BICKERSHAW. Leigh, Lancashire 10th. October, 1959.
On the 12th November 1959, Colonel R.M. Barlow, H.M. Coroner of the County of Lancaster, Bury District resumed his inquest on the bodies of the five men. A verdict of “Misadventure” was recorded in each case, and medical evidence showed that all five men died from carbon monoxide gas poisoning.
The Inquiry was made by Mr. R.H. Clough to the Right Honourable Richard Wood, MP., Minister of Power, in accordance with your direction given under the terms of Section 121 of the Mines and Quarries Act 1954.
Owing to the circumstances immediately following the explosion which demanded the isolation of further stoppings of the affected Plodder Seam, there had been no physical examination of the scene of the explosion after rescue operations were completed, other than a necessary brief examination made by men wearing self-contained breathing apparatus,
Bickershaw Colliery was at Leigh, Lancashire and was one of the No.3 Group of the No.2 (Wigan) Area of the North Western Division of the National Coal Board. The following Area officials under Section 1 of the Mines and Quarries act 1954, for the purpose of fulfilling the responsibilities of the N.C.B. under the Act were the Area General Manager, Mr. H.E. Clegg, the Area Production Manager, Mr. E. Small, M.B.E., and the Group Manager, Mr. J. McGann.
At the time, Bickershaw Colliery was served by four shafts numbered 1, 2, 3, and 4. Numbers 1 and 2 shafts served one part of the mine and Nos. 3 and 4 the other. Both parts have separate systems of ventilation but are accessible to each other below ground. Under the terms of Section 168 of the Mines and Quarries act 1954, the two parts are regarded as separate mines, each with its own manager. The manager of No.1 and 2 was Mr. A. Miller, and Mr. J. M. Lawson was the manager of Nos. 3 and 4. A statutory notice of approval had been issued setting out the respective spheres of responsibility of the two managers. In particular, the surface works are the responsibility of Mr. T. W. Allison, but who did not shoulder the direct responsibility under the Act.
The explosion took place on the 10th October 1959 in the Nos. 3 and 4 workings and in particular to the Plodder Seam. The Plodder (sometimes known as the Ravine) Seam had a worked section at Bickershaw of about 6 feet. It lies immediately over the High Yard Seam. These two seams, and their associated dirt bands, have an overall thickness of 18 feet. The Plodder Seam is well known in the coalfields as one liable to spontaneous combustion, particularly in the Wigan and Leigh areas, and there is at Bickershaw a long experience of trouble from this cause. With seams as close together as the Ravine and the High Yard, spontaneous heating could occur in the individual working of either, since the extraction of any one is bound to expose, in part, the other. The risk of self-heating is often associated with such thick seams in close proximity.
At Bickershaw Colliery the Plodder Seam was developed in a south easterly direction on a line of almost full dip at an average gradient of 1 in 7. By 1959 a large amount of extraction had taken place and large goaf areas formed, progress was by a developing face to the dip with wing faces advancing east and west respectively.
At the end of August 1959, only two longwall faces were working in the Plodder Seam, Nos.1 and 2 Dip Faces with a combined output of about 550 tons per day. The only other accessible face was the No.9 east, which ceased production on the 14th. August 1959. It was still being ventilated, and a small team of men were engaged in salvaging material. Of the three open faces, No.2 was ventilated by an air current separate from the others, while another split of air was conducted, first along No.1 Dip Face after which it passed into the Main Level of the No.9 East Face, where it was augmented by some intake leakage from the No.4 Brow. The quantity of air ventilation No 9 East, when last measured on 21st August 1959 was 14,700 cubic feet per minute, and the average percentage of inflammable gas in the return airway from this face as determined at a point 10 yards from the face on No.9 East Top Level was 0.95 percent. Of this gas some was contributed on No 2 Dip Face, the air on which normal contained about 0.3 percent in a quantity of 12,500 cubic feet per minute. a rough estimation suggests an average emission of firedamp on No.9 Face of the order of 100 cubic feet per minute.
The No.9 Face had advanced about 800 yards alongside the goaf of the old abandoned No.8 Face to the rise side, keeping contact with this goaf as it progressed, while the No.9 right hand or dip side was forming a coal rib. Both Main and Top Levels of No.9 Face were supported by steel arches. The general dimensions of the Main Level were 13 feet wide by 10 feet high, those of the Top Level, 9 feet wide by 7 feet high at the face, but, owing to the severe crush probably associated by the nearness of the No 8 Goaf it was reduced to about 3.5 feet by 4.5 feet for about 200 yards of its total length.
