Six Bells Colliery, Monmouthshire. Disaster, 28th. June 1960.
I'm indebted to Joe Stocks for sending me the Inquiry report by
T.A. Rogers, C.B.E., M.I. Min.E. H.M. Chief Inspector of Mines and Quarries.
It is the only source of information used on this web page.
The disaster was caused by an ignition of firedamp approximately 10:45am near the face of the intake airway/loader-gate of O.10 conveyor face in W District of the Old Coal Seam.
Coal-dust was raised and ignited and the explosion spread almost throughout the district.
The initially ignition of firedamp was believed to have been by an incendive spark caused by the impact of quartzitic stone falling from the roadway roof near the face of the ripping lips onto a steel canopy used to protect the roadway conveyor during blasting operations.
Forty-five men were killed. Lethal concentrations of carbon monoxide gas were present which suggested the men lost consciousness rapidly and death occurred within minutes.
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Ivor James Baiton aged 48, cutterman.
Daniel James Bancroft aged 46, collier on panzer.
Robert Charles Brown aged 35, roof control officer.
Frank Cooper aged 44, supplies man.
Joseph Corbett aged 50, haulier.
Thomas George Crandon aged 46, repairer.
Walter Thomas Davies aged 34, borer.
Royden James Edwards aged 27, repairer.
Percy Gordon Elsey aged 52, repairer.
Albert John Evans aged 34, packer.
Leonard Keith Frampton aged 29, collier.
Albert Gardner aged 59, assistant cutterman.
George Goldspink aged 37, repairer.
Clive Alan Griffiths aged 18, prop checker.
Vernon Alexander Griffiths aged 33, deputy.
Earnest Victor Harding aged 51, deputy.
Idris Jones aged 57, packer.
John Percival Jones aged 56, repairer.
Joseph John King aged 56, packer.
Dennis Edmund Lane, aged 19, wireman.
George Henry Luffman aged 55, general worker.
Telford Cecil Mapp aged 42, general worker.
Herbert Amos Mayberry aged 55, dumper.
William John Morden aged 52, engine driver.
Sidney Moore aged 54, repairer.
Colin Malcolm Donald Morgan aged 26, repairer.
Colin Reginald Morgan aged 22, assistant repairer.
Ray Martin Morgan aged 44, repairer.
Islwyn Morris aged 44, deputy.
Anthony Verdun Partridge aged 20, assistant borer.
William Henry Partridge age 45, borer.
Trevor Paul aged 25, assistant repairer.
Wilfred Alfred Charles Phipps aged 60, cutterman.
Albert George Pinkett aged 45, collier.
Frederick Rees aged 37, fitter.
Mansel Reynolds aged 21, measurer.
William Glyn Reynolds aged 21, assistant repairer.
Wilfred Hughes Thomas aged 57, repairer.
Arthur Waters aged 37, general worker.
Phillip John Watkins aged 53, engine driver.
Wilfred Weston aged 47, water infuser on panzer.
Frederick White aged 58, under-manager.
William Burdon Whittingham aged 55, assistant repairer.
Richard John Williams aged 51, general worker.
John Woosnam aged 24, fitter.
Three men who were on the fringe of the explosion survived, and only had minor injuries.
M. Purnell a linesman,
H.J. Legge a fitter.
C.J. Lewis a fitter.
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Public Inquiry.
A Public Inquiry began in the No. 2 Court of the Civic Centre, Newport, 19th. September 1960 and finished on the 28th. September 1960.
Parties present: -
Ministry of Power.
Mr. C. Leigh, M.I.Min.E., H.M. Divisional Inspector of Mines and Quarries, South Western Division.
Dr. E. M. Guenault, Deputy Director of the Safety in Mines Research Establishment.
National Coal Board.
Mr. G.G. Baker, Q.C.
Mr. A. G. Davies, Barrister.
National Union of Mineworkers, South Wales Area.
