HAPTON VALLEY. Burnley, Lancashire. 22nd. March, 1962.
Hapton Valley Colliery was in the N.C.B. North West Division on the boundary of the County Borough of Burnley. The structure of management was Mr. R. Lowe, Area General Manager, Mr. J. Whittaker, Area Production Manager, Mr. W.E. Rawstron, Group Manager, Mr. A.L. Wier, Manager, and Mr. R. O’Hara, Undermanager.
On the day of the explosion, Mr. B. Kennedy, a certificated colliery manager was in charge of the colliery in the absence of Mr. Weir. The colliery, which employed three hundred and eighty-six men below ground and sixty-seven on the surface, had a daily output of about 700 tons of saleable coal all got from two faces Nos.2 and 5 in the Union Seam.
The colliery had three shafts. No.3 was the downcast shaft used for winding men coal and materials, No.4 was the upcast shaft used for winding men only and the No.2 shaft was used for pumping water. The No.4 shaft was equipped with an electrically driven exhausting fan producing 112,000 cubic feet of air per minute and 4.3 inches of water gauge.
Following the completion in January 1962 a surface drift, 1,260 yards long and dipping at a gradient of 1 in 4.16 was brought into use as a second intake. Before this drift connected with the mine workings the ventilation of the mine had been assisted by a booster fan situated in the main return airway about half a mile from the bottom of the upcast shaft. Because it no longer made a significant contribution to the ventilation of the mine, the booster fan was taken out of commission and put on care and maintenance basis in March 1962.
The colliery had always been a safety lamp mine and in addition to electric cap lamps in general use flame safety lamps were issued to officials and elected workmen as firedamp detectors. These lamps were of the internal re-lighter type.
The Union Seam was 171 yards deep at the shafts and the only one that was worked at the colliery and was from 3 feet 4 inches to 3 feet 9 inches thick with a hard fireclay floor and a roof of medium-strong shale. As a result of faulting, the cover at the face of No.2 District was 242 yards. The seam was gassy and in before this explosion, there had been three ignitions of firedamp at the colliery.
On the No.1 face, which was discontinued, there was an ignition during shotfiring on 23rd June 1960 and another in the undercut attributed to frictional sparking on 28th July 1960. The third ignition also ascribed to fictional sparking in the undercut occurred, in No.2 return gate stable on 4th April 1961.
To reduce the risk of ignition in the undercut, the management had installed cutting jibs with an internal water feed. The cutting machine on the main face line was also fitted with a compressed air/water ejector for ventilating the undercut, but this additional safeguard could not be applied to the machines that were undercutting in the stables.
The No.2 face was 155 yards long was nearly 1½ miles from the pit bottom and was advancing southwards in the solid on a rising gradient of 1 in 6.25 with a very slight rise from the intake gate to the return gate. It was started in September 1960 and the face had advanced 765 yards at a rate of about 10 yards per week. The No.5 face was advancing in the same direction and was 400 yards behind and 33 yards to the east of the No.2 face.
At the face, the coal was cut about 1 foot above the floor level by an electrically driven machine mounted on an armoured flexible conveyor. Until the 3rd. February 1962, the depth of the cut was 6 feet 6 inches but on that day the jib was changed and the depth of the cut increased to 7 foot 6 inches.
Coal in the stables was cut at the floor level by shortwall machines. After cutting all the coal was won by explosives and compressed air picks. The same type of explosive was used in taking down the ripping gate which was kept well up to the face. The normal cycle of face operations was as follows.
The afternoon shift advanced the face conveyor, drilled shotholes in the face, withdrew supports from the waste, drilled and cut the stables and ripped the intake gate. The night shift ripped the return gate, cut the face line and commenced filling. The day shift completed the filling.
The roof at the face was supported by friction type props set to corrugated steel bars 8 feet long. Additional frictional props were set as breakers at the edge of the waste which was completely caved between the six yards wide intake gate pack and the 8 yards wide return gate pack. The intake gate was 14 feet wide and 10 feet high and the return gate, 10 feet wide and 8 feet high. These were supported by arched steel girders which were tilted and backed with by fire-resistant wood boards.
The coal from the conveyor’s face was transferred to a belt conveyor in the intake gate. This was the first stage of a trunk conveyor belt system to the bottom of the shaft. Some supplies reached the face from the surface drift and the intake gate, using the tub pack provided in that gate. Other supplies came down No.3 shaft and along the main intake airway in the tube to the cut-back. There the tubs passed through separation doors into the return airway where they were taken by an endless rope haulage to a point in the return some 300 yards outbye of the face-ripping. The tubs were then hauled inbye by an electrical engine direct rope engine situated near the face-ripping.