The No.8 East Face, when working, was 160 yards in length. It ceased production on the 9th. August 1957 and stoppings were put in some three months later. These stoppings were later expanded by stowing of waste dirt and by October 1959, the No. 8 Top Level stopping was 150 yards long, and the No. 8 Main Level stopping, 100 yards long.
During the morning of Sunday the 4th October, a deputy Mr. F. Hodgson, accompanied by a workman as a travelling companion, was making an ordinary weekend inspection of the No.9 Face. These two men encountered the face by the Main Level (intake), travelled up the face, and then outbye the Top Level (return). Immediately on leaving the face at the Top Level, Hodgson noticed a smell of “heating” when he was about 3 yards outbye of the face-ripping lip. He also recognised some haze and seating on the roof at the higher side, adjoining the abandoned No.8 Face. These findings were communicated to the manager who subsequently made an examination of the place accompanied by the assistant manager, Mr. Allison, Mr Lawson decided that it would be practicable to deal with the heating by excavating or “digging out” the pack, and steps were taken at once to do this.
During that Sunday afternoon, and the three following shifts, men were engaged in removing the packing, and from the evidence of those engaged on this work, it is possible that this excavation eventually penetrated for some few feet at least, into what was originally the right-hand pack of the abandoned No.8 Face. About the heating, there was no doubt. The packing material taken out was hot and had to be quenched with water before being cast aside, and at one time or incandescence was observed by Mr. Allison and by one of the deputies immediately in supervision.
By the end of the morning shift of Monday, the 5th of October, it was decided that all the heated material had been removed and quenched and steps were taken to restore the roadway side by filling the excavation with sand, faced with a sandbag wall. All this was completed by the end of the morning shift on the 6th, by which time the road surfaces were observed to be sensibly cooler.
During the digging out operations, and the subsequent re-sealing of the affected part of the packing, atmospheric conditions were not unduly uncomfortable. Samples of the atmosphere from the general body of the air in No.9 Top Level on there turn side of the place where the heating was found did not, on analysis, give gaseous constituents of the character which might have been expected from the heated ground on the intensity actually observed. The carbon monoxide contained (0.0014-0.0036 percent) was not unduly high for the Plodder Seam at Bickershaw.
Although the management were convinced that the heated material had been successfully removed, the occurrence served as a warning that it was time for the No.9 Face to be abandoned and stopped off. Salvage operations were almost completed, and Mr. Lawson, therefore, decided to put in final stoppings.
It was the usual practice in the Plodder Seam at Bickershaw to seal off abandoned panels by first building stoppings in the levels some 70 to 100 yards inbye of the main airway from which they were sent out. Once the sealing of the panel had been completed, the remaining space outbye the stoppings is then used for the intermittent stowing of waste dirt, with the result that the stoppings were gradually increased in thickness until they could be faced with a masonry wall alongside the main airway.
It is also unusual when ordinary stoppings have to be built for members of the Central Rescue Corps to assist. This course was taken, not as an emergency measure, but because these men were trained in the building of stoppings and their help usually results in the stoppings being built more quickly. Since their training took account of fire and explosion risks, their procedure was always in accordance with these risks whether or not they are known to exist.
The building of the stoppings in the roads leading to No.9 Face was begun on the morning shift of Friday, 9th. October and work was continuous. The Main Level, the place selected was 72 yards from the No.9 scouring at point where the steel arched roadway was about 13 feet wide and 10 feet high. The stopping in the No.9 Top Level was 64 yards from the Scouring where the roadway was 5 feet to 7 feet wide and 3 feet to 3 foot 6 inches high. The stoppings were constructed mainly of sandbags with an intermingling of bags of dirt-filled on the spot. There were said to be reinforced with old arches or rails or whatever else was handy, both at the inbye end and throughout their length. During the erection of the stoppings the practice was adopted of leaving narrow tunnels about 3 feet square through the base of each stopping with the object of preserving some ventilation round No.9 face until the sealing could be completed finally and quickly plugging the tunnels simultaneously with further sandbags.