Mr. E. Ryder Richardson, Q.C.
Mr. I.B. Fife, Barrister.
The National Executive Committee.
By Mr. W. Whitehead, President of the South Wales Area.
National Association of Colliery Overmen, Deputies and Shotfirers.
Mr. P. Wien, Barrister.
National Association of Colliery Managers and the British Association of Colliery Management.
Sir Andrew Bryan, D.Sc., LLD., R.R.S.E., M.I.Min.E.
Seventy-three witness gave evidence.
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Information about the Colliery.
Six Bells formerly known as Arrael Nos. 4 and 5 in the No. 6 area, National Coal Board's South Western Division.
Six Bells is 12 miles north of Newport, Monmouthshire.
The colliery had three shafts, one Vivian Pit, a downcast/man-riding shaft was nearly half a mile north, and was once part of another mine; it's existence is not material to the circumstances of the accident.
The two other shafts were at Six Bells both used for winding men, coal and materials.
No. 4 the upcast shaft had an electrically driven exhausting fan, capacity of 280,000 cubic feet per minute at 4:6 inches of water gauge.
No.5 was the downcast shaft.
1,213 men worked underground with 239 on the surface.
Output was about 1,800 tons of saleable coal a day, about 830 tons from the Old Coal Seam.
The Colliery was always a safety lamp mine with 1,450 electric cap lamps, 85 flame lamps, which were used by workmen as firedamp detectors, 79 internal relighter flame lamps for use by the officials.
The Under-manager of No. 5 pit (this included W District) was Mr. F. White. He was killed in the explosion.
Colliery Manager was Mr. V. Luther.
Group Manager was Mr. R. Williams.
Area Production Manager was Mr. A.E. Hiscox.
Area General Manager was Mr. L. Walker.
The Old Coal Seam.
This was the lowest worked at 352 yards deep at the Six Bells shaft. The average depth of W District was 550 yards. The increase due to both seam dip and surface rise.
Seam thickness averaged four feet nine inches with a middle dirt band a few inches thick.
The Meadow Vein coal was 22 yards above but had not been worked in this area.
Strata between the two seams were mainly strong 'clift' or shale.
Some five feet above the Old Coal Seam there often occurred a bed of quartzitic sandstone about one foot three inches thick.
Also a 'rider' coal about one foot six inches thick, about twenty- five feet above the Old Coal Seam.
Working faces in W District were indentified by a number prefixed by the letter 'O'.
Three single-unit advancing longwall faces were situated between one and one and a quarter miles from the shafts. Heading north towards disused workings of Marine Colliery.
O.10 unit had gobs from previously worked faces on its right hand side.
O.12's was beginning to skirt the left side of O.10's unit.
O.18's had solid coal on both sides.
Roadways rose slightly towards the faces, which in turn rose slightly from west to east.
O.10 and O.18 units were normal production units.
O.12's was a standby face, coal was filled two weeks out of three on the morning shift. In the third week coal was filled on the afternoon shift.
O.10's was 103 yards long, advancing at a rate of about 12 yards a month to within 55 yards of Marine Colliery old workings.
Coal was cut by a machine mounted on an armoured conveyor. Driven by compressed air.
Hydraulic props and link bars a meter long were used in a "prop free front" system of support. Roadside packs were eight yards wide the waste between was completely caved.
The intake/loading gate was supported by steel arches covered by wood lagging. The arches were 12 feet wide by 10 feet high. Six feet of ripping was removed to achieve this height.
O.9's old intake was used as O.10's supply road, this was being reconditioned as the face advanced.
Shots were fired in the coal and in the stone of the intake face ripping.
O.18's face was 96 yards long, advancing at about 27 yards a month.
Coal was cut near the floor by a machine to a depth of 4 feet six inches. Then filled by hand onto a belt conveyor. Machines were driven by compressed air.
The roof was supported by adjustable friction-type props and linked bars four feet six inches long.