The ventilation records show that for some months before the explosion, the quantity of air as measured at a point in the intake gate 10 yards outbye from the face was slightly in excess of 20,000 cubic feet per minute. The records also show that during the thirteen months before the explosion, the firedamp content of these samples collected at a point in the return gate, 10 yards from the face varied between 0.4 and 0.7 percent but occasionally it was outside these limits.
Firedamp was drained by holes 120 feet long bored from the return gate into the shale above the waste at intervals of 35 yards. The holes were connected to a pipe 6 inches in diameter which was increased to 8 inches in the main return to the bottom of No.2 shaft and to 12 inches in the shaft. The firedamp was drawn from boreholes and discharged to the atmosphere by an exhauster on the surface. The quantity of gas drained averaged over 100 cubic feet per minute which represented about 55 percent of the make firedamp on the face.
The practice was to fire shots in the intake gate stable and also in some of the top coal on the face during the night shift to facilitate the start of filling operations, The return gate stable was fired either at the end of the night shift or at the start of the day shift according to how work had progressed. The remainder of the top coal followed by the bottom coal was fired during the day shift. The intake gate ripping was fired on the afternoon shift and the return gate ripping on the night shift.
In addition to the deputies who were not authorised to fire more than 10 shots per shift, there were shotfirers available on the day and night shifts and they each carried 40 detonators. In order to ensure that all demands for shotfiring were met, some of the shotfirers shifts were “staggered” with the main working shifts. As a result, there were frequently three shotfirers available at the beginning of the day shift.
The volatile content of the coal was 32 percent but the management had not formally declared this figure to His Majesty’s Inspectors and were thus required by law to ensure that a minimum of 75% incombustible materials was always present on the roof, side and floor of the roadways. At the last statutory sampling before the explosion, the incombustible content of most of the road dust samples was well in excess of the minimum required.
A stone dust barrier consisting of seventeen heavy shelves and eight light shelves covering about fifty yards of roadway were in the intake gate, about three hundred yards from the ripping. One hundred yards further, inbye there was a similar barrier of twelve light shelves. Automatic firedamp alarms were not used at the time of the explosion.
The general impression created by the witness was that the ventilation of the district had always been good and that men working on the face were obliged to wear coats or woollen garments to keep warm. There were no reports of firedamp having been detected other than occasionally in the return gate stable.
The day before the explosion, on the afternoon shift of the 21st March, the face conveyor was moved over, the waste drawn off, the face and stables drilled, the coal in both stables cut and the intake gate ripped. Mr. J. McKillop, the deputy in charge of the district, fired the ripping. In his report for the shift, he noted that there was a broken roof in the intake gate stable and his recollection was that the waste behaved quite normally in that as the supports were drawn it hung first for ten yards and then stared to cave progressively throughout its full length.
On the following night shift, the district was in a charge of Mr. R. Jackson, a deputy, and the main operations in progress were the cutting of the coal on the main face line and the ripping of the return gate. Work proceeding normally and in spite of a late start, cutting was completed before the end of the shift.
The jib of the machine was drawn out of the cut and the electric cable detached and taken into the return gate. Jackson, who examined the district twice during the night shift observed nothing unusual but did notice a slight roof break of about 2 to 3 inches throughout most of the face.
His last visit to the return gate stable was soon after 6.30 a.m. and although the stable had been cut on the previous shift he found no firedamp there. In his opinion, the ventilation was very strong. He travelled the return gate twice and on both occasions observed three empty tubs and two bogies near to the direct rope hauler and attached to the rope. There were a few small roof cavities in this gate, apparently caused by the deterioration of the backing boards, which had allowed roof dirt to fall through.
Two shotfirers, Mr. R. Latham and Mr. R. Hutchinson started at normal shift time and a third shotfirer Mr. R. Ridge came on an intermediate shift starting after midnight. Each fired forty shots distributed between the intake gate stable and the main face line. No shots were fired in the return gate stable although nine holes had already been drilled there. None of the shotfirers found any firedamp during the shift. In addition to the shots in the coal, the deputy himself fired a few in the return gate ripping.
To facilitate packing the natural from the return gate ripping Mr. G. Rimaldi, who was in charge of the rippers took down brattice sheet which had been erected to deflect the air into the return gate stable. This sheet was not re-erected because Rimaldi and his team failed to complete the building of the pack. The unpacked ripping debris was retained in the highly inclined gate behind a wooden barrier about three feet high. It is worthy of note that Rimaldi confirmed the deputyÕs statement that there were three or four tubs at the head of the return gate.