Both stoppings were complete except for the sealing of the tunnels by about 10 a.m. on the 10th October at which time the Top Level (the return) stopping was 11 yards in length, and the main Level (intake) stopping 8 yards in length. The final sealing of the tunnels was completed about mid-day, the intake at 12.15 p.m. and the return half an hour later.
When both seals were completed, the separation doors in No.9 scouring between intakes and return levels were opened to provide a free flow of air from the no 1 dip Face to the main Return Brow. The immediate result of this was that for 64 yards on the No 9 Main Level, and for 53 yards on the No.9 Top Level there was no positive ventilation. This would not necessarily produce at once a poisonous or inflammable atmosphere at the face of the stoppings since all the stoppings leak a bit at first, and there would still be a small flow of air through them if only because of a small pressure difference resulting from the difference in the level of the two stoppings. For the two “blind” ends of the outbye the stoppings the manager had made provision for auxiliary ventilation by installing fans should the need arise. However other events supervened and I do not think the operation of the fans would have changed the circumstances. However, as aside, I feel it my duty to say that auxiliary ventilation should have been put into operation as a prudent measure against the accumulation of dangerous amounts of inflammable or noxious gases following the arrest of the main ventilation by the stoppings.
The No.9 Face and parts of the two roads leading to it, were thus finally sealed off almost two months after coal production ceased, and four days after the heating in the Top Level had been dealt with. At about mid-day on Saturday, the 10th October, when the stoppings against the No.9 East Face had been finally closed, the one on the intake was some few yards short of the usual minimum length of 11 yards put on when the stoppings on old districts are first built. The manager, therefore, decided to continue with an afternoon shift of a small number of men to be engaged solely on the work of increasing the length of this stopping. The shift comprised two officials, two members of the Boothstown Permanent Rescue Corps, and nine other workmen.
When the building of this stopping had first begun the belt of the conveyor originally in use for coal transport along No.9 Main Level had been shortened to that place, and by running it in the reverse direction it could be used for conveying sandbags from the No.4 Brow Transfer Point to the stopping site.
Some of the men engaged in this afternoon shift were engaged in the actual building of the further length of the stopping. Others in the transportation of sand along the conveyor, and, farther outbye, others were preparing sandbags and taking them down the No.4 Brow from the Loading Point to the Transfer Point at the No.9 East Main Level. At about 4 p.m. there were five men near the face of the stopping, J. McLeod, the overman, F.B. Sargent the deputy, J. Dawber and R Evans, members of the Rescue Corps and H. Thomason, a haulage hand, while others were several yards away taking sand from the conveyor belt. The remainder of the men were distributed on various tasks between the Transfer Point and the No.4 Brow Loading point.
While getting on with the job, the men at the Transfer Point heard a thud coming from the direction of the stopping, and on going through the separation doors on this road they found a cloud of dust and fumes with the smell of burning. Eventually, some men emerged from the dust, and soon it was realised that five men near the stopping had been overcome in some way as the result of some kind of explosion. The men at the Transfer Point regained the air supply and the remaining group of men telephoned the surface while others reversed the conveyor belt so that the top belt travelled outbye, in the hope that someone disabled could perhaps make use of the belt to escape.
The telephone message reached the manager, Mr Lawson, at his home near the colliery. After making sure that the Permanent Rescue Corps had been summoned from the Boothstown Central Rescue Station, he left for the colliery. By this time, Mr. Allison, the assistant manager, had gone underground.
At approximately 4.25 p.m. a team of Five Rescue men from Boothstown went underground. They reached No.9 East by 4.50 p.m. travelling by foot down the No.4 Brow (intake), meanwhile, Mr. Allison was on the way and met two who had come from the affected area.
By this time some of the dust and smoke had cleared and a fresh air base was set up at the entrance to the No.9 Main Level (Transfer point). Arrangements were again made for the belt to be reversed, and the Rescue Brigade, wearing their apparatus, approached the Main Level stopping where they located the bodies of McLeod, Sargent, Dawber, Evans and Thomason, four of them together and the other a few yards distant. All appeared unconscious or dead and they were immediately taken to a fresh air base using the conveyor belt. On arrival there, artificial respiration was carried out in conjunction with the administration of oxygen but these measures proved unavailing. At 6 p.m. Mr. Bond, a Group Manager from a neighbouring group, Mr. Lawson, Manager, Mr. A. Cunliffe, Rescue Station Superintendent, and Dr. J. F. Erskine, the Area Medical Officer, arrived together at the fresh air base when the doctor examined the bodies of the five men and pronounced them to be dead. Arrangements were then made for the transport of the bodies to the surface and for the retreat of all persons from the seam.