The waste had been completely caved until roof bad conditions were experienced. In May 1960 strip packing was introduced, the packs were four yards wide and the wastes nine yards.
The intake road was supported by 12 feet by 10 feet arches for the first 200 yards, then with 8 feet by 7 feet arches for the last 40 yards.
The return was supported by 10 feet arches, the height being obtained by ripping mainly in the roof.
Shots were fired in coal and, except for the intake, in stone.
O.12's standby face was 118 yards long, coal was worked and filled by hand onto an electrically driven scraper chain conveyor.
The face had advanced 20 yards, 10 yards in the six months before the explosion. It was last worked one shift before the explosion on 8th. June 1960.
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Transport of coal and supplies.
Coal was transported from the face conveyors onto stage loaders then onto semi-troughed belt conveyors, which loaded onto two 30-inch belt trunk conveyors in tandem on the main intake.
These were all electrically driven.
A tram loading point was on the double parting near old O.1's intake.
O.18's supplies were transported on trams by a system of compressed air haulages from the double parting through O.7's crosscut to the main return and then to the face of the supply gate.
O.10's and O.12's supplies were taken by trams through O.7's crosscut to the main return, then back through O.2's crosscut to the main intake. The supplies were off-loaded there and manhandled. They were drawn up O.10's supply gate on a single tram hauled by a compressed air haulage engine that was sited near the face.
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Ventilation.
About 5,000 cubic feet of air per minute entered O.10's face from the loader gate. 1,500 cubic feet of air per minute of controlled leakage air passed along the supply gate.
The firedamp content 30 feet on the return side of the face (the statuary measuring point), averaged about 0.25 percent.
About 9,500 cubic feet of air per minute reached O.18's face and the firedamp average 30 feet outbye from the face averaged 0.8 percent.
No express provision was made to deflect air into O.12's face, although a measurement taken after the explosion showed 3,300 cubic feet of air per minute at the lower end of the face. The ventilation naturally took this course; to this extent the ventilation of O18's face was in series with O.12's.
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General mining experiences.
The only major difficulty in working O.10's unit was from a large roof cavity on the intake, near two parallel faults some 170 yards from the main intake.
The cavity began at the roadhead and extended as the face advanced until it was about 30 feet long by 20 to 30 feet high.
Arches were set beneath the cavity; they were covered by lagging timber and some debris.
It is probable that by the time of the explosion a good thickness of stone had fallen onto the arches and its covering.
Firedamp had apparently accumulated above the debris and was sometimes found at the face ripping until, but not after, 9th. May 1960. At the time of the explosion it was not considered necessary to use a brattice sheet at the face ripping. Small quantities of firedamp were frequently found elsewhere in the unit.
Firedamp was sometimes found in small amounts at O.12's loadergate face ripping.
Firedamp was often found in O.18's unit, most frequently at the intake roadhead face ripping: sometimes shots could not be fired.
An investigation by the area ventilation engineer R.W. Simpson, in December 1959, resulted it a venturi type air blower being installed at the ripping.
This did not completely solve the problem: in May 1960, the thickness of the roof ripping was reduced to about 3 feet by taking up some of the floor, and reducing the road height by using eight feet arches.
The Manager prohibited shot-firing at the ripping and arranged for methanometer surveys of the unit on a daily basis along with reports of the results.
A venturi system was also installed in the face ripping of the return roadhead.
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Shifts before the explosion.
Afternoon shift 27th. June 1960.
Normal coal filling operations on O.10's. Supervised by overman W. Doel and deputy J.D. McDonald.
R. Hall a deputy acting as a shot-firer, assisted by K. Baker, collier, fired 30 shots in the coal.
Neither Hall nor the overman found any firedamp when they tested the waste at the return end of the face before shots were fired.
McDonald on his mid-shift inspection found small feeders of firedamp in O.10's and O.9's returns and in O.12's loader gate.
During his pre-night shift inspection he found the same small feeders.
T.G. Morgan the overman in charge of O.18's said, trouble with conveyors resulted in coal filling starting late, and the cut was not cleared. Deputy D.E. Price, found firedamp during both his mid-shift and pre-night shift inspections, at the face ripping of the return, at the face ripping of the intake and at two places on the face.
Late in the shift it was reported to Price that a coupling on the face conveyor motor had been sparking, when he reached the place this had been attended to by the fitter, and he was satisfied the problem had been rectified.
Night shift 27th. 28th. June 1960.
O.10's.
Only ripping and repair work was being done.
R.H. Law was the deputy in charge.
During his mid-shift inspection he found small quantities of firedamp in the returns of O.9's and O.10's. His pre-day shift inspection also showed slight indications of firedamp in the return end of the waste, and in the return of O.10's unit, in O.9's return rippings and in a cavity farther outbye.
He did not find firedamp in O.10's intake rippings during either of his inspections.
At approximately 3:00am. E. Boots, shot-firer, assisted by J.H. Evans, fired a round of 4 shots with a six shot exploded in O.10's intake face rippings.
He said he tested for firedamp, examined the holes with a break detector and charged each hole with two four-ounce cartridges of Unigex explosive. Evans filled sufficient stemming bags with stone-dust. Boots did not put a filled bag at the back of any hole before charging. He fired the round, examined the rippings for firedamp and pulled down some loose stone. Law was not present during shot-firing operations, but during his inspection later noticed some bed separation at the face of the ripping.
He noticed the fore-pole supports were not advanced but considered it was safe to leave this until the day shift.
O.18's.
The deputy was W.C. Nash, he found firedamp during his pre-day shift inspection in the intake ripping and he replaced a brattice sheet there.
No shotfiring took place in this unit on the night shift.
W.V. Jenkins and A. Mathews, fitters, were putting a two-inch compressed air supply pipe through an existing hole in O.9's undercast. They noticed an arch girder on the face side of the undercast had shifted slightly and a small amount of debris had fallen. They thought there was no immediate danger of further falls.
The compressed air was twice cut off from the whole district as Jenkins also repaired a tapping gland on an eight-inch compressed air supply pipe. During these periods, from 11:30pm to 12:15am, and 5:30am to 6:15am, the Venturi appliance on O.18's could not function.
Day shift 28th. June 1960.
The day shift descended the mine between 6:00am and 6:30am.
What work they were deployed to that shift is not known, but the Manager said he would have expected: -
O.10's face, five men including the deputy.
O.18's.
Intake face rippings, three or four men.
Return end of face, two men working the coal-cutting machine.
Return airway, a maximum of six supply men.
Return just outbye of the crosscut near O.18's, a borer and his assistant.
The remainder of the men, who would normally have been advancing packs, withdrawing supports and advancing the face conveyor. Should have been cleaning up along the main loader belts, which had been reported as, getting into a dirty state.
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The Explosion and Recovery.
At about 10:45am M. Purnell, a linesman, was working with D. Lane putting up a signal line near the electric haulage engine about 25 yards inbye of the entrance to the old T intake.
Lane was about 10 yards inbye of Purnell when there was a lot of noise and dust. Purnell fell on the engine and Lane was blown past him.
Purnell had no idea what had happened, he got up then found Lane apparently dead.
Purnell made his way to the pit bottom, feeling along the pipe ranges because the air was thick with dust.
Two fitters, H.J. Legge and C.J. Lewis, were eating food by the transformers in the mouth of the old T intake. They heard a sound like a compressed air pipe bursting.
There was a great deal of dust in the air and they lost contact with each other. They both made for the pit bottom as best they could.
Legge thought a transformer had blown up and on his way outbye he telephoned the pit bottom.
Shortly afterwards he met S. Holland a deputy who was responsible for the inspection of airways, and W. Coleman, an engineer, who were investigating what had happened. He told them of his experience.
Holland and Coleman were coming outbye from an old district when they met a cloud of dust. They thought a compressed air supply pipe had broken and they made their way to the downcast pit bottom.
The dust cloud was also observed at both shafts and someone telephoned the surface.
The manager phoned an instruction for Holland to investigate, he and Coleman went inbye along the main intake towards W District.
They met some men going about their normal work and were informed that one man nearby was feeling ill. Holland arranged for him to be taken out of the pit. He didn't speak to the man but realised later that it must have been Lewis.
Holland and Coleman later met Legge, who told them about the happenings at old T transformers.
They went to these transformers but found them undamaged, they returned to the main intake and continued inbye.
A few yards past the junction with old T intake they saw a body, which must have been Lane.
At the double parting the air was so thick of dust they concluded that there must have been an explosion.
Unable to contact the pit bottom by telephone Holland sent Coleman out to report to the manager, he went on alone.
Just inbye of the airbridge at O.7's he found a fall of ground almost blocking the main intake and he decided to retreat.
When travelling outbye he noticed one or two separation doors in the mouth of old T return were damaged. The other door was open and he closed it; then noticed a considerable increase in the quantity of air passing down the main intake.
Holland continued outbye where he met the manager, and the area general manager, who happened to be visiting the colliery.
He told them what he had found and the manager issued instructions for all men to be withdrawn from the pit, and put the emergency procedure into operation.
All three returned to the surface to study the plans of the mine, and to determine what action was necessary knowing that access to W District was blocked by the roof fall.
Shortly afterwards the manager and Holland went back underground with a canary, on their way inbye they met H. Silverthorne, an overman. They all went to the fall where they met P.J. McLaughlin, another overman who was also the captain of the colliery rescue team.
They found a number of men; one was B. Rees, a collier in No. 4 Pit, who was chairman of the colliery lodge of the National Union of Mineworkers.
Some of the men had found two doors in O.7's crosscut destroyed. They fixed up a temporary door to help restore the ventilation flow.
The manager instructed everyone to leave the pit except Holland, Silverthorne and McLaughlin. Then they went through O.7's crosscut into the main return, where they tested for firedamp and found up to two percent in the general body of air.
15 yards inbye of the junction of O.9's return, McLaughlin noticed the canary had died. They decided to retreat, they went back to the fall in the main intake and started to make a hole over it. They had just done this when the rescue teams began to arrive.
Rescue brigade men from Porth Central Rescue Station and Six Bells Colliery went down the pit soon after 1:00pm. Under the supervision of the Superintendent of Crumlin Rescue Station.
They set up a fresh air base then began exploratory work; later two other teams supported them.
Initially the hole made over the fall was not large enough for access by men wearing breathing apparatus, so the first explorations were made via O.7's crosscut and the main return.
One team got half way along O.18's face before the 'life' of their breathing apparatus was expiring and they had to retire.
They found a number of bodies and observed that the doors on the crosscut near O.18's unit had been blown towards the return.
Another team went into O.9's return but there was a fall of roof just inbye of O.9 undercast.
The two teams returned and gave their reports, by this time the hole over the fall in the main intake had been enlarged.
Teams made systematic explorations of all roads and faces, they returned and reported that air was stagnant and there were no survivors.
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The investigation.
Preliminary examination of the affected area failed to disclose the cause of the ignition, and indicated that it would be difficult to find the point of origin of the explosion.
Microscopic examination of over 500 specimens of dust and fibrous material indicated the flame had swept through 3,000 yards of roadway and each face with the exception of O.10.
Flame had traversed the main intake road, both roads serving O.10, most of the old O.9's return, the intake of O.18's and its return for 30 yards outbye from the face.
The main return was affected only locally by flame through the crosscuts.
There were signs of prolonged burning of firedamp in two lengths of roadways, for 70 yards outbye from O.10's intake roadhead, and for about 25 yards outbye from O.18's return roadhead.
The