matter later.
The colliery is wholly mechanized, the coal-cutters and conveyors being driven by electricity; shot-holes, however, are drilled by compressed air.
The Blackshale Seam
It was in the No. 2 Development Unit, South-East District, of this seam that the explosion took place. The seam lies at a depth of 700 yards from the surface, and has an average thickness of 4 ft. 3 in. with an overlying dirt band or “flamper” eight inches thick.
The No. 2 unit (see Plan 1) comprises a longwall face the length of which at the time of the explosion was 192 yards, viz. :— 72 yards on the left side of the main loader and haulage gate and 120 yards on the right of that gate.
In each bank there was a belt conveyor delivering to a gate end loader in the centre gate.
The loader gate was the main intake and, on reaching the face, the air split right and left, the right split returning down the right tail gate and the left split travelling partly by way of the left tail gate and partly by way of No. 9’s face, these two latter currents joining in the No. 2 return gate outbye of No. 9 left hand airway (see Plan 2). Two hurdle sheets placed in the left tail gate regulated the quantity passing down that gate and directed the air up into the ripping lip. No. 9 conveyor face had not been worked for some six weeks prior to the explosion.
The width of the loader gate between packs was 12 feet and of the tail gates ten feet, a face ripping six feet thick being carried in the former, and in the latter five feet thick.
The rate of advance of the face was about 25 feet per week, the depth of undercut being five feet, the cutting on this face being done by two machines. The sequence of operations is :— day shift — filling coal; afternoon shift — cutting and filling holings; night shift — ripping, turning over, packing and timber drawing. Shots are fired in both coal and rippings, the average number fired per day being 26 and 12 respectively; coal shots are fired on the day shift and ripping shots at nights.
On No. 2 face 37 persons were employed on the day shift, 20 on afternoons and 32 on the night shift. There was a deputy on each shift, and a shot-firer on the day shift.
The quantity of air entering this district as measured in the intake 100 yards from the face on 8th January and recorded in the air measurement book was 11,600 cu. ft. per minute, and on the same day the measurement in the right tail gate gave 2,800 cu. ft. per minute. No measurement was taken in the left tail gate or on the No. 9 face.
A month earlier the corresponding readings were 13,500 and 3,850 cu. ft. per minute respectively. At the inquest the head surveyor said these measurements were based on the actual velocities recorded by the anemometer and made no allowance for friction; when adjusted in accordance with the makers’ chart they would become 11,890 and 3,310 for the 8th January, and for the month of December the quantity in the intake would be 13,840 cu. ft. per minute.
During the three months preceding the explosion the presence of firedamp in the No. 2 unit was reported on twelve occasions as follows:—
It will be observed that most of these reports refer to the finding of firedamp in the left hand gate or gate lip, but that on the 17th and 18th January a small percentage was reported as “giving off at 2’s left rib side.” In evidence it was explained that the gas was being given off at roof breaks.
On the 11th November, Thomas Barley, a stallman working at the top end of the face, found a small percentage of gas in a pot-hole near the corner when inspecting at the beginning of his shift, and reported this to the deputy; it was cleared as stated in the deputy’s report.
In the general body of the air on this face no firedamp had ever been found, and evidence was given to show that at no time had the presence of firedamp been indicated on any flame lamp or automatic detector on the face: the occasions above mentioned refer to the finding of gas at breaks and/or pot-holes.
Conditions Before The Explosion
On the day of the explosion the day shift men were engaged in filling off the undercut coal and timbering up the face (steel props and bars used as supports) as the coal was extracted, 11 colliers and three contractors being in the left bank. The three contractors (one of whom was Frank Mansell) were normally employed in 9’s main gate — “scouring” a road through from the loader gate to the left tail gate — but had been sent into the left bank to deal with a “roll” which at the time was crossing that face. This roll partially cut out the seam and restricted the height in the bank, and these men (as were others on two previous shifts) were engaged in enlarging the area at this point.
The regular day shift deputy (Leslie Stevens) having gone to the Central Rescue Station for his quarterly practice, Willis Fish, a shot-firer and spare deputy, was in charge of No. 2 unit on the day of the accident. He arrived at the face about 7 a.m. and first examined the left bank and then the right bank; tests for firedamp, he stated, were made in the left bank at various places, including the wastes, the left tail gate lip, the left hand top corner and eight yards down 9’s face, but none was found. At that time he noticed a break over the coal-cutter, which stood in the top corner, but it was not giving off gas. Similarly the loader gate lip and the right bank were inspected and found clear.