However the atmosphere had cleared somewhat, the opportunity was taken by the Rescue Men to have a closer look at the stoppings. With their companion’s support, W. Sturgeon, the Captain, went into the main Level stopping and K. Shaw to the Top Level Stopping. Approaching the main level stopping, Sturgeon observed that flame safety lamps, although extinguished, were still hanging from roof supports, and that hanging water bottles were understudied. There was little evidence of violence. There was no flame to be seen, but at the stopping itself a hole was observed at the top about 3 feet wide and 1 foot in height, due, possibly to the displacement of part of the top layer of sandbags. From the top level stopping, Shaw reported that no displacement had occurred, and again no sign of flame or smoke. On these occasions, the opportunity was taken by these two men to collect a sample of the atmosphere at the face of each stopping. On analysis, the sample from the Main Level yielded among other gases, 0.016 percent carbon monoxide, and 0.46 percent firedamp, while that from the return stopping was much more lethal with nearly 3 percent carbon monoxide and 5 percent firedamp.
When all the men had been accounted for, and these conditions confirmed, Mr E. Small, Area Production Manager, who was then at the colliery, ordered a complete evacuation of the mine pending a decision on the next steps to be taken. All the men were out by about 9 p.m. after an arduous journey with the bodies of the five men through the No.4 Brow for about 2,000 yards against an average gradient of 1 in 8.
Later Mr. H. E. Clegg, Area General Manager, who was then at the colliery, having heard the principal facts of the occurrence. He decided that there should be no further exploration of the Plodder Seam because of the danger of a second explosion. It was thought that permanent stoppings should be put in at the top of the three airways serving the seam. Even if the termination of some working area had been considered, it would have been impossible to build further stoppings without placing them so close to the others as to incur a grave danger from a subsequent explosion.
The sites of the final stopping-off of the Plodder Seam were carefully selected, with the advice, among others, of Dr. H.L. Willett, Deputy Director-General of the Headquarters Staff of the National Coal Board, who had been called to the colliery. It was no part of the report to recount the final work except to say that it was conducted under full emergence conditions with men underground only in sufficient numbers to secure the expeditious erection of the stoppings.
The final closing if the stopping was completed at 11 a.m. on Tuesday, the 13th October, and, after a suitably long waiting period with no men in the mine, inspections were made of the stoppings periodically with a sampling of the atmosphere behind them and tests for leakage. This was followed by further measures to strengthen them.
Those who died were:
- John McLeod aged 28 years, an overman,
- Frederick Brian Sargent aged 27 years, a deputy,
- Henry Thomason aged 48 years, a haulage hand,
- Jeremiah Dawber aged 39 years, a member of the Permanent Rescue Corps,
- Reginald Evans aged 38 years, also a member of the Permanent Rescue Corps.
It was at once clear that an explosion had taken place within the area contained by the stoppings on No.9 East Main Level and No.9 East Top Level. No effects of violence had been observed except the displacement of part of the Main Level stopping. The survivors had seen dust and smelled something burning but had seen no flame. The deceased men had been overcome by carbon monoxide gas and their bodies showed signs of burning or other external injuries.
When the two stopping were first begun on Friday 9th October, there was some intermediate restriction of ventilation through No.9 Face and when they were finally plugged at about mid-day on the 10th, all ventilation would cease except for possible leakage through the stoppings. Now the estimated amount of 100 cubic feet of methane entering the air current per minute with normal ventilation might diminish with the cessation of ventilation bit it would continue to be the main cause of change in the atmosphere within the stopped-off area. With the completion of the seals the eventual production of an inflammable atmosphere was inevitable. Before such areas become sufficiently deprived of oxygen it can be assumed that the atmosphere, in its composition, passed through the inflammable range.
When Mr. Lawson, the manager, decided to seal off No.9 Face and roads, he was confident that the heated material found at the left-hand side of the No.9 Top Level had been sufficiently dealt with. Samples of the atmosphere from the No.9 Top Level continued to be taken until 7 a.m. on the 10th October, some five and a half hours before actually sealing took place. Although these samples were analyzed for carbon monoxide alone the amount of this gas found was not abnormally high. In fact over the whole period of 5th to 10th October, the average amount of this gas found here was 0.0022 percent, the maximum, on one occasion only, being 0.0063 percent. The site of the heating at the left-hand side of the No.9 Top Level was last seen some four hours before actual sealing took place.
