Polmaise 3 February 1934
Mine Tragedy – Three Men Killed in Fallin Pit Explosion – Injured Man's Action - Three men were killed and one man was seriously injured in a gas explosion on Saturday at No. 4 pit, Fallin Colliery, Stirling, belonging to Archibald Russell (Ltd.)
The victims were:-
William Quinn (31)colliery fireman, 20 The Square, Throsk;
John Samson (21),mine worker, 12 Fallin Rows, Fallin; and
George Forbes, mine worker, 13 Bruce Street, Bannockburn.
The injured man is Leslie Stewart (36), 42 Fallin Rows, Fallin, who lies in Stirling Royal Infirmary. Leslie was the hero of the disaster, haning crawled on hands and knees for fully a mile to warn the other workers what had happened.
The four men were engaged in dismantling an old place in the Hartley, section of the pit when the explosion occurred. There were actually 60 men at work in the pit, but they were in no danger, the explosion having occurred some distance away from the pit bottom. As soon as word was received at the surface that something serious had occurred underground, Mr James M'Donald, manager, and Mr James M'Kinlay, under manager, along with a rescue party, immediately descended the mine, and a few moments later Dr King, Fallin, arrived on the scene and was able to render first-aid to Stewart, who was in an exhausted condition after his ordeal in crawling along the mine road.
The bodies of his comrades were recovered at intervals of 15 minutes, and distressing scenes were witnessed when relatives arrived to identify them. The rescue party experienced considerable difficulty in removing the bodies of the three men from the affected section, which is in a remote part of the workings, a mile distant from the pit bottom. Before the victims could be reached a mass of loose material dislodged by the explosion, which was heard fully a mile away, had to be cleared.
One of the rescue brigade described the recovery of the bodies to a representative of The Scotsman. "We did not require to don gas masks to enter the section where the accident had taken place," he said. " Quinn was still breathing when we arrived, but he died as he was being carried to the pit bottom. The others had been killed instantaneously." Only the fact that an empty hutch lay between him and the seat of the explosion saved Stewart (the injured man) from the same fate. The three victims must have been thrown down with terrific force when the blast swept along the tunnel, for they were badly mutilated and burned." Quinn qualified for his under manager's certificate two years ago, and was studying for his first-class certificate. Two uncles of Quinn were killed in colliery accidents, one at Uddingston and the other at Burnbank, while his father dropped dead at the Fallin Colliery three years ago. Samson's younger brother lost his foot at the colliery last week. He was delivering a meal to his father when his foot was caught in the creeper, and it was found necessary to amputate it at the Stirling Infirmary. Mrs Stewart, wife of the injured man, told a reporter that she had a premonition of tragedy the night previously. After her husband had left for work she dreamt that site heard her daughter, who died about six months ago, saying several times, "Oh, mummy." “I am not superstitious," Mrs Stewart said, " but I was afraid there was something terrible going to happen." The manager of the colliery, along with Mr William Watson, the general manager, Glasgow, conducted an examination of the working place on Saturday afternoon to ascertain the cause of the explosion. Their official report is expected to be issued to-day. [Scotsman 5 February 1934]
EXPLOSION AT POLMAISE NOS. 3 AND 4 COLLIERY, STIRLINGSHIRE
122, George Street,
ERNEST BROWN, ESQ., M.C., M.P., Secretary for Mines.
In accordance with instructions I have the honour to make the following Special Report on the explosion which occurred at Polmaise Nos. 3 and 4 Colliery, near Stirling, on 3rd February, 1934.
Three men were killed, and a fourth was burned, but subsequently recovered.
PROCEEDINGS AT THE FATAL ACCIDENT INQUIRY.
Mr. John Dean Leslie, Sheriff-Substitute of Stirling, Dumbarton, and Clackmannan, conducted an Inquiry under the Fatal Accidents and Sudden Deaths Inquiry (Scotland) Act, 1906, on 23rd March, 1934, into the circumstances attending the three deaths.
Mr. Charles C. Cheyne, Procurator-Fiscal, led the proof for the Crown, and the following representatives appeared:-
Mr. J. L. Clyde, Advocate, for the Owners of the Colliery, Messrs. Archibald Russell, Limited,
Mr. Thomas Cassells, Solicitor, for the dependants of the two deceased workmen,
Mr. Andrew McAlpine, General Secretary of the Scottish Colliery Deputies' and Shot-firers' Association, for the relatives of the deceased fireman,
Mr. James Barbour, for the Stirlingshire Miners' County Union,
Mr. H. T. Foster, H.M. Senior Inspector of Mines, and myself, for the Mines Department.
The learned Sheriff-Substitute allowed all representatives ample opportunity to examine the 17 witnesses, 14 of whom were called by the Procurator-Fiscal and the other three by Mr. Clyde.