At about 10.15 p.m. Mr. J. Feltell, an attendant started up the booster fan and ran it ran about an hour. This had no significance in relation to the ventilation for the district, it was part of the care and maintenance routine of the fan.
Mr. Jackson left the return end of the face just after 7 a.m. and at about 7.30 a.m. he met Mr. J. Halstead, one of the incoming day shotfirers, at the junction of the No.2 return with the No.1 return. He told Mr. Halstead about the holes which were drilled and ready for firing in the return gate stable. At the deputies’ Meeting Station at the cut-back, Mr. Jackson discussed the condition of the district with Mr. S. Bullen the coming day shift deputy.
The workmen of the day shift reached the face about 8 a.m. on the 22nd, March, some by the return and others by the intake gate. With one exception, none of those who went on to the face from the return gate recalled seeing a brattice sheet in the position near the return gate stable. In addition to the deputy in charge of the district there were two shotfirers on the face, Mr. J. Halstead at the return end and Mr. K. Clarkson at the intake end, nineteen fillers with Mr. J. Murray as captain, two conveyor attendants Mr. T. Isherwood at the return end and Mr. P. Ince at the intake end, a conveyor maintenance man, Mr. J. Allen and a mechanic Mr. G. Hartley. In the intake gate were Mr. J. Pollard, Mr. W. Bradshaw and Mr. T. Chapman who were working at a floor dinting about five hundred yards from the face ripping.
Two men, Mr. D. Rushton and Mr. R. Dunston were completing the building of the return gate waste side pack with ripping debris left by the previous shift. In the return gate was Mr. D. McGoogan, a mechanic who had been instructed to make an extension piece of the rope on the direct electric hauler. His machine had recently been moved nearer to the face and the existing rope was not long enough to reach the return wheels of the endless haulage. Also in the gate were four electricians Mr. G. Pickles, Mr. R. Howarth and Mr. P. Tinsley who were engaged in hanging a new length of armoured cable and extending the signalling system for the newly positioned electric hauler. Mr. J. Barritt was responsible for supervising this work and for the routine maintenance of the electrical equipment in the district. According to Mr. J. Holden, the driver of the endless rope haulage engine, three lads, R. Taylor, J Connings and J. Forrest left that cut-back early in the shift to collect tubs that had been left up the No.2 return gate.
The evidence suggested that the conditions on the face in the early part of the shift were quite normal. There was no evidence of roof weighting, of floor movement or of broken coal other than that constant with the firing of shots on the previous shift. The fillers who gave evidence said that on the face line the ventilation was normal and indeed many were wearing jackets and pullovers. With the exception of J. Madden and A. Fisk, none of the fillers heard any shots fired that morning.
The colliery records showed that flame safety lamps of the re-lighter type had been issued to the deputy and two shotfirers and on the non-lighter type to Murray and Fisk. Automatic firedamp detectors had been provided and used at the colliery but were not available on the day of the explosion because some had become defective and all had been sent from the colliery for repair or overhaul.
When the day shift overman, Mr. H. Lister, reached the intake end of the face at about 9 a.m., he found that there had been difficulties with the running of the face conveyor. Apart from a visit to the return gate ripping where he tested for firedamp, he appeared to have been entirely preoccupied with these difficulties. While at the return end of the face, Mr. Lister spoke to Halstead, the shotfirer, who, in the course of some jocular conversation said that he had already made a start by firing three shots. Lister did not go over the conveyor to the face of the stable but he gained the impression that some of the coal was down because he saw it being turned back into the stable by men who were working down there. He left the return end just before 9.45 a.m. to travel down the face.
Madden who was the last filler at the return end of the face line said that he was told by Rushton and Dunston as they were passing props to him over the conveyor, that shots were about to be fired and that they were going down the return gate to take shelter. Madden assumed that he was expected to act as a sentry and regarding himself as being in a safe position continued to pull down some coal. Fisk who was working with J. Robinson in the return gate stable said that he did not find firedamp when he tested there at the beginning of the shift. He helped Halstead to stem “nine out ten shot holes” in the stable and thought that the shotfirer coupled up the leads from the shotholes in series to the shot firing cable. Fisk went about 50 yards down the return gate to what he regarded as a safe place and he believed Halstead stopped some 10 yards short of this point.
When the explosion occurred, Murray was filling coal at a point on the face about thirty yards along from the intake gate stable. He thought it was about 9.40 a.m. when he heard a sound like the bursting of a compressed airline. The air reversed but the normal direction of the current was quickly restored, and although there was a considerable amount of dust in the air he did not see any flame.