There were, of course, other possibilities causes of ignition that spontaneous combustion. At the Inquest, the manager, Mr. Lawson, mentioned the possibility of frictional sparking occurring from a fall of material somewhere on the face or in the roads within the sealed area. Explosions of inflammable gas have been attributed to this cause when in the absence of any more positive indication such falls of material have been identified with similarly positive evidence of where the ignition took place. The question of sparking from electricity but the evidence of an electrician from Bickershaw was to the effect that all electric power was cut off to the No.9 Face of the 9th October, preparatory to the construction of the stoppings. After considering the remote possibility of frictional sparking the investigation came to the conclusion hat a much more likely source of ignition was the heating in the No.9 Top Level, and that the general confidence there was misplaced.
To support this conclusion it is necessary at this point to consider the experience with the No.8 Face, the one immediately to the rise side, and which was worked before No.9. This face had no experience of spontaneous combustion during its life. It was abandoned on 9th August 1957 and stopped off on 11th November 1957. Later the stoppings were increased in length by the disposal of waste dirt. In July 1959, samples taken on the No.3 Brow on the return side of both No.8 and No.9 revealed an increase in the carbon monoxide content from about 0.002 to about 0.007 percent. A closer search for the origin of the gas identified it with leakage out of the No.8 Main Level Stopping. Various attempts were made to improve the seal there. The main purpose was to reduce the amount of carbon monoxide on what was the main man-riding road, a concentration, which, although not dangerous, could not be tolerated. The measures adopted, which included the building of a brick wall as a face to the Main Level stopping, were effective in reducing the amount of carbon monoxide reaching the No.3 Brow.
When the No.8 Face was working, it was customary to leave packing about 8 yards thick on the lower side of the Main Level. Between this pack and the coal rib side being formed by the advance of the face, a small airway was left so that air could circulate around the fast end. A continuous small airway of this kind which would in time become inaccessible could not be contemplated in a seam so liable to spontaneous combustion as the Plodder. As a result, this very small airway was cut off periodically by cross drives through the pack about every 40 yards, the abandoned portion behind being sealed.
When No.9 Face advanced later taking out all the coal, these small spaces, and the adjoining pack would be re-exposed, with the result that within a few yards of the left-hand corner of the No.9 Face there would, temporal, be only 8 yards of packing separating No.9 Top Level from what remained of the No.8 Main Level. Despite the thickness of the stoppings at the outbye end of the No.8 Top and Main Levels, it was probable that small leakages of air occurred between No.9 Face and No.8 Face. A small pressure due to the ventilation causing such leakage would be assisted by the gradient and by the high resistance of the outer part of the No.9 Top Level which was the proper path for the air to flow.
Small leakages of this kind are all that are needed to start spontaneous combustion the airflow is insufficient to carry away the heat being generated so the temperature of the material rises continuously. One measurement against such leakage through roadway packs is to raise the floor of the roadways by leaving down part of the face-ripping until the floor level of the roadway being formed is above the roof plane of the coal extracted in working.
This had been along with established practice in certain conditions and could have been carried out in the Top Level of No.9 Face where the Plodder Seam was being worked first over the contiguous Haigh Yard seam. But in the converse case, which is sometimes adopted, of working the Haigh Yard first, the burying packs in this way would be impracticable.
While “digging out” operations were in progress at the heating in No.9 Top Level, those engaged did not notice any movement of the air towards the abandoned No.8 Face, but it was felt that, having found distinctly hot material, and in the absence of any significant amount of carbon monoxide in the immediate atmosphere, the officials should have expected that most of the products of combustion were in fact moving through the pack away from No.9 and into No.8 Face. Such movements would also seem to explain the observed rapid cooling of road surfaces. It was possible that heated material dug out was only part of that actually raised to a high temperature, and that the remainder was still active behind the packing by which the roadway had been restored. The air leakage referred to while feeding more oxygen to the fire, would also, because of its direction of flow, tend to conceal the real conditions from those working there. If some fire continued at this point, it is reasonable to assume that the accumulating firedamp in No.9 Face, once the main stopping was built, would first reach an inflammable or explosive concentration at the higher corner of the face to be ignited there.