The verdict of the Jury was that an explosion of gas took place in No. 2 level, Hartley Coal Seam, in No. 4 Pit, Polmaise Colliery, and that the three men were so severely injured thereby that they died in the pit. The members of the Jury further unanimously agreed that it had been proved that the management's supervision over the air doors and the fan switch box was insufficient.
Two seams were worked in the mine, but as the explosion only affected the No. 3 section in the Hartley Seam, that section only will be considered.
As shown in Plan I [unfortunately this plan is missing from the copy of the report we transcribed], No. 3 section was approached by a main haulage dook, which was also the intake airway, dipping from the shafts at a gradient of 1 in 5. At approximately half a mile from the shafts two levels, Nos. 2 and 3, turned to the right out of the dook. The top level, the one nearer to the shafts, was No. 2 level and formed the top road and intake airway to the face of No. 3 section.
The bottom level, No. 3, was the return airway and haulage road from the face. In it was a small electric haulage.
Connecting the two levels were two headings, Nos. 3 and 4, which were still in service, No. 3 for a cable road from the bottom level to the top level and No. 4 as a self-acting jig road. Nos. 1 and 2 headings were stowed up.
Out of the bottom level, just inbye of No. 3 heading, a slope dip-road led to a small pump in a partly developed section which was stopped in July, 1933.
No. 3 section face was cut by an electric coal-cutter and the coal was filled into a conveyor delivering into the bottom level. When the section had advanced about 550 yards from the dook, the face struck a large downthrow fault and was cut off. Coal production ceased on 24th January, 1934, and withdrawal of material commenced. At the time of the accident all material had been recovered in the top level as far back as No. 3 heading and most of the material was out in the bottom level to the same heading.
When the section was being worked, ventilation was coursed in a descensional direction by means of two electric auxiliary fans, 20 inches and 15 inches diameter, situate just inbye of No. 3 heading in the top level. Sometimes both fans ran at the same time, but sometimes one or the other was used by itself.
There was a single door in the haulage dook to separate the intake from the return air, another in No. 3 heading and a screen cloth in No. 4 heading for the same purpose.
Three-phase current at 500 volts was carried inbye to the two fans by way of the return airway, where there was a switch at a place known as Gemmell's Dook Pump, to No. 3 heading, the cable making a loop into the bottom of the main dook to a bank of switches on its way. At the foot of No. 3 heading there was a switch and there was another at the top of No. 4 heading to control the smaller fan. There had been two switches there but one had been removed the day before the explosion, as will be explained later.
Thus, in the electrical circuit, from the pit bottom to the smaller fan at the top level of the section there were four switches in series, all of which required to be "on" before the fan motor could revolve. The question whether all the switches were " on " at the time of the explosion was an important feature in the investigations and Inquiry following the accident and is dealt with on p. 15.
The seam, being liable to give off firedamp freely, was worked with safety lamps, i.e., electric hand lamps and cap-lamps and flame safety lamps.
EVENTS PRIOR TO THE EXPLOSION.
As the section was not being worked actively the fans were not kept going continuously and generally stood from the time the day-shift fireman left until the night-shift fireman reached them.
On Wednesday night, 31st January, the night-shift fireman, Robert Wood, found the fans standing when he arrived in the section but there was no firedamp in the vicinity of them. He found firedamp in the bottom level between No. 3 and No. 4 heading but after he had run the larger fan for an hour or an hour and a half it had dispersed. He kept the fan running and saw no more firedamp during the shift. The smaller fan was out of order at that time, the key connecting the fan impeller to the shafting having come out.
On the following night, Thursday, Wood started the larger fan without examining for firedamp beyond No. 3 heading in the bottom level because, as he said, he knew gas came out of the workings beyond No. 4 heading, implying thereby that the result of a test was a foregone conclusion, i.e., firedamp would be found when the fans had been standing. After the fan had been running for some time he made an examination of the face and found it closed by a fall between the bottom level and the dummy road above that level. This fall impeded the ventilation and he found firedamp, which he estimated at two per cent., in the bottom level at the foot of No. 4 heading. According to a statement he made to Mr. Foster it was a further half hour before the fan cleared the gas sufficiently for him to penetrate to the face of the bottom level. This statement leads me to suspect that the firedamp was present in far larger proportion than two per cent.
At 2 a.m. on Friday, 2nd February, Wood fenced off both the top and bottom levels by props placed just inbye of No. 4 heading. He then removed the brattice screen in that heading and short-circuited the ventilation. From that time until the explosion occurred, some 29 hours later, the section inbye of No. 4 heading was abandoned and unventilated.