The fillers along the face described in their own ways their experiences of the blast and the reversal of ventilation. Madden said he was flung over the conveyor and enveloped in “swirling soot” which came rushing onto the face from the return end. He felt certain that the noise he heard was that of a shot being fired. Although he had never before experienced a firedamp explosion, he thought that it would produce a far large “Bang”. Fisk sheltering in the return gate also thought the sound he heard was that of a shot being fired. He said he heard the shotfirer turning the key in the exploder immediately before and he naturally associated this with the event. So far as he could be expected to remember what happened in such circumstances. Fisk seems to have retained an impression that the blast came towards him from the face.
Pollard working on the floor dinting in the intake gate had just looked at his watch at 9.45 a.m. when he heard what he described as a thud and he and his mates Bradshaw and Chapman were enveloped in dust. The air reversed but its normal direction was resumed very quickly. Pollard, whose evidence about the time of the explosion was confirmed by the recordings on the methane drainage chart, realised that something serious had occurred.
Bradshaw telephoned the surface the three men went into the intake gate on to the face. After going sixty yards along the face, Pollard realised that there had been an explosion immediately went back to a telephone and informed someone on the surface probably B. Kennedy the acting manager. He rejoined his mates and together they made their way along the face and into the return gate doing all they could to comfort the survivors, while stretchers and first aid equipment were being bought. Although in the course of his search for survivors, Pollard was obliged to move some bodies, he distinctly recollects it was not necessary to move that of Halstead the shotfirer who was found face downwards with his head outbye, lying on debris in the vicinity of the ripping.
Mr. J. Holden, the engine driver at the cut-back, said at about 9.40 a.m. he attempted to “inch” the haulage rope but after moving it very slightly it held fast. Some five minutes afterwards he was enveloped in dust and both doors in the cut-back were blown open. Mr. R. McKenna, who was working in the cut-back at the time was sure Mr. D. Whitehead, who had been a deputy for many years and was now engaged on the supervision of fire-fighting equipment and stone dust barriers, was at the point in the main intake some two hundred yards outbye of James Bradley’s junction when he felt the reversal of the air. He went to the cut-back where he was told on the telephone that something had happened in No.2 District. Ongoing through the separation doors into the return, he tested for firedamp and estimated four per cent in the general body of the air. He then went up the intake along No.2 face and into the return gate giving what assistance he could.
The Boothstown Rescue Station’s No.1 Team was practising at the nearby Huncoat Colliery and were summoned at 10.15 a.m. They arrived at the colliery 10 minutes later. The Station’s No.2 Team arrived from the Rescue Station some 25 miles away at 11.10 a.m.
The No.1 Rescue Team was captained by Mr. L. Wheeldin and accompanied by Mr. W. Rawstron, the Group Manager. They went into the pit by the surface adit at 10.35 a.m. They entered the main return airway at James Bradley’s Junction where they found 0.006 carbon monoxide but no firedamp in the general body of the air. The ventilation was good and although there was no smoke or haze, there was a slight smell resembling that found after a fire. The team proceeded towards No.2 face by the return gate.
The No.2 Team captained by Mr. W. Sturgeon and accompanied by Mr. L. Hampson, the Rescue Station Instructor and Mr. E. Whatmore the manager of Bank Hall Colliery, went underground by the surface adit at 11.15 a.m. They travelled the main intake airway where they passed a number of stretcher parties, along the face and a short distance down the return gate, Sturgeon reported among, other matters that he saw a shotfiring exploder on top of the retained debris near the return gate stable but he was not clear whether or not it was connected to the terminals.
Because of the relatively slight disturbance by violence and the absence of fire and the rapid dispersal of the afterdamp the affected area was re-entered very soon after the explosion. True to the traditions of the industry many willing helpers were immediately available to give first aid treatment including the administration of morphia to the injured. Very soon afterwards all the survivors were examined underground and further treatment was given where necessary by the nursing sister and the Group Medical officer. The positions of those who died in the pit were determined by the rescue teams.
Those killed:
- Christopher William Brown, aged 55 years, driller,
- Sampson Henry Bulle, aged 44 years, deputy,
- James Cumming, aged 19 years supply man,
- Robert Dunston, aged 26 years, ripper,
- Stanley Faulkes, aged 41 years, filler,
- John William Halstead, aged 53 years deputy and shotfirer,
- George Hartley, aged 32 years, mechanic,
- Raymond Earnest Howarth, aged 20 years, electrician,
- Tom Isherwood, aged 49 years, face supervisor,
- Donald Stewart McGoogan, aged 28 years, mechanic
- Garry Pickle, aged 22 years, electrician,
- John Robinson, aged 24 years, filler,
- Donald Rushton, aged 33 years, ripper,
- Robert Shuttleworth, aged 33 years, filler,
- Ronnie Anthony Taylor, aged 16 years, supply man
- Benjamin Walsh, aged 25 years, filler.