Although new packing had been inserted between any continuing fire in No.8 and No.9 Top Level, it would not be flameproof, and it is conceivable that the ignition of an explosive mixture first occurred in No.8 Face and was propagated through the new packing into a larger accumulation of firedamp then present in No.9.
There as other, and perhaps more reliable evidence that the signs first observed by Deputy Hodgson on the 4th October were indicative of only a fringe of what might have been heating of a fairly high intensity somewhere on the lower side of the No.8 Main Level. I have already referred to the detection in July last of excessive amounts of carbon monoxide from the stopping on the No.8 Main Level.
While the leakage might have been due to expansion of residual gas under falling barometric pressure, it did in fact occur during periods of very sable pressure, and therefore was more likely to have been caused by leakage coming in from No.9 Face under the influence of ventilating pressure and some buoyancy. Indeed it would be seen that the progressive advance of No.9 Face was to some degree unsealing No.8 or at least aggravating the leakage of air, and I can imagine a similarly progressive tendency to self-heating along the right-hand side of the No.8 Main Level. If heating did occur it would probably be stifled by the consolidation of the packing as No.9 Face advanced, and so I envisage the greatest intensity of heat or tendency to self-heating would be just behind the No.9 Face. Once this face stopped, leakage would continue for some time at one place and the heating would grow in intensity until its effects began to be noticed within the No.9 Face and were, of course, eventually detected by Hodgson on the 4th October.
There was further support for this view, but for this purpose from the work that had been done on the analysis of the constituent gases in mine atmospheres, which has been long established as a reliable indication of the rate of oxidation (and self-heating) of coal substance.
With the oxidation of coal, a variable amount of carbon dioxide and carbon monoxide is produced. With the oxidation of coal at normal temperatures, a very small quantity of these gases is produced in relation to the amount of oxygen absorbed. However, Mr. T.F. Winmill and Mr. J. I. Graham working together as long age as 1915 found that the proportion of carbon monoxide varies more particularly with the temperature and this gas is readily and conveniently determined with modern apparatus in very small proportions, down to a few parts per million. Accordingly, spontaneous heating in the coal substance is always associated with a rise in the ratio of carbon monoxide produced to oxygen absorbed usually expressed as a percentage, in the formula:- Carbon monoxide produced/Oxygen absorbed x 100, and Graham suggested this ratio as an indicator to be used in the early detection of heating. Its value is maintained even when the temperature continues to rise and actual fire results, though in open workings, with the constant examination, other than the obvious signs will then have become evident. Since there is some very small amount of carbon monoxide produced with normal oxidation, the ratio is calculated will have a normal value for every seam or group of workings, or for a mine depending upon where the carbon monoxide present and the oxygen loss, respectively, are assessed. The indication of spontaneous heating lies in the rise of this ratio above what is known to be the normal value. From the experience of sampling over several years I am advised that the normal value of this ratio for the Plodder Seam at Bickershaw was 0.4 to 0.5 percent.
There were increased levels of CO in the No.3 Brow which was later identified with an increase in the expulsion of this gas from behind the stoppings on the No.8 face. A sampling of the atmosphere from inside these stoppings was also continued and the samples collected during the period 5th to 10th October 1959 were typical of those collected earlier in August and September.
At first glance, the air content of these respective groups of samples might be accepted as not being abnormal from a sealed area presuming some leakage of air through the Main Level stopping which was the original intake. However, the general consumption of the samples does not support this. Theses from the Top Level show a low carbon monoxide/oxygen ratio and a high carbon dioxide content and therefore no evidence of heating but rather vitiation from ordinary oxidation.
However, the samples form behind the Main Level stopping give a high carbon monoxide content (air-free) and a high carbon monoxide/oxygen ratio and thus are typical of an atmosphere on the return side of a serious heating. In the absence of any known heating near the No.8 Main Level stopping itself (a possibility which cannot be ruled out), the atmosphere behind this stopping must be related to the known heating where No.8 and No.9 Faces joined. The continence of an abnormally high carbon monoxide/oxygen ratio from the samples collected from behind No.8 Main Level stopping after the heating in the left side of the No.9 Top Level had been dug out should have awakened some doubt of the complete efficacy of the measures there taken
There appeared to be some little doubt of the reliability of the carbon monoxide/oxygen ratio when applied to stopped off areas, and this feature offers application is worthy of further investigation. It was reasonable to expect that the manager’s advisers, and in particular the Area Scientific Service, who was responsible for providing him with the analyses of the samples of atmosphere, might have shown more concern, and made a wider investigation of the series of results from No.8.