During the day shift of Friday, an engineer, an electrician, and other men were busy dismantling and disconnecting machinery in the section. The large fan was dismantled and the switch removed but the small fan was repaired and left in running order. Owing, however, to the alteration in the ventilation made by Wood, there was no need to run either of the auxiliary fans, because the main ventilation of the pit was sufficient to provide for the small area of the section that was left.
On Friday night Wood, the fireman, did not attempt to run the small fan - not knowing that it had been repaired and could not work the larger one because it was dismantled, but found no need for either. The surface fan was providing sufficient ventilation to keep the top and bottom levels and No. 4 heading clear of firedamp, except that just outside the two fences inflammable gas could be detected, passing from the abandoned area into the general air current.
During his first inspection he found what he estimated to be 1 1/2 per cent, of firedamp at both places but, during his second inspection, the gas was slightly richer at the fence in the bottom level. When he arrived at the pit bottom shortly before 6 a.m. on Saturday, 3rd February, he informed the day-shift fireman, William Gerard Quinn (who was one of the victims of the explosion), of the state of the ventilation and as to the presence of firedamp. Then ensued this conversation :-
Quinn - "Did you try that wee fan?"
Wood - "No. It's broken down, surely? "
Quinn - "We sorted it yesterday."
Wood - "If I had known it was sorted, I'd have given it a run."
Quinn - "I'll give it a run to see if it is in order."
Wood - "All right."
NARRATIVE OF THE EXPLOSION.
After the above talk Quinn, acting on the instructions of Andrew Smith, oversman of the pit, collected three men, George M. Forbes, John Samson and Leslie Stewart, in order to continue with the work of recovering material from No. 3 section. They procured two bogies from the pit bottom and attached them to a train of tubs in the dook. Forbes stayed behind to operate the haulage motor whilst the other three men rode down in a train to the top level. Whilst waiting for Forbes to walk down, the men turned the bogies into the level, then Stewart and Samson fetched up a bogie with sides from the foot of the dook, which was near the bottom level.
Stewart was asked by the fireman, Quinn, to make sure that the switch for the fan was "on" and though Quinn did not state his reason for this request it conveyed to Stewart's mind that Quinn was going to run the remaining fan, since the switch controlled that piece of apparatus only. Stewart found the switch "on" and, after returning with the bogie, informed the fireman so. Stewart also noticed that the single door in the dook - between the top and bottom levels - was closed both when he went down and after he had returned through it. He had good reason for observing this door closely because he had been punished by the loss of a week's work on a previous occasion for leaving it open and causing the section to be "gassed out".
The men had some food until Forbes rejoined them and then they all set off along the top level. The fireman, Quinn, who was leading, had a flame safety lamp and an electric cap-lamp ; Samson, who followed next with a bogie, had an electric hand lamp; Forbes, who was third at some distance behind with a flat-bottomed bogie, had an electric hand lamp, and Stewart, who was last, pushing the bogie with sides, had an electric cap-lamp. Forbes had been supplied with a flame safety lamp but had left it in the main road near the pit bottom.
Forbes encountered, with his bogie, a stone projecting from the pack side and was delayed and Stewart caught up with him. A conversation between them about the stone was interrupted by the explosion. Stewart was blown off his feet and carried outwards. When he landed on the floor he "rolled like a ball", to use his own words. He heard a loud noise and felt a concussion and could feel that he was burnt. As he attempted to rise he saw the flame returning inbye near the roof and kept low until it had passed. His belt had burst and his cap-lamp had been torn away from him so he was then left in the dark and could feel hot particles, going in an inbye direction, still striking him. His cries to Forbes brought no response so he concluded that he was the only one left alive in the section. He made his way in the dark for over half a mile to the pit bottom. His shouts, heard at the pit bottom, were the first intimation to anyone that there had been an accident, but Stewart, though extremely shocked and exhausted, managed to say that an explosion had occurred.
A telephone message was sent to the Manager, Mr. James McDonald, on the surface, and within a few minutes he was below-ground. Hastily making arrangements for a rescue party to follow him he rushed down the main dook, past the top level to the bottom level - the return air road. There he found the air to be hazy and warm, and, as he had no flame lamp for testing purposes, he retired up to the top level where he was shortly afterwards joined by the ostler with a flame lamp. Again he ventured down to the bottom level and was able to penetrate a little way inside. Judging by the smell that no fire existed he then felt that rescue work might safely be attempted. He had taken particular notice that the switches in the main dook, including the one which Stewart had seen in the "on" position, were all "off".
By this time more assistance was available and the rescuers started along the top level. The first body found was that of Forbes, lying crushed between the bogie with sides, which had been turned round, and the left side of the road. Forbes had sustained a compound fracture of the skull, a nearly severed right arm, broken breast bone and fractured right leg. His face was burned and both arms were badly peppered with hot coke. It was obvious that he had been killed outright.
Sixty-five yards further inbye were the bodies of Samson and Quinn. Samson's face, both arms and back, were burnt and he was peppered slightly with coke. There were unmistakable signs - which were afterwards confirmed by a post-mortem examination - that death had been the result of carbon-monoxide poisoning.
Quinn, who was lying face downwards, was burned on the forehead and both arms but was otherwise unhurt. He died from carbon monoxide poisoning and there was some doubt at to whether he was actually dead when found or whether death occurred shortly afterwards.
The Manager, having seen to the removal of the bodies, advanced another 37 yards to the fan switch-box, which he opened and examined perfunctorily.
The bodies were conveyed out of the mine, everybody left the section, and H.M. Inspectors were notified.
RESULTS OF INSPECTION AFTER THE EXPLOSION.
Mr. H. T. Foster and I, accompanied by the General Mine Manager, Mr. James Watson, the Manager, Mr. MacDonald, the Manager of Cardowan Colliery, Mr. John Williamson, and others made an examination later in the day.
A search by the Police of the clothing of the dead men in the mortuary disclosed that none of them was carrying matches or smoking material.
In the top level of the section - see Plan II - an electric hand lamp was discovered close to the turned-round bogie where Forbes had been found. The well glass was broken and the bulb was missing. An overturned flat bogie was close to, but inbye of, the bogie with sides that Stewart had been pushing. The larger bogie had struck a roof bar and had partly displaced it. Here was evidence of force in an outward direction and corroboration of Stewart's statement.
The last traces of heat or flame were found on a broken bar ten yards inbye of where the body of Forbes was found. From the burns on the body and from Stewart's statement and burns, it was evident that flame had passed this place, yet it had left no visible trace.
Heavy coke deposits on the outbye side of steel arch girders were noted 40 yards further in for a few yards, but had practically disappeared at 65 yards from the position of Forbes' body. At that place, where Samson and Quinn had been found, was another electric hand lamp - Samson's - still burning and in safe order. Quinn's cap-lamp accumulator was found on his body, the lantern and cable 27 yards inbye and the cover of the accumulator case six yards further inbye, only eight feet from the switch of the fan.
An undamaged flame lamp - the fireman's - was found opposite the outbye corner of No. 3 heading and at this place the investigation party found an explosive mixture of firedamp and air near the roof.
The door in No. 3 heading was found partly open and could not be closed without clearing some loose rubbish from the floor. All the ventilation was short-circuiting to the bottom level down this heading through the open door. Beyond this heading the firedamp mixture in the top level became stronger and extinguished a lamp flame approximately at the fan switch.
Examination showed that the fan had been stationary when the explosion occurred. The driving belt was glazed by heat on the upper side but not on the under side. The fan itself was easily revolved by hand without undue effort and was seemingly in working order and was not seized or in a condition to cause sparking or undue heat.
The switch for the fan - see Figure 1 (a) and (b) - was "off," as it had been left by the Manager earlier in the day. A casual inspection disclosed that it was not flameproof. There was an annular aperture between the feeder cable and the cable gland through which a pencil could be passed. A similar, but larger, aperture existed where the supply cable entered. This piece of apparatus will be described later.
Beyond the fan was the bogie which Samson had been pushing; the carcase of the larger fan, which had fallen over on its side; and a broken door. The door had originally been placed there to prevent the air blown forward by the fans from returning but the explosion had broken it. Parts were found inbye and outbye of its usual position. There was a deposit of soot at this part of the top level.
Further than six feet inbye of the fan no visible traces of the explosion could be found, but examination of this length and beyond had to be postponed until the door in No. 3 heading had been closed and the mine ventilation had cleared the top level of firedamp, which it did as far as No. 4 heading in half an hour. The inspecting party found that firedamp was pouring through the fence in the top level and polluting the air current to the extent of three per cent., which later was reduced to two per cent., in a current of 3,000 cubic feet of air per minute. Outbye of No. 3 Heading in the bottom level there was only 1 1/2 per cent, of firedamp in the air current.
No attempt was made to penetrate through the fences in the top and bottom levels because the roads beyond were fouled with fieedamp, which was never removed.
The exploration party withdrew on Saturday evening on the promise of the General Mine Manager that nothing would be disturbed until a further examination could be made on Monday morning - a promise that was not carried out.
All the safety lamps used by the victims of the explosion were recovered and submitted to test at the Mines Department Testing Station.
After the fan motor and switch gear had been carefully examined underground by Mr. E. Crawford, H.M. Junior Electrical Inspector, on 5th February, they were brought to the surface and minutely examined there by Mr. J. A. B. Horsley, H.M. Electrical Inspector, on 8th February.
As the result of the underground inspection it was clear that the explosion had been one of firedamp, extended somewhat by coal dust: that it had been entirely confined to the top level of No. 3 section : that the visible signs of burning extended from two yards inbye of the fan to 92 yards outbye of it, but the flame had extended some yards further without leaving a trace : that the evidences of direction of force all pointed outbye: and that the least violence was found nearest to the fan and the most violence at a distance from the fan. From these data it was concluded that the origin of the explosion was near to the fan, which conclusion was supported by Stewart's statement that the explosion came from inbye towards him.
ORIGIN OF THE FIREDAMP.
Fireman Robert Wood stated that he had never found firedamp in the vicinity of the fans but he expected to find firedamp in the bottom level near the face after the fans had been standing a shift. He did, in fact, find it there. Wood also stated that on 21st January a feeder of firedamp was struck in the face on the low side of the bottom level. His evidence, that on the morning of the explosion inflammable gas was issuing through the fences in the top and bottom roads of the abandoned part of the section, indicated that the whole section beyond the fences was full of firedamp.
Add to this the experience of the members of the inspecting party who found that, with the door in No. 3 heading partly open, the top level was clear of firedamp as far as the heading but full of an explosive or extinctive mixture of firedamp and air beyond that heading, there should be no difficulty in deciding that the inflammable gas was given off from the inbye portion of the district.
The course taken by the flame of the explosion indicated that it extended outbye only, and this was because only in that direction was there air for combustion : inbye the firedamp was too rich to explode, so the flame died out in that direction. That two of the men died from carbon monoxide poisoning from such a small explosion demonstrates that there was a deficiency of oxygen and hence an excessive production of carbon monoxide gas.
However, at the Fatal Accident Inquiry, the theory was first advanced by the Manager and afterwards elaborated by Professor Daniel Burns, who formerly occupied the Chair of Mining at Glasgow University, that the firedamp came from troubled or faulty ground in the vicinity of the old gobbed-up No. 2 heading and that it was liberated by movement in the upper strata just at that particular time. The fact that the explosion left no signs beyond the fan was explained by supposing that the explosive mixture did not extend beyond No. 3 heading. The point of ignition was supposed to be at the top of No. 3 heading.
It is necessary to consider what this theory involves. Firstly it presumes that there was sudden movement in strata which had been quiescent for practically two years: that this movement occurred after the fireman Quinn had passed but before Forbes and Stewart reached the place: and that firedamp was emitted in such quantity that it made the atmosphere of the level explosive yet without any audible roof movement that could be heard by Stewart or that might have alarmed Quinn and Samson.
As the quantity of air passing the place under similar conditions was recorded in the ventilation book by the assistant manager on the previous day to be 3,200 cubic feet per minute - and this was subsequently confirmed by H.M. Inspectors - there must have been an emission of about 200 cubic feet of methane per minute to render the air current explosive - a quantity which was rather more than three times the normal amount liberated by the whole district - yet no trace of this large feeder was found by the rescue party an hour afterwards or by the investigation later in the day. No fall of ground, such as might be expected to accompany a heavy roof movement liberating a blower of firedamp, was found.
This theory was put forward to account for the explosion not having travelled much further inbye than the fan but, if there had been an explosive mixture extending from No. 2 heading to the supposed ignition point at No. 3 heading, the expansion upon ignition would have carried the flame a greater distance inbye than it was found to have gone, and it would probably have ignited the explosive mixture beyond the fence at the top of No. 4 heading.
A much more simple explanation was that the firedamp, which was known to fill the inbye part of the district up to No. 4 heading, where it was diluted by the air current, was enabled to creep out as far as No. 3 heading, owing to the door having been left open in this heading and consequent short-circuiting of the air.
There is no direct evidence that the door had been left open but it was found open after the explosion and could not be closed except by removing small stones from the floor. These stones wore not the result of any fall but merely ordinary floor dirt which might have been moved downhill into the path of the door by the explosion or might have been there previously.
If the door was left open it could only have been done so by Robert Wood, night-shift fireman, but he asserted that he had closed it and fastened it by means of a wire attached to a nail in the door. Neither the wire nor the nail were seen by anyone after the explosion, so there was no corroboration of his story.
When the door was found open after the explosion, air was short-circuiting down No. 3 heading and none was passing forward to No. 4 heading. Firedamp had filled the top level as far as No. 3 heading and could be found as an explosive mixture there, where it was partly diluted by the fringe of the air current going down the heading. When the door was closed the firedamp was driven back at a walking pace to No. 4 heading.
An experiment was tried by Mr. H. T. Foster on 8th February, when it might be expected that the evolution of firedamp from the abandoned workings would have become slightly less. He opened the door in the main dock between the entrances to the top and bottom levels and thus short-circuited almost the whole of the ventilation of the section, which he had found to be 3,456 cubic feet per minute. In three hours firedamp from the inbye part of the district had worked back to No. 3 heading and there was an explosive mixture close to the top of it at the fan switch-gear. One hour later the firedamp had extended 60 feet outbye of No. 3 heading in spite of a small quantity of ventilation which was leaking through the badly fitting door in No. 3 heading.
When the door in the main dook was closed, the ventilation resumed its proper course and effectively cleared away firedamp as far as No. 4 heading.
During this experiment, even with the ventilation of the section nearly stagnant, no firedamp was found in the vicinity of No. 2 heading, but some was found to be issuing from faulted ground between No. 3 and No. 4 heading before Mr. Foster was compelled to retreat owing to the advance of the gas from the face.
CAUSE OF IGNITION.
The process of elimination gave the following results :- All the safety lamps were submitted to test and were found to have been incapable of igniting explosive mixtures of firedamp and air, except the electric hand lamp carried by Forbes, which was found at the tail end of the explosion, obviously broken by the force of the explosion. The evidence of the survivor, Stewart, showed that this lamp was intact until the blast of the explosion reached it.
The only machinery in the level was the fan and this was not in motion at the time of ignition, so that sparks caused by machinery could not have lit the gas. As none of the men was using any tool, sparks from that source can be eliminated.
There were no signal or telephone circuits.
The only length of electric cable in the top level was a short length to the fan from No. 3 heading and this was found to be in good order. It had not short-circuited or otherwise caused any spark.
No falls of rock which might have caused frictional sparks had occurred. The roof material was of a soft nature.
From the evidence of Stewart no man was smoking. In the presence of the fireman it would hardly be credible. No smoking materials or matches were found in the men's clothes.
No short firing was in progress or contemplated.
There remained only the possibility of the ignition being of electrical origin. The fan motor was found to be in order, but the switch for the fan was obviously not flameproof and sparking inside it would be equivalent to open sparking.
The switch handle was found to be in the downward position and required to be lifted to start the fan, but the mechanism was loose and the handle would fall into the "off" position unless the switch blades were forced well home.
The switch consisted of a "Diamond" gate-end box mounted vertically upon a Harland Engineering Company's Tee box. A sketch of the interior of the switch box and the Tee box, made by Mr. Crawford, H.M. Junior Electrical Inspector, is shown in Figure 2.
The incoming cable armouring was secured to one of the glands of the Tee box and the cable itself, minus armouring and measuring 1 1/4 inches in diameter, passed through a hole 2 1/16 inches in diameter in the gland, leaving an open space of 2.11 square inches, only partly obstructed by the widely spaced wires of the armouring. The cable gland was originally designed for a much larger size of cable.
The Tee box was intended to be filled with compound but was not, so filled. As found, without compound and with no gasket round the lid, with clearances up to one eighth inch wide, between the lid and the thin cast edge of the carcase, the box was obviously not flameproof. As the Tee box communicated with the interior of the switch box by means of a hole 1 1/4 inches diameter, through which the four tails of the supply cable passed, any explosion in the switch box would be communicated to the Tee box.
The outgoing cable left the top of the switch box through a gland, also too large : the open space in this instance was 1.18 square inches.
This Diamond box of 100-ampere capacity, contained three air break switches and three renewable fuse carriers. Three slate panels each carried a pair of switch and fuse contacts for one phase.
The right slate panel was cracked through one of the screw holes of the bearing supporting the switch spindle, and consequently there was unintended movement between the lower switch contact and the upper one. This prevented the three blades on the spindle entering the contacts simultaneously on every occasion. By closing the switches slowly ten times Mr. Crawford found that the centre and left blades in six trials entered before the right one. He confirmed this test by "megger." The effect of this defect would be that if the switch were closed slowly, contact and sparking might occur at two of the blades before the third made contact and the fan motor would not be started.
The officials of the Company failed to obtain similar results when the switch was brought out to the surface of the mine, but it is quite possible that the broken slate panel was disturbed in position by vibration during transit.
The switch, which could be partially operated without starting the fan motor but yet sufficiently to permit internal sparking, seemed to provide the solution as to the cause of the ignition.
Add to this circumstantial evidence the statement of Quinn to Wood, that he intended to give the fan a run, and Quinn's action in sending Stewart to see if the fan switch was "on," and suspicion is strengthened greatly.
The position of the men adds more weight to the theory.
Samson was found 38 yards outbye of the switch and his position and injuries indicated that he had never moved after the explosion. He was lying on his back with his head pointing outbye as if he had been facing inbye at the moment he fell.
On the other hand, although Quinn was found at the same place, the cover of his lamp accumulator case was only eight feet from the fan switch: his cap was at the top of No. 3 heading about four yards from the switch : his flame lamp was seven yards from the switch : the lantern and cable of his cap-lamp were two yards farther outbye. It was evident that the explosion had caught him somewhere near the switch, where there had been no great violence. He was burnt and knocked down but managed to stagger or crawl out to Samson's body before he collapsed.
That Quinn had left his flame safety lamp on one side, and had gone forward to the fan without it, seems to indicate that he found firedamp and left the lamp behind whilst he advanced to start the fan in order to clear the gas.
The lamp was found at the exact place where the exploring party first encountered gas when the door in No. 3 heading was open, and helps to confirm the theory that the door was open before the explosion.
The bogie that Samson was pushing was found slightly inbye of the fan switch and yet Quinn started in advance of Samson. This appeared to point to either both men having arrived at the fan or else to Quinn having taken over the bogie and having gone ahead.
It was more probable that both men reached their destination and that Samson was sent back to keep the other men from too near until the gas had been cleared.
The case for the fan switch having caused the explosion seems overwhelming but at the Fatal Accident Inquiry Mr. Clyde brought out a considerable volume of evidence tending to show that there, was no electrical current at this switch at the time of the explosion.
Firstly, there was the Manager's evidence that when he led the rescue party, the switch at the foot of the main dook was “off." This was easily explained because the switch had a no-volt trip which had operated and opened the switch when the pump attendant at Gemmell's Dook pump had opened the switch nearer to the shaft bottom, before the Manager reached the main dook switch. The definite evidence of Stewart that he saw that the switch, which the Manager referred to, was "on" shortly before the explosion clears up the matter.
Secondly, the Manager's evidence was that the switch at the fan was "off" when he examined it during the rescue operations. The mechanism of the switch operated very easily and the weight of the handle would return the switch to the "off" position unless the knives were forced into the contacts. As it was clear that the fan had not been in motion the switch could not have been properly closed, but it was possible that the fireman Quinn was in the act of closing it when the explosion occurred and that he released the handle and it fell back. He may even have pulled the switch back during his instinctive withdrawal when he saw flames emerge from the switch. There was nothing inconsistent with the theory that the switch caused the explosion in the handle being found in the "off" position.
Thirdly, there was a switch at the foot of No. 3 heading in the bottom level, intermediate in the electric current between the two switches concerning which the Manager gave evidence.
This switch was not examined by H.M. Inspectors on the day of the accident. It was intended to make a more thorough examination on the following Monday and reliance was placed upon the promise that nothing would be disturbed in the meantime. However, during the intervening Sunday the Colliery electrician and others visited the section and interfered with the switch. The electrician declared that he found it in the "off" position and stated at the Inquiry that the handle was covered with dust and, therefore, no one had touched it since the explosion occurred. He knew perfectly well that the switch could not be opened by the handle and that it was necessary to depress a small trip lever on the other side of the switch to return the handle to the ''off" position, so there was no useful point in his evidence concerning the dust on the handle. He asserted that he had not examined the trip lever - the vital point - for signs of dust. His evidence was so peculiar that I attach no credence to it.
Mr. J. Watson, General Mine Manager, gave evidence to the effect that when he accompanied Mr. Foster and me on Saturday, the day of the explosion, he noticed that the handle of this switch was in the " off " position and pointed it out to the oversman, Andrew Smith. It was unfortunate I did not examine the switch then instead of relying upon the promise that nothing would be interfered with before the inspection on the following Monday, and it was also unfortunate that Mr. Watson did not point out his discovery to me, but his explanation was that he the thought the switch belonged to another circuit. The oversman was not called to corroborate Mr. Watson's evidence at the Inquiry, and never happened to allude to the incident when being question by HM. Inspectors prior to the Inquiry.
If Mr. Watson was not mistaken in his recollection or observation and it would be easy to mistake the position of this switch handle because was no marked difference between the "off" and "on" positions - the theory that the explosion had an electric origin is disposed of.
On the other hand, this switch was defective. It had been made with three overload trips and a no-volt trip, but the no-volt coil had burnt out about six months before the explosion and an apprentice electrician, having disconnected it, rigged up the switch so that it, worked without the automatic no-volt release. In consequence the switch remained closed when the one in the main dook was opened and was regarded by the firemen as of little account. It was generally left in the "on" position and reliance was placed upon the switch in the main dook, which was more handy. The electrician who disconnected the large fan from the circuit, on 2nd February did not open the switch at the bottom of No. 3 heading, but his knowledge of the section was limited and, without tracing out the cables, he may not have known that the switch was in the fan circuit.
The case is different with Quinn, who knew the section well. He instructed Stewart to see that the main dook switch was "on" but, gave no instructions regarding the intermediate switch in the bottom level. It seems strange that he should be going forward with the expressed intention of starting the fan some time during his shift, without assuring himself that the bottom level switch was "on," unless he knew from past experience that it would have been left "on" and that there was no need to waste time verifying it.
The night-shift fireman, Wood, when he was questioned on 6th February by H.M. Inspectors, who took written notes of his statements, said : "On Saturday morning (3rd February) when coming outbye on No. 3 level (the bottom level) I did not pay any attention to the switch at the bottom of No. 3 heading. As a rule I found this switch in the 'on' position and did not need to close it."
At the Fatal Accident Inquiry on 23rd March he said that he put the switch in on Thursday night for the purpose of running the fan and took the switch out again on the Friday morning.
In answer to Mr. Clyde he said he usually found it "off" and if he wanted to turn on the fan it was necessary to turn the switch " on."
Of these conflicting statements I think that the one made to H.M. Inspectors, when his memory was fresh, is the correct version and that it was not the custom to bother with the switch, which was left "on" permanently.
OTHER THEORIES AS TO THE CAUSE.
Although the colliery officials attempted to exonerate the fan switch as the cause of the explosion, the only other possible explanation they attempted to put forward was, in the words of Mr. Watson, "It might have been a lamp."
Professor Burns went further and definitely ascribed the explosion to the fireman's lamp. He stated that he enclosed a lamp similar to the flame lamp carried by the fireman, in an explosive mixture containing about 7.5 to eight per cent, of coal gas and operated the relighting mechanism. Once out of six times the mixture, ignited inside the lamp, caused the external mixture to be ignited.
The futility of testing a lamp in a mixture with air of coal gas containing hydrogen to ascertain its probable behaviour in a mixture of air and firedamp needs no comment.
The Testing Officer at the Mines Department Testing Station submitted the lamp used by fireman Quinn to the following test : - The lamp was suspended unlighted in the most explosive mixture of firedamp and air; after sufficient time had elapsed for the lamp to fill with the mixture an electric spark was passed within the lamp. The flame of the explosion within the lamp did not pass to the mixture surrounding it. The test was repeated ten times with the same result.
In view of these tests the flame safety lamp can be dismissed from consideration as a probable cause of the explosion.
Professor Burns thought that the theory that the fan switch had caused the explosion was an impossible one because he could find no sign on 21st March of an internal explosion on 3rd February and because the Manager, when he examined the switch during the rescue operations, did not notice signs of condensation inside.
In regard to the first of these arguments, hundreds of tests are made by H.M. Electrical Inspector on electrical apparatus submitted for the purpose of being certified as flame-proof. Firedamp mixtures are exploded inside and are usually found to leave no trace.
In regard to the second contention, the switch box was small and well ventilated through the cable glands. The volume of water remaining inside the box immediately after an explosion would be in the region of 0.003 cubic centimetre and this, distributed over the surface of the box, switch gear, fuses, etc., inside, would require a microscopical examination to detect.
The Manager's examination was admittedly cursory and made under conditions of stress; he did not notice the broken slate panel or the spaces between the cable and glands : he was not looking for condensed moisture : his examination was made almost two hours after the explosion, when it might be expected that any slight film of moisture would have dried oil.
If the Manager had noticed condensation on the outside of the switch - due to the external explosion - but none inside, it would have been evidence that the explosion did not start inside the switch. Yet neither he nor any other observer saw condensation on the outside of the switch or upon any of the arch girders in any part of the road where the flame passed.
These arguments against the fan switch and for the safety lamp as the origin of the explosion are certainly not convincing.
After weighing the matter carefully I have come to the following conclusions :-
(1) The ventilation of the section by the fan on the surface was adequate after fireman Wood had removed the brattice in No. 4 heading.
(2) The ventilation: became inadequate owing to the leaving open of a door in No. 3 heading, which resulted in firedamp, given off from the coal face of the section and, to a less degree, from the roadways inbye of No. 3 heading, accumulating and filling the top level as far outbye as that heading.
(3) The fringe of the accumulation consisted of an explosive mixture of firedamp and air, but the inbye portion was too rich in firedamp to explode or burn.
(4) The explosive outer edge of the firedamp accumulation was ignited by sparking inside the fan motor switch during an attempt to start the fan. The ensuing explosion extended slightly more than 100 yards in the top level and was confined to that level.
(5) The fan switch was not flameproof and, although it was placed in an intake airway where inflammable gas had never been reported and where it was only likely to occur as the result of some accident, it was not in keeping with the provision of safety lamps and other safeguards against gas adopted in this mine.
(6) The door in No. 3 heading was so fixed that it opened with the ventilation when provided by the fan on the surface but would tend to be closed by the ventilation produced by the auxiliary fans, when they were running. In these circumstances there should have been two doors in No. 3 heading, opening in opposite directions.
(7) In the main dook there was only one door between the intake and return levels. The risk of a single door being left open was one which ought not to have been incurred, especially after one example of the evil effects resulting had been provided when Stewart accidentally left the door open for a shift.
I have the honour to be,
Sir, Your obedient Servant,
E. H. FRAZER.