At about 9.30 a.m. the deputy attended to some matters in the loader gate, and then proceeded by way of 7’s main gate up 2’s left tail gate to the face, The two regulator cloths in this gate were seen to be in order. From the tail gate he then proceeded into the top corner and travelled the whole of 9’s face, returning the same way to 2’s face and along the left bank of that face to the loader gate. There was then no fall on 9’s face and no gas was there found.
Later the right bank was again inspected as also was the right side airway to 6’s main gate, and thence he returned up the loader gate to the face spending some time with the shotfirer (John Dowds) en route.
On the face there were eight “Ringrose” automatic gas detectors, two in the left bank and six in the right bank; two of the latter had been taken in by men moved from other faces. There were also a number of flame safety lamps used as detectors on this face, of which at least four went into the left bank.
Having again examined the right bank another examination of the left bank was commenced about 1 p.m., starting from the loader gate. This examination extended to the top corner and 20 yards down 9’s face, also into the left tail gate a few yards, and all was in order as before, the ventilation taking its normal course and indicating no noticeable change, except that the break on 2’s face was a little more pronounced.
When the deputy left the top corner (at about 1.35 p.m. he estimated) Edmund Smith was the only man working there and he was setting supports. He had with him a “Ringrose” automatic gas detector which was hung on a bar within five yards of the corner and over the belt race. The coal in the top stints having been filled out, four men (including two of the deceased) were moved down near the roll to assist in filling off some remaining coal there. The deputy again went into the right bank and on his way saw the left bank coal-cutter men in the loader gate getting their trailing cable ready, after which he returned to the men near the roll and finally left them completing their timbering preparatory to going home.
Fish had once more gone down the right bank to see that all was being left in order at the end of the shift, and was about 40 yards from the loader gate when he felt a rush of air and heat, an interruption of the ventilation followed by smoke and dust; he saw no flame and heard no report.
John Dowds was the shot-firer on No. 2 conveyor face and between 6.45 and 11.30 a.m. on the day of the accident fired 22 shots, which included three shots in the roll on the left bank at about 9 a.m. In no case did he detect the presence of firedamp in his examinations before or after the firing of these shots. The nearest shot to the left tail gate was about 24 yards lower down the face, and this was fired at 8 o’clock. In the course of the shift he had no occasion to go into the top corner, nor did he go into the left tail gate.
When the explosion occurred Dowds was in the right bank about 25 yards below the loader gate; he felt a rush of wind down the face, but was not injured in any way.
The evidence of Dowds eliminates any possibility of the explosion having originated through the firing of a shot.
During the morning the left bank was also visited by the day shift overman, Albert Edward Brown. Starting from the loader gate at about 10 o’clock he travelled up the left bank as far as the top corner where he tested for gas and found none. He also went into the left tail gate where he found the hurdle sheets in order and the ripping lip clear of firedamp. One sheet was five feet from the lip and the second about four yards further outbye.
At that time the ventilation appeared to be satisfactory and taking its normal course. He noticed a “Ringrose” detector hung up about eight feet from the top corner, and there was also a flame safety lamp between the corner and the tail gate. After spending some time on the roads the overman returned to the pit bottom which he reached at 1 p.m.
The last man to leave the top end of the left bank before the explosion was Herbert Smith, a stallman on the day shift, and his evidence is of considerable importance.
Smith worked in the third stint from the top, i.e. almost opposite the left tail gate; he was supplied with a flame safety lamp, as well as an electric lamp, and this he hung on a bar near to where he worked. By about 1 p.m. he had filled out his stint, and the deputy asked him to give a hand to Slater, the man below him: he stayed with Slater until about 2.30 p.m. Meanwhile (at about 1.45 p.m.) the cutter men (F. Roddy and L. Cadywould) arrived, and Smith helped them to get the trailing cable along the face up to the machine. Some 15 minutes later when Smith from his position down the face was looking towards the top, end he saw a flash and heard a crack from the machine which appeared to come from near the pommel end.
Shortly afterwards Roddy came down the face and as he passed Smith the latter asked what was the matter, to which Roddy replied, “The machine has burst.” After being away some little time Roddy returned, and in answer to Smith’s inquiry as to what he was going to do said, “Try it again.” A similar conversation took place between Walter Frost, another man in the face, and Roddy.