In justice to the management of Bickershaw, the investigation recorded that members of my staff, Mr. J. Lane, H.M. Senior District Inspector, and Mr. R. N. Foster H.M. District Inspector, were in touch with the developments during the few days preceding the explosion. In fact, Mr. Foster visited the No.9 stoppings during the morning of the day of the explosion.
These two Inspectors from their own knowledge and observation shared the confidence of the management that no active fire was being sealed off, but at that time they were not aware of the character of the range of samples taken from behind No.8 stopping which was significant evidence of fire more deep-seated in No.8 Face than was suspected. However, in the light of subsequent and closer examination of the nature of these analyses from No.8 Stoppings, it was concluded that fire existed in No.8 Main Level, or near it. The fire might not have been of a large extent but was probably of a high intensity. Whether this was part of the fire found in No.9 Left Hand or another was conjectural.
In sealing off active fire there is a code of General Regulations first made in 1933 and now re-enacted under the Mines and Quarries Act 1954 as Coal and Other Mines (Fire Rescue) Regulations, 1956. Among other things, these Regulations require the withdrawal of all persons from a mine during the process of sealing off or damming off except those necessary to the work of building stoppings. In addition to these Regulations, there is an accepted code of safe practice within the coal mining industry based on a large amount of experience.
In 1944 this experience was embodied in a memorandum prepared by a Committee appointed by the Council of the Institution of the mining engineers on “Sealing off Fires Underground”. This memorandum, among other matters, dealt with the position leading up to the final sealing of stoppings already erected in part and on sealing being completed, advised the withdrawal of all persons during a period of twenty-four hours.
This time interval could only be an arbitrary one, but from the accumulated experience of the Committee, it was felt that if in any circumstances an explosion inside the stoppings was to occur, it would come about well within that period. If Mr. Lawson, or the other members of the executive management at Bickershaw, had a remote possibility of fire continuing in the region of the No.9 Left-Hand side of No.8 Right-Hand side, the final sealing of the stoppings on the 10th October would have been conducted in accordance with the recommendations of the memorandum, in which case on one would have been at risk when the explosion occurred.
Another factor that must have contributed to the rate at which firedamp collected behind the stoppings on the No.9 roadways was the fall in barometric pressure which began about 1 p.m. on Friday the 9th October after an unusually long period of stable pressure which accompanied the summer and autumn months in 1959. The fall of pressure continued into the 10th of October, the day of the explosion. The maximum rate of fall was one of 2 millibars per hour during the four hours 12 noon to 4 p.m. This rate of fall though not abnormal is quite appreciable and would have a significant effect in producing an inflammable mixture in the sealed area at an earlier stage after the stoppings had been finally plugged.
Bickershaw Colliery, amongst others in the North West Division, receives warnings from the Meteorological Office of approaching severe barometric depressions, a service initiated by the National Coal Board as a measure of assistance to these in charge of gassy seams. t was confirmed that a signal was sent out by the Met Officer of an expected rate of depression and was received at the Colliery about 3 p.m. on the 10th October. Before the sealing of No.9 and afterwards this knowledge by the officials of a sharp fall of barometric pressure would not be expected, under the circumstances to create any great anxiety in their minds about the conditions in the No.9 area, unless they knew, or were suspicious, that material at high temperature was being sealed off.
Without this knowledge or suspicion, the precautions to be taken would consist simply of the vigilance towards the appearance of inflammable of noxious gases near the stoppings at which men were working. The evidence I have heard is to the effect that the deceased officials and the trained rescue men who were with them had been constantly on the watch for such gases.
In the circumstances of an explosion behind the stoppings which were largely left intact, and outside of which there was no flame was seen to pass by those who survived It was not certain what part was played by coal dust in carrying the explosion towards the stoppings on No.9 roadways. The No.9 Main Level had been a coal transport road during the working period which ended on 14th. August 1959 and the manager, Mr. Lawson, stated that until that date a stone dust barrier erected in accordance with the National Coal Board internal directive was in position about 200 yards from the face.