Died from injuries:
- John Grieg Barritt, aged 23 years electrician,
- Joseph Forrest, aged 17 years, supplies man,
- Peter Tinsley, aged 16 years, apprentice electrician.
Immediately after the recovery operations had been completed H.M. Inspector of Mines, accompanied by representatives of the management and the workmen carried out a preliminary inspection of the greater part of the mine including the explosion area. Shortly afterwards the Inspector and scientists from the Safety in Mines Research Establishment made other inspections of the explosion area. Neither inspection revealed any obvious point of ignition, ignition agent of the presence of firedamp. The Inspector and the scientists commenced and extremely detailed investigation which lasted two months
A detailed picture of the explosion area emerged from these investigations. Specimens of fibrous material collected in the intake gate were examined microscopically and did not show signs of having been subjected to heat. Although there was a thin layer of explosion dust on the conveyor gate, the dry stone dust on the barriers had not been disturbed.
Specimens collected at points along the face indicated that the flame had travelled down the face to within about thirty yards of that stable. Much of that part of the face affected by flame and there were unmistakable signs of coking on the intake sides of the props, an indication that flame had come from the return side. Detonator leads coming from charged shotholes in the return gate stable showed obvious signs of charring on the first twenty yards of the face from the intake but further along the face where signs of some violence, although roof supports had not been affected.
Microscopic examination of fibrous specimens collected from an area between the face-ripping and a point 550 yards outbye, showed signs of exposure to flame. Beyond this point to the junction of the No.5 District return, specimens had been subject to some heat but had not been carbonised. There were signs of the blast near the ripping but the evidence as to the direction in this area was not positive. In the length of gate between points 28 yards and 180 yards outbye of the ripping, there were unmistakable signs of blast in the direction of the face. Outbye of this area, although there were a small number of small roof cavities and the floor, was strewn with fallen stone, backing boards and other debris there were no indications of blast up to a point 280 yards from the ripping.
There was an electric section switch that had been moved outbye presumably by the blast. In the next 40 yards of roadway, the damage from the blast was the most severe in the whole of the affected area. In this length, a number of badly damaged tubs and bogies were found derailed and smashed near the return wheel of the endless rope haulage. The wheel the carrying frame and the arch girder supporting it had all been displaced in an outbye direction but there was no sign of abrasion on the return wheel or its framework. For a further 200 yards outbye signs of damage were much less in evidence but there had evidently been a strong blast some 650 yards from the ripping where a tank had been displaced. From there to the junction with No.5 District return there were signs of only a slight blast.
Nowhere in the area was there any indication of a slow-burning of rich firedamp/air mixture. The results of the examination suggest that the blast had affected in varying degrees nearly 1000 yards of face and roadway of which 680 yards had been exposed to flame.
Ventilation measurements made shortly after the explosion indicated that the quantity of air leaving the district varied from 14,200 to 15,000 cubic feet per minute. The firedamp content of this air as measured by a methaneometer was between 0.6 and 0.8 percent. The colliery records show that before the explosion in the quantity of air passing was higher and the percentage of firedamp lower but the actual make of firedamp was about the same. Excluding that being drawn off by the drainage system, this was about 100 cubic feet per minute.
Discarded firedamp drainage holes were sometimes sealed by the insertion of wooden plugs but some had been left unsealed. Six of the unsealed holes in a length of from 321 to 709 yards from the face-ripping were examined for firedamp issuing from them. By using a methaneometer and probe firedamp was found in five holes but only one at 472 yards from the ripping gave any indication of continuous flow. This was small in quantity but up to 30 percent was detected at the mouth of the hole. Relatively high concentrations of firedamp were found in a number of small cavities in the roof of the return gate but it was estimated that the total volume of pure firedamp in these cavities could not have been more than 50 cubic feet.
On the 24th of March, one of H.M. Inspectors made a ventilation survey in the return gate stable without a brattice sheet in position. By using artificially produced vapour clouds as a tracer he found that only a small proportion of the air leaving the face entered the stable. Here there was very marked recirculation. Using a methaneometer with a probe attachment the inspector found high concentrations of firedamp at a number of points between the roof and the top of the fallen coal but the total quantity involved was very small. On the same occasion, the inspector using the same equipment made determinations of the firedamp content in the waste some of them from points 7 to 8 feet above the seam roof level. In no case was the concentration higher than that in the general body of the air at the face.