Confirmation of this occurrence at the machine was also given by Frank Mansell, one of the three contractors normally engaged in driving No. 9’s main gate scouring, but who on the day of the accident had been working at the roll. According to this witness Roddy and Cadywould arrived at the face about 1.30 p.m. and the contractors helped them to get the cable along the face. Cadywould later returned and asked the contractors to leave a shovel for him when they went out. This they forgot to do, but when dressing in 9’s scouring just after 2.30 p.m. Cadywould came to them again to get the shovel.
Before he left Cadywould said, “We have had a blue flame flash out of the side of the cutter,” and Mansell told him to tell Roddy to leave the cutter alone until someone had attended to it. W. Hardwick, a fitter, who also heard the remark, told Cadywould to get an electrician to the machine before working it again. There was, in fact, an electrician at the sub-station less than 300 yards away. Cadywould made no reply, but left with the shovel.
Herbert Smith having finished his work went to the tail gate (where his clothes were), dressed and proceeded outbye by that gate: he arrived at the pit bottom without knowing of the explosion, which must have occurred not more than ten minutes after he left the face. When he passed through the sheets in the tail gate they were in order, and he said he left them undisturbed.
Whilst working in his stint Smith had noticed a “Ringrose” detector hanging over the belt race towards the top corner, and this did not come into action during the shift nor did anything occur to suggest any abnormality in the ventilation. The detector was in charge of Edmund Smith who worked in the top stint, but, according to Herbert Smith, Edmund Smith, at about 2.15 p.m., went down the bank to give a hand between Slater and Cauldwell, six to eight yards below the tail gate. Edmund Smith did not take his clothes with him, but whether he took his “Ringrose,” Herbert was unable to state.
The coal-cutter men, as we have seen, reached the face about 1.30 p.m. When they descended at 1 p.m. they were seen at the pit bottom by the overman Brown who, learning that the second man (A. Pitchford) of the team of three usually with the machine had not turned up and that in consequence they had no “Ringrose” with them, told Roddy to use the “Ringrose” already at the face in the charge of E. Smith until a third man (Charles Moreton) who would be sent to join them arrived with another “Ringrose” detector. It should be here noted that no flame safety lamp was taken into the face by the cutter men, although it was stated at the inquest that the practice was for the coal-cutter team to take a “Ringrose” detector and a flame safety lamp with them.
Moreton went inbye with Sydney Smith, the gummer for the right bank cutter; they travelled in together up No. 6’s main gate and into 2’s right hand tail gate, and undressed about 200 yards from the face. Moreton then had a “Ringrose” detector and when he left Smith to proceed to the face (whence he would go up to the left bank) he was carrying this. For some reason, however, this detector never arrived in the left bank; it was, in fact, taken out after the explosion by Walter Bray (a stallman who worked in the winning heading at the extreme right of the face), who found it hung on a bar at the face almost opposite the right tail gate.
Moreton was found dead near the machine along with the two cutter men he had gone to assist; he could not have been in the vicinity of the machine more than a few minutes when the explosion happened.
Narrative Of The Explosion And Rescue Operations
Walter Frost who had been working just above the roll in the left bank had finished work, and at about 2.40 p.m. was putting his clothes on alongside the conveyor about 17 yards above the loader gate when there was a “crack like a shot out of a gun” accompanied by “a blue flame surging round my neck, my face and my legs,” then a cloud of smoke, and he was knocked over. He was severely burned, but crawled down the face to the gate end, then over the loader end and down the main gate as best he could, he being in the dark, and was found by men from the right bank who assisted him outbye; having received attention he was then taken out on a stretcher and sent to hospital.
The flame, said Frost, appeared to come down the face from the top end where the coal-cutter was. Frost carried an oil lamp.
Fred Bassett had also finished work and was in the loader gate facing the coal when there was a bang and a rush of hot air by which he was burned on the left side, neck and arm; the rush came from the left bank.
Of the persons still living these two were the nearest to the scene of the explosion at the time of its occurrence; they were both able to give evidence at the Inquest.
As already stated, the deputy, Willis Fish, was in the right bank 35 to 40 yards below the loader gate, when he felt the rush of air come from the left side followed by dust and heat. As a number of men were working in that bank he at once took them out by the right tail gate and up No. 6’s main gate on to the main plane, after which he proceeded up the loader gate to the face again, where he joined the shot-firer, John Dowds. On the main plane he met R. Warner, an afternoon deputy from an adjoining district, who told him he had already telephoned to notify the manager.
The shot-firer, as we have seen, was about 25 yards down the right bank at the time of the explosion. Accompanied by others Dowds returned to the loader gate, where he saw an oil lamp still burning, and then assisted in rendering first aid to Frost and Bassett. Just beyond the roll Baggaley was found alive partly buried under a fall and was removed and sent out on a stretcher, and close to him was the body of Furniss.
After setting some temporary supports in place of those which had been blown out, and turning on the compressed air to assist the ventilation, another body was found a little farther up the bank. By this time the first Rescue Brigade had arrived at the face.
In the bank near the deceased men the shot-firer noticed two extinguished flame safety lamps.
Brown, the overman, had left the pit, but on arrival home was informed by telephone of the explosion and immediately returned and proceeded below ground and met Mr. Limb (manager) on the main plane near to No. 7’s main gate.
Together they went up 7’s main gate and along 2’s left tail gate to within six yards of 7’s right hand airway where they encountered afterdamp and retreated. Going then up the loader gate they found two stretcher cases being treated, and proceeding up the left bank joined Dowds, Warner and others just before the arrival of the Rescue Brigade.
The Chesterfield Rescue Station received a call at 3.21 p.m. which was immediately answered and by 4.20 p.m. the first team had reached the coal face in No. 2’s loader gate. Proceeding up the left bank in advance of those already there they found two more bodies about ten yards beyond the others. This team got as far as the tail gate, but as practically all the timber in the bank had been knocked out and the roof showed signs of breaking they deemed it wise to withdraw for a consultation in the loader gate. At this stage they were joined by Mr. G. L. Brown (Manager of the Rescue Stations) and the Mansfield Brigade, who had arrived at the colliery shortly after the Chesterfield Brigade.
The three cutter men were still missing, and as they were believed to be near the machine in the top corner it was decided to approach the face by the left tail gate. At No. 7’s right hand airway carbon monoxide and firedamp were encountered, and in the tail gate, between 9’s left hand airway and 9’s main slit, a prop (with some brattice cloth attached) was found on lire and extinguished.
The Mansfield team was sent in to travel to the top corner of 2’s left bank by 9’s face, but were unable to do so owing to a large fall over which air was passing but which it was not possible for men wearing apparatus to get over.
Mr. Brown and the Superintendent then travelled the tail gate alone right to the face, and going up into the top corner the latter found the bodies of the remaining three men lying together close to the face at the back end of the cutter. Near them lay three electric lamps, two still alight and the other unlit. No flame safety lamp was found near this place, nor was there a “Ringrose” detector in the vicinity.
The “Ringrose” detector taken in by E. Smith — whose body was found ten yards above the roll — had been found lying close to the face opposite, but slightly on the low side of, the tail gate.
Mr. J. Hall, Senior Inspector of Mines, having been advised of the explosion, proceeded to the colliery at once and going below ground reached the fresh air base in the No. 2’s airway at 6.10 p.m. where he met Mr. John Hunter, the General Manager. Together they proceeded up the tail gate to the face and arrived just after the bodies of the three cutter men had been removed. A sample of the air taken eight feet from the machine (lower down the bank) showed just under one per cent. of firedamp, but the top corner was foul and over the machine there was an explosive mixture. Returning to the tail gate he found an explosive mixture of firedamp at the ripping lip, to a depth of three feet from the roof. There was a good current of air (augmented by a jet of compressed air from a pipe in the loader gate) passing along the left bank, but as most of it was going down the tail gate (the hurdle sheets having been blown down) instructions were given by Mr. Hunter to erect a brattice to direct it into the top corner.
Mr. Hall travelled down the left bank, and then through the Tight bank — which was found in good order — and returned by the right tail gate.
I arrived at the colliery about 8 p.m. and there found Mr. F. H. Wynne (H.M. Deputy Chief Inspector) who had come from the Company’s Warsop Main Colliery where, as a member of the Committee on the Firedamp Detector Regulations, he had been underground the same afternoon with other members of the Committee.
Shortly after my arrival Mr. Hunter and Mr. Hall returned to the surface and the position was discussed and arrangements made for further investigation. Accompanied by Mr. Hunter, Mr. Limb (Manager), Mr. Cowan (Junior Electrical Inspector) and Mr. H. Hicken (Secretary to the Derbyshire Miners’ Association) I later made an inspection of No. 2 left bank. Firedamp was still present over the coal-cutter, and, running obliquely across the bank from over the machine in the top corner to the face near the tail gate, an open break in the roof was showing from which firedamp was issuing.
On the morning of the 23rd January I again visited the colliery and along with Mr. Hunter, Mr. Limb and Mr. Hicken inspected the whole of No. 9’s face, the fall which, together with the presence of gas, prevented our doing so on the night of the explosion, having been. cleared to make a road through and timber having been erected to secure the roof from which the supports were blown out by the explosion.
Only a superficial examination of the coal-cutter by Mr. Cowan was possible on the night of the explosion, but it was noticed that the switch was in the “off” position. Later the machine and the trailing cable were brought to the surface for detailed inspection and test.
Cause Of The Explosion
The evidence of the survivors and of men working in the right bank, and the position of and injuries sustained by the deceased men (several of whom apparently had moved nearer the loader gate after the explosion), all clearly established that the explosion originated in the left bank and travelled towards the loader gate, the flame extending as far as the roll crossing that face.
Evidence of violence in the bank shown by displaced roof supports, articles of clothing, lamps, etc. indicated the point of origin as being near the top corner. Throughout the length of 9’s face roof supports were blown, out or displaced at various points, and there was slight coking on two or three props between 2’s face and 9’s main slit. In the left tail gate the hurdle sheets at the ripping lip were blown down, and between 9’s main slit and 9’s left hand airway some roof bars were displaced and a prop was found on fire as already explained. The direction of force in these cases, too, was from No. 2’s face.
It was therefore generally agreed that the explosion began in the top corner of 2’s left bank, and radiated there from down 2’s face and along 9’s face and, to a lesser degree, along the left tail gate. It was an explosion of firedamp, and in my opinion coal dust played little part in it. Two samples of dust taken on 9’s face after the explosion showed just over 50 per cent. of combustible matter present, and samples taken on the tail gate contained less than 30 per cent. of combustible matter. Limestone dust was used on the roads.
The nine electric lamps and four flame safety lamps issued to the deceased men and to Walter Frost were recovered and sent to the Mines Department Testing Station, Sheffield, where they were examined for defects likely to make them unsafe for use in the presence of firedamp. No defect in any of these was discovered to which an ignition of firedamp and air could be attributed.
Two flame safety lamps taken from the lamp cabin by two of the deceased stall men were unaccounted for, and a prolonged search was made for them on the face and in the wastes. They were later found extinguished about 150 yards from the pit bottom beside clothes belonging to these men, and had never reached the workings.
The “Ringrose” detector issued to E. Smith and later found on the face opposite the left tail gate about twenty yards from the coal-cutter was also examined by Capt. C. B. Platt in the presence of representatives of the Colliery Company and of International Gas Detectors Ltd., the makers of this appliance. It was fitted with a relay and was similar to that approved under the Firedamp Detectors (No. 2) Order, 1935, so that if the red bulb came into action it would remain glowing until turned off. A diagram showing the action of this appliance is given in Figure 2.
Externally it was found to be in good condition, but the carrying hook was bent out of shape suggesting that the detector had been wrenched from its support with some violence.
Further examination showed that the filament of the red bulb was intact and that the relay was in working order; furthermore, the heater filament was ruptured and the diaphragm bent in such a manner that the electrical contact attached to it was no long co-axial with its corresponding fixed contact.
A microscopical examination of the heater filament showed that it had been fused; the appearance of the fused ends is shown enlarged in Figure 1, from which it will be seen that one of the ends is of globular formation.
In Capt. Platt’s view the distortion of the diaphragm and the fusing of the filament in no way caused the apparatus to be capable of igniting an external mixture of firedamp and air, and there was no ground for thinking that the detector was in any but a safe condition up to the time of the explosion. He had little doubt that the distortion of the diaphragm was due to the pressure of the explosion, which would cause it forcibly to contract, and considerable strain of the diaphragm and its associated contacts would result. An experiment carried out with a new detector confirmed this view.
He attributed the fusing of the filament to the presence of a high concentration of firedamp in which the detector had been burning: experiments he carried out showed that 20 per cent. of firedamp or over is required to fuse the filament in a short time (approximately two minutes), but it might be less than 20 per cent, if the filament were glowing in the mixture for a sufficient length of time.
From this evidence I deduce that (1) the “Ringrose” detector was present in a rich mixture of firedamp and (2) it was not the cause of the ignition.
The coal-cutter, which was in the top end of the face, was working between 1.40 p.m. and the time of the explosion, and had cut a little into the rib side in the process of being turned round ready for starting to cut the face.
Shortly after 2p.m. something happened at the machine causing a visible flash following which the machineman went down to the gate-end switch box for some purpose — probably to replace the switch there — stating as he returned that he intended to “try it again”. What was done after this can only be surmised. It is reasonable to assume that either in switching on again or, if the machine was running — probably light as they were getting ready to re-set the anchor prop — in switching off, there was another flash, and this ignited an explosive mixture of firedamp and air surrounding the machine.
The switch was found in the “off” position, and Mr. Allott (Assistant Electrical Engineer) said he later found that in the reverse position it was definitely slow which would have the effect of extending the arc when switching off.
The machine was subjected to a minute examination at the surface by Mr. J. A. B. Horsley and Mr. J. Cowan (Electrical and Junior Electrical Inspectors) in the presence of Prof. I. C. F. Statham (for the Colliery Company) and colliery officials.
At the top flange of the door or cover enclosing the controller compartment there was no measurable gap, and the two side flange gaps could not be measured because of the design. In the bottom flange a feeler of .006 inch could be inserted, but the skid-plate on this type of machine prevented the insertion of a larger feeler and it was therefore not possible to measure this gap properly.
When the cover was carefully removed it was observed that coal and dirt had been trapped in the bottom right corner of the controller casing flange, causing a gap of inch in the flange joint. It was then decided to send the machine to the Mines Department Testing Station at Buxton for test as to whether in that condition it would pass flame, the flange gap being recreated by the insertion of 3/16 inch steel packing.
A preliminary observation test with a nine per cent. firedamp mixture inside the switch was first made, and flame was ejected through the gap at the cover joint. The test was then repeated. in an explosive mixture of 10.2 per cent. firedamp surrounding the machine, upon which external ignition resulted.
A further test under similar conditions was carried out with the metal spacer removed from the cover joint and the cover rebolted up tightly, and no ignition of the external explosive atmosphere occurred.
Plan 3 shows the cover plate and the situation of the dirt.
The presence of this coal and dirt has now to be explained. Two days before the explosion Alfred Thomas Harvey, one of the colliery electricians, visited No. 2’s face and examined the coal-cutter in question, which was then a few yards below the loader gate. He took the door off the switch compartment and examined the switch. The gun carriage was found to be loose, one screw having fallen out, but this was replaced, the other studs tightened, the contacts cleaned and all put in order.
In evidence Harvey said that before replacing the door he cleaned the facings with a piece of rag, and after puffing the door on tightened up the studs securely. He tried the top flange with his feelers, but tried the bottom only by running his fingers round, and was satisfied the door was in order. After this attention the machine cut through to the top end of the face and, this face not being at work on the following day, it remained there untouched until the arrival of the cutter men on the afternoon of the explosion.
Harvey again saw the coal-cutter on the Wednesday (the day before the explosion) and externally it appeared to be all right; the trailing cable and gate end switch gear were then examined and found in order.
It would seem that in replacing the controller door or cover plate, which is a fairly heavy casting, some coal and dirt lying on the floor was scraped up and trapped between the flanges at the bottom corner as afterwards found, and that by reason of its position and the inaccessibility of the bottom for minute examination the presence of this obstruction escaped detection.
It was unfortunate that, having seen the flash from the coalcutter shortly before the explosion and having therefore had warning of its unsafe condition, the men in charge of it decided to “try it again” instead of reporting the defect to the deputy or to an electrician. Had they so reported, the explosion might have been averted.
Presence of firedamp. — The presence of an accumulation of firedamp in the vicinity of the coal-cutter remains to be accounted for.
On both occasions on which deputy Fish visited the left bank during his shift he saw a roof break running diagonally from the face over the machine, and on the second visit at 1.35 p.m. it was a little more pronounced than at the first. As the coal was stripped out roof subsidence would naturally follow tending to open the break, and that this process continued was evidenced by the fact that after the explosion it was found to be much worse, and firedamp was then issuing from it and continued to do so for some time.
In his inspection after the explosion Mr. Hall also found an explosive mixture at the tail gate ripping lip, and an accumulation was present along the inbye end of 9’s face. A sample taken on the following day along this face where the roof was broken seven yards from the machine, and behind a brattice sheet erected to clear the top corner, gave over 58 per cent. of firedamp, and in the air current a little outbye of this there was 2½ per cent.
On the morning of the 23rd January, in a roof cavity extending from the face into the waste at the point (some 30 yards from the machine) where the main fall occurred to which reference has already been made, there was still an explosive mixture, and there was evidence of breaks extending over the gob and packs between 9’s face and the tail gate.
At what time the large fall occurred which was found on 9’s face after the explosion was not definitely established. It was not there at 10.30 a.m., and at 1.35 p.m. the deputy noticed nothing to indicate that any change had taken place. The appearance of the fall suggested that it occurred before and not after the explosion, but in any event there must have been a clear passage from 2’s face along 9’s face at the time of the explosion, and the fact that neither the deputy, nor Herbert Smith (who was working near the top end) nor anyone else noticed any change in the ventilation during the shift seems to indicate that the fall did not materially alter the course of the air current.
In my opinion the fall in conjunction with the break in the top corner is evidence that weighting of the roof was taking place in the area between the tail gate and 9’s face, accompanied by an abnormal emission of gas which the air current was not sufficient to deal with, and this in all probability developed between the deputy’s last visit and the time of the explosion.
Mr. Hall in evidence gave it as his opinion that rather too much of the air travelling up the left bank was getting away down the tail gate over the hurdle sheets (the area over the top of which was given as about nine and a half sq. feet), and while I think (as the officials suggested) that it was necessary and important to course sufficient air over the sheets to keep the gate lip clear, it was still more important to ensure that a good current of air swept the top corner where of all points on the face gas was most likely to collect and in which corner the coal-cutter had to operate.
Mr. Hall also expressed the view that the passage of the roll across the lower end of the left bank restricting the height by 1½ to 2 feet at that point would most probably have the effect of allowing more air to pass down the right bank than normally was the case, which seems to me a reasonable assumption
These circumstances in combination provide a sufficient reason for the accumulation in the top corner of the face.
I think it necessary to make some further observations in regard to two or three matters arising out of this accident.
(1) Electrical Apparatus at the Coal Face.
General Regulation 132 requires that in any part of a mine in which inflammable gas, although not normally present, is likely to occur in quantity sufficient to be indicative of danger, all cables and apparatus shall be constructed, installed, protected, worked and maintained, so that in the normal working thereof there shall be no risk of open sparking. The use of certified flameproof apparatus is not legally required even in safety lamp mines, and this is one of the matters under consideration by the Royal Commission on Safety in Coal Mines. But the question of maintenance is of equal importance. Obviously there can be little value in having any apparatus approved as safe for use unless it is kept in the condition under which the official test showed it to be safe.
In this case the coal-cutter, though ten years old and not of certified flameproof design, did, when tested in an explosive atmosphere with the cover properly closed, fail to ignite the surrounding mixture, but unfortunately the cover was not kept in this condition, partly owing to human failure and partly to the design, which did not permit of such careful gauging of the closeness of the joint as it ought to have had.
Even in machines of much newer design than that in question a similar difficulty is presented. In the manufacture of new machines this point should receive attention, and I suggest that the matter be brought to the notice of coal-cutter makers. It should also be possible, I think, to alter existing machines so as to ensure that after a cover has been taken off and replaced the closeness of the joints can be readily observed and tested in situ. H.M. Electrical Inspector of Mines is already considering means by which this may be effected.
(2) Firedamp Detectors.
The Coal Mines General Regulations (Firedamp Detectors), 1935, require that in every ventilating district in which safety lamps are required by the Act or regulations a sufficient number of firedamp detectors of an approved type (in longwall workings not less than one for every eight persons employed at the working faces) shall be provided for use by the workmen employed, and that each such detector shall be in charge of a workman who has been instructed in the method of using, and certified as competent to use, the type of detector provided.
Flame safety lamps and the “Ringrose” automatic firedamp detector have been officially approved by the Mines Department as detectors for the purpose of these regulations, and as already stated, both these types of detectors were in use at Markham Colliery.
The Staveley Coal & Iron Co., Ltd., indeed, were among the first to install the “Ringrose” automatic firedamp detector at their collieries, and since the year 1933 Mr. J. Hunter and his officials have by their investigations and suggestions contributed in no small measure to the improvement of this appliance to its present state of efficiency.
At the date of the explosion 133 “Ringrose” alarms or detectors were in use at Markham Colliery, and every man employed at the face had been instructed in the use of this appliance as well as how to test for gas with a safety lamp.
For each double-unit conveyor face four “Ringrose” detectors and a number of flame safety lamps were provided, two of the former for each bank (one at the end and the other a little distance from the centre gate) with the flame lamps spaced at intervals between these. The system (as explained at the inquest) was for each man appointed to carry a detector (of whatever type) to take it with him from the lamp cabin at the commencement and return it there at the end of the shift; in the event of any of these men being absent the detectors would be sent below ground to the deputy of the district for issue to other workmen.
Every encouragement was given to the workmen to make tests for firedamp and to watch the detectors carefully, the instructions being that if a detector indicated the presence of firedamp the men in the vicinity were to leave the face and report to the deputy at once. On several occasions the red bulb of a “Ringrose” detector has lighted up showing firedamp to be present and the instructions as to withdrawal have been observed; on arrival the deputy found gas present and having removed it the men returned to the face. The man who reported the gas was rewarded for his vigilance, and payment was also made to the workmen for any loss sustained through their withdrawal.
In view of these special precautions, and the attention given to safety matters in general at this colliery by Safety Committees and Safety Officers and the establishment of Fire Stations below ground, the officials naturally considered the possibility of an explosion as extremely remote.
Unfortunately it is not possible to state exactly where the “Ringrose” detector at the top end was hanging at the time of this explosion, but since it was found opposite the tail gate it must have been hanging somewhere between there and the top corner. It was in an explosive atmosphere and in view of its condition when tested appears to have functioned properly, but at what time it gave warning could not be determined.
It may be, as suggested by Mr. Hunter, that the cutter men switched off because they saw the red bulb, glowing; on the other hand, it is not unlikely that, being intent on their work, they failed to notice the detector, especially if it was some distance from them and on the gob side. It should also be noted that the diaphragm masks the red bulb over an angle of nearly 90 degrees, so that from certain angles the warning light may not be easily visible.
The fact remains, however, that there was a hitch in the effective provision and use of the detectors, and that full advantage was not taken of the efforts of the management to provide the best means available for the detection of firedamp as a safeguard against such happenings as this. Even a perfect detector will be of no avail if it is not used, and its warnings promptly acted upon.
This consideration raises the question as to the best position for a detector. Apparently it was customary here for the detector to be placed ahead of the machine somewhere near the anchor prop and moved forward with that prop from time to time, and I understand this is also the practice at other collieries.
In some conditions this may be a satisfactory arrangement, but where as in this case the machine is to cut downhill against the ventilation, I consider the detector should be kept as near the machine as possible if it is to serve the purpose for which it is intended.
Incidentally, the “Ringrose” detectors here were set to operate at two per cent. of firedamp. At this setting the detector does not meet the requirements of General Regulation 132 (v), nor provide the means for compliance with Section 60 (2) of the Coal Mines Act, 1911; to do so it must be set to function at 1¼ per cent., failing which a flame safety lamp must also be provided.
A further point arises. So long as a firedamp detector, whether automatic or flame lamp, is in the nature of a separate appliance additional to the lamp a workman needs to provide light for his work, it is liable to be regarded as an “extra” and treated accordingly, and excellent though the detector may be its object may be defeated by human neglect or failure. A man should always have his detector with him.
It would, in my opinion, be a distinct step forward if a lamp could be designed which combined a good light and an automatic detector in one unit, so that attention to the presence of firedamp would necessarily be directed by a diminution of the light.
I would like to express my thanks to Dr. McCrea, and to the colliery officials and the workmen’s representatives for their assistance in the investigations.
I have the honour to be,
Your obedient Servant,
J. R. Felton.
List of Persons Killed
|Name||Age||Occupation||Injuries||Cause of Death|
|Ralph Marsden||41||Stallman||Extensive burns over practically whole body.||Carbon monoxide poisoning.|
|Edward Baggaley||34||Stallman||Extensive burns over practically whole body.||Carbon monoxide poisoning.|
|Charles Moreton||29||Cutterman||Extensive burns over practically whole body.||Carbon monoxide poisoning.|
|Frank Roddy||25||Cutterman||Extensive burns over practically whole body.||Carbon monoxide poisoning.|
|Leonard Cadywould||21||Cutterman||Extensive burns over practically whole body.||Carbon monoxide poisoning.|
|Joseph Furniss||28||Stallman||Legs, arms, chest and back burned. Forehead lacerated.||Carbon monoxide poisoning.|
|William Caulwell||48||Stallman||Legs, chest and back burned. Skull and ribs fractured.||Carbon monoxide poisoning.|
|Edmund Smith||29||Stallman||Face, chest and arms burned. Scalp lace rated.||Carbon monoxide poisoning.|
|Wilfred E. Slater||30||Stallman||Face, arms and abdomen burned. Leg and ribs fractured.||Carbon monoxide poisoning.|