However, Mr. Lawson recollects that after production ceased this barrier was removed so that the fittings could be used elsewhere in a productive unit. The volatile content of the Plodder Seam is 38.1 percent which to comply with the Coal Mines (Precautions against Inflammable Dust) Regulations 1956, required the maintenance of at least 75 percent incombustible matter in a mixture with the roadway dust when sampled in the prescribed maker. Samples of roadway dust were collected from No.9 Main Level and No.9 top Level in July 1959.
The records at the colliery show that the lowest portion of incombustible matter found in the Main Level was 91.5% and in the Top Level 89%. These samples were collected some four weeks before coal production and transport ceased and therefore do not necessarily represent the conditions at the time of the explosion. It was stated by the manager that it was unlikely that any further inert dust treatment had been given to these roads after coal winning stopped on the 14th of August since the main production of coal dust would then cease.
It was concluded that the explosion that occurred on the 10th. October was mainly one of firedamp which inevitably collected on the No.9 Face and in the Main and Top Levels when the stoppings on these latter two roads were finally plugged and sealed. The firedamp would probably reach inflammable proportion first in the top corner on No.9 Face adjacent to where spontaneous combustion persisted. Firedamp was ignited thereby some heating material lying possibly within the old right-hand packing of No.8 Face just beyond the reach of the excavation carried out at that point on 4th and 6th October.
The danger of explosion following sealing was accentuated by the rapid fall in barometric pressure experienced before and during sealing. Having in mind the character of the No.9 Main Level as a coal transport road, it was possible that coal dust played some part in propagating the explosion towards in the Main Level stopping.
The exemplary behaviour of all persons in the neighbourhood of the stoppings when the explosion occurred. Everyone acted with immediate concern for the safety of the five men near the Main Level stopping and in particular, the act of putting the roadway conveyor into its normal running direction (top belt moving outbye) was a resourceful move made in the hope that some survivor would not be too disabled to use this means of getting to safety. That it was unavailing does not detach from the inspiration which prompted it.
Two members of the Permanent Rescue Corps, Mr. W. Sturgeon and Mr. K. Shaw were commented on. With the support of their Brigade companions, they made the necessarily brief but observant examinations of the two stoppings after the explosion. They, above all, from their tracing and experience, would be aware of the danger of a second explosion, and their subsequent reports of the condition of the stoppings and the information that no fire existed in the open roads outside provided a valuable and comforting reassurance to all concerned with the remaining operation of the sealing off the Plodder Seam.
The following recommendations were made:
- I understand that the Council for the Institution of Mining Engineers have adopted a small Committee to revise the Memorandum “Sealing Off Fires Underground” originally published in 1944 and referred to in Paragraph 46 of this report. Although the point may not strictly be within the terms of reference of this Committee, I think it should consider, concurrently with other related matters, the value to be attached to the relationship between carbon monoxide produced and oxygen absorbed, and indeed any other relationship between constituent gases found in samples of the atmosphere taken from behind stoppings as an indication of continuing fire or of the progress of spontaneous combustion.
- Where longwall working in seams liable to spontaneous combustion it is the practice for successively worked faces to strip the goaf edges of previous workings already stopped off, further measures should be considered with a view to minimizing leakage between a working area and sealed off one. In this connection, the already common practice of burying packs should be extended. in addition, sand packing should be inserted alongside coal ribs, especially where these will be subsequently taken out by a succeeding working.
- In all cases, the time which elapses between a working face ceasing production and its final isolation with explosion-proof stoppings should be as short as possible compatible with the recovery of valuable machinery and tools.
- Since the danger of an inflammable atmosphere can arise in any area or workings to be sealed as soon as the ventilation is reduced in amount by the beginning ion the stoppings, their completion to an explosion-proof condition should be effected as quickly as possible whether a fire is present or not. Consequently in seams liable to spontaneous combustion I recommend that sites for stoppings should be selected and some preparatory work was done while the unit is still in production. In fact in some seams where spontaneous heating if frequent such preparatory work has been the traditional practice.
REFERENCES
The report of the causes and the circumstances attending the explosion which occurred at the Bickershaw Colliery, Lancashire on the 12th November 1959 by Mr. R.H. Clough. C.D. ??
Information supplied by Ian Winstanley and the Coal Mining History Resource Centre.
Return to previous page