Although the quantity of air leaving the district immediately after the explosion was found to be substantially less than that record from the last statuary measurements made before the explosion later measurements showed that the quantity had increased to between 16.000 to 17,000 cubic feet per minute with a firedamp content of 0.4 percent.
Because of the frequency with which the men and materials were known to pass through doors at the cut-back and men through the doors at James Bradley’s Junction, it was decided to measure the effect of opening these doors on the ventilation district. Two tests were carried out one with the doors at James Bradleys Junction fully open and the other with the doors at the Cut-back partially open. In the first test the normal quantity of air reaching the face was reduced to 6,000 cubic feet per minute and in the second by 5,000 cubic feet per minute.
In the course of the investigation, two Hessian sacks were found each containing the same type of Eq.S explosive in the cartridge form. One near the intake gate ripping contained 12 pounds and the other near the return gate ripping contained 56 pounds.
Although the first 14 yards of the face from the intake gate stable 10 shotholes had been drilled in the bottom of the coal, Nine of these had been charged and stemmed and a single shot exploder with connected cable was lying between the ninth and tenth holes.
In the return gate stable, seven shotholes had been drilled and six of them charged and stemmed. The charged shotholes were disposed of in two groups, two near the rib side and four to the left side of the stable. In the short length between the two groups, there was a heap of broken coal lying against the face. It was clear from the evidence in the roof and face that at least two shots had been fired in the vicinity. Of the group of four shotholes the one immediately next to the broken coal and about 12 feet from the face buttock invited particular attention.
It was observed that the coal on the loose side of this hole was fractured by innumerable fine cracks. When this coal was removed by hand a plug or stemming at the front of the hole and three cartridges of Eq.S explosive were revealed. The latter were impacted together as though they had been subjected to pressure from the back of the hole, and the inner end of the last cartridge was covered by a coating of coal dust 1/8″ thick. The shothole was subsequently found to extend 12 inches beyond the last cartridge but this section was empty. A primer cartridge was not found and there was no evidence to suggest that the shot had blown out laterally. Two detonator wires were found in the hole one reached only as far as the stemming but the other extended to the inner end of the recovered part of the charge.. Nothing unusual was observed in the condition of the remaining five charged holes and they were subsequently fired without incident under the supervision of H.M. Inspectors.
A shotfiring cable without detonator leads attached extended from the face side of the conveyer over a roof bar under the return gate ripping onto the ripping debris where the remainder was tied in a hank with one of the leads connected to a single shot exploder. A shotfiring exploder key was later found in the clothing of Halstead, the shotfirer whose body was recovered from nearby.
A case subsequently found to contain 31 detonators was also found in Halsted’s clothing. Some of these with others were taken from the colliery magazine 25 in all were sent to the Armament Research and Development Establishment, Woolwich for X-ray examination and test. They were found to be in normal in all respects.
Explosive from the pit and from the colliery magazine, when tested for behaviour and composition, proved to be normal. Tests for sensitivity to initiation of detonation on some of the explosive referred to in paragraph 51 showed that it had not deteriorated.
The five safety lamps and 53 electric cap lamps (some incomplete) recovered from the district were sent for test. The flame lamps and 28 of the cap lamps were found to be in approved condition securely locked and in working order. The remainder of the electric cap lamps had sustained some damage but this was considered to have been caused by the explosion.
Smoking materials were not found either during the underground investigation or when the effects of the victims were examined on the surface. No combustible material was found. No electrical defect was found. All signalling and exploders were found to be in good condition. The apparatus was examined to look for frictional heat and all was found functional. The seams included pyrites nodules known locally as “bobbers” and ignitions of firedamp had been known at the colliery attributed to cutter picks striking them. Because of smears left by aluminium alloys left with rusty steel a thermite reaction could arise. A fire hose nozzle was tested and found that it could leave aluminium smears but there was no indication that it had done so. In the length of the return gate ripping there were 18 metal foils from the wrappings used for confectionery and chewing tobacco. When pieces of the specimens were submitted to glancing blows with rusty steel in a firedamp atmosphere ignition was obtained in all but two specimens. These foil wrappings which are generally of aluminium usually have paper backing sometimes waxed where this backing was retained ignition could not be obtained.
The two specimens which had signs of fusion when picked up 300 yards from the return gate ripping. The signs of fusion were very similar to the signs on the pieces of aluminium foil which had given incentive flashes when tested.
The state of the roof was the same before and after the explosion. The roof breaks observed at the face by the afternoon and night deputies were not accompanied by marked displacement and were not unusual. the deputies described the wastes a behaving normally. The small cavities in the gates were attributed to the force of the explosion.
Mr. F.J. Hartwell, the Senior Principal Scientific Officer in charge of the S.M.R.E. examination summarised the point of ignition and the spread of the explosion. These were based on three facts. First, none of the fibrous material had been exposed to flame for more than a very short time. Second, at no point in the explosion area was there evidence of slow-burning by rich firedamp and third, there had been a rapid moving of flame accompanied by considerable violence although not so great as would have been expected from the most explosive mixture of firedamp and air with a relatively “quiet zone” between 180 yards and 280 yards outbye of the return gate ripping.
These three facts led to the belief that the explosion originated in the “quiet zone”. The signs were that the flame had travelled outbye from this area with some violence to a point about 550 yards from the face-ripping and possibly less violence inbye to the return gate stable. Here it was probable that there had been added firedamp which would have added to the violence sufficiently to raise some coal dust along the face contributing to the spread of the flame and blast in that direction.
Mr. Hartwell added that there might have been firedamp in the return gate stable and that flame from such an ignition could have blown out onto the face causing a minor coal dust explosion there. If this did occur, a flame from the stable could have been propagated down the return gate in a “trail” of firedamp along the roof, to a body of firedamp which would have exploded with flame and blast in both directions.
Either possibility would have required a presence in the return gate of a reasonably well-mixed volume of firedamp and air. The violence of the explosion was of 8 percent mixture of gas and air. He estimated that about 2,000 cubic feet of firedamp would have had to be present to have remained undispersed it would have appeared rather quickly.
There was no scientific evidence to show where the firedamp came from but he thought that the most probable place was along the face or the return gate stable. Dr. Willett for the N.C.B. thought that it came from “either the sold coal in the vicinity of the stable or the waste”. Mr. Clough, H.M. Divisional Inspector of Mines was firmly of the opinion that it came from waste because neither the face nor in the return gate stable were there strata breaks or displaced coal which were the more common signs of a rapid emission.
All were of the opinion that only frictional heat and explosives need be considered as the means of ignition. Mr. Crawford of N.A.C.O.D.S. suggested that the firedamp had been ignited by a frictional spark or thermite reaction as a result of vehicles running uncontrolled down the return gate. No other form of frictional heat was considered as a possible source of ignition.
Mr. J. Gormley for N.U.M. and Mr. Clough were both of the opinion that the shot fired in the return stable was responsible for ignition. Shotfiring operations were in progress when the explosion occurred. Some of the men that died were grouped some little way down the return gate as if sheltering from shotfiring and Madden and Fisk thought that the explosion followed a shot. However, if the explosion occurred after a shot the shotfirer must have had time to return the firing key to his pocket and this was found not to be the case.
Mr. Clough thought the ignition was in the stable would have been from the gas from broken coal and that this flame, in turn, ignited gas passing from the face into the return gate after being emitted from the waste. In these circumstances, it was concluded that Halstead would have had time to return the firing key into his pocket and to begin returning to the shotholes before he realised that gas was burning in the stable.
In conclusion, the commissioner was not able to give an entirely satisfactory explanation either of the sources of the firedamp or of the means of ignition.
It was accepted that the explosion was caused by firedamp present in the return gate. The possibility that this was caused by an interruption of the ventilating current would mean that the ventilation would have to be stopped for two minutes and there is no evidence that this occurred.
In considering the possibility of a rapid emission of firedamp into the return gate stable it was possible that the required explosive mixture could have been formed in the return gate. On ignition, the blast ahead of the flame travelling up the return gate could have dispersed and rich firedamp in the stable as to cause it to flame and continue the explosion with the help of coal dust along the face.
Firedamp from the high level in the waste could have been pushed out onto the face but it was felt this would have required a heavy strata movement which would be audible but there was no evidence of this. An emission from the waste could, however, have taken place quietly had the firedamp been hanging close to the edge of the waste but after the explosion efforts to establish the location of the firedamp were unsuccessful even though probes were pushed up into the waste to a distance of 7 to 8 feet above the seam roof level.
Two other possible sources of firedamp were considered. The first is the return gate ribside. A sudden emission of gas would normally be accompanied by breaks in the coal and surrounding strata. The fact no such breaks were found after the explosion is not however conclusive proof that they did not exist. They could have been near the ribside but concealed by packed material. The second possibility was that could have been some unplugged methane drainage holes. There were five such holes in the return gate between 200 and 350 yards outbye from the face. Separation of the upper beds resulting from the working of No.5 face could have made rich firedamp available to these holes. Relatively high pressures would have been needed to emit the firedamp but it was not thought that this had occurred.
As to the possible causes of ignition other than explosives and frictional heat all others could be dismissed. The use of explosives has long been the possible cause of ignition of gas and there was ample evidence that there was shot firing in the return gate stable at the time of the explosion. It was clear that shots in the stable were fired from a point immediately outbye the ripping debris. The position in which the body of the shotfirer was found that is on top of the debris, face downwards with his head pointing outbye and with the shotfiring key in his pocket suggests that after the explosion occurred he was either going towards or returning from the stable. At the time Fisk was sheltering in the return gate outbye of the ripping said in evidence that the blast came from the stable. The commissioner was satisfied that the rate of emission of the firedamp could have been such as to create adverse conditions in the vicinity of the stable between the shotfirers examination and the firing of the shot.
If shot firing been the cause of the initial explosion, it would have required a flame from firedamp ignited in the stable to communicate with and explode a mixture farther down the gate. The pattern of the blast showed marked signs of movement towards the face does not rule out this possibility as a blast from a minor explosion in the return gate stable would have been masked by the effects of a much larger explosion down the gate. This is, of course, presupposes two explosions and it is supported by a witness who gave evidence that the doors at the Cut-back opened and closed twice.
A great many pieces of foil of the type commonly used in the wrapping of confectionery and chewing tobacco were found in the return gate including some in the “quiet zone” referred to by Hartwell. The S.M.R.E. showed that if this material was laid on rusty steel and struck a glancing blow with a hammer a thermite reaction, capable of igniting firedamp may result. Two pieces of foil found immediately on the outbye side of the zone showed signs of fusion which would result from the thermite reaction. No pieces showing signs of fusion were found in the zone but this was not proof that none was present.
In considering whether the firedamp was ignited by frictional heat it must be remembered that at the beginning of the shift there were empty tubs at the top of the return gate waiting to be taken down to the return wheel. There was evidence that three supplies lads had been sent down early in the shift to collect tubs and that the rope itself which was to be lengthened was found to be fully extended after the explosion. The rope would not have been drawn by hand down the gate solely for recapping by the mechanic. It was more likely that the supplies lads used it to lower the tubs as far as possible and in this event, the tubs would then have been at a point not more than a few yards from the outbye fringe of the zone. Had the tubs run uncontrolled from this point and ignited firedamp either by running over aluminium foil or by violent impact with other material the resulting ignition would not have produced the flame and blast pattern described by Hartwell.
The conclusion was that there was either one explosion predominantly of firedamp in which coal dust played a little part initiated at a point 180 yards outbye of the face by thermite flash from aluminium foil or two explosions, a minor one of firedamp and coal dust initiated by shotfiring in the return gate stable followed almost immediately by a major explosion of a large body of firedamp/air mixture in the return gate.
The danger of sparking from aluminium alloys had been known for some ten years and steps had been taken by the N.C.B. to limit as far as possible the use of equipment made from these alloys to situations underground where the danger of gas was remote. In view of the evidence from this disaster, it was felt that a revision of the instructions, with particular reference to aluminium equipment, should be made. Portable drills should certainly be considered since I understand that manufacturers can now produce then constructed of steel or brass.
The use of metallic foils in wrapping confectionery and tobacco is not clearly within the control in the N.C.B. or the mine owners. Dr. Willett in his submission suggested that various associations and organisations in the industry should jointly consider steps which might prevent aluminium foil wrappings from being taken underground.
It was recommended that:
- The N.C.B. should undertake further investigations into the effect of borehole drainage on the movement of firedamp where total caving is practised, including the possibility of using lower inclination boreholes aimed at exhausting from the waste cavitation in addition to boreholes into relaxed strata and the continuous monitoring of the firedamp content in return airways from such faces.
- Mangers of collieries should ensure that stables are always ventilated.
- Managers of collieries where shotfiring forms one of the principal face operations should review current shotfiring practice and ensure that not only explosives used are efficiently but that the circumstances are such that the shotfirers are not tempted to disregard the requirements of safety.
- Every effort should be made to hasten the development of a robust automatic firedamp detector which is easily maintained and gives a strident audible alarm.
- The N.C.B. should further revise the restrictions imposed on the use of aluminium-based alloys so as to exclude them from the face workings from the return roads and from within 300 yards of the face in all other roadways.
- The several associations and organisations in the industry should conceder ways and means of preventing aluminium foil wrappings from being taken below ground in permitted light mines.
REFERENCES
The report of the causes and the circumstances attending the explosion which occurred at the Hapton Valley Colliery, Lancashire, on the 22nd March, 1962 by H.S. Stevenson, B.Sc., M.I.Min.E., H.M. Chief Inspector of Mines.
Colliery Guardian, 6th December 1962, p.717, 13th December, p.748, 27th December, p.813.
Information supplied by Ian Winstanley and the Coal Mining History Resource Centre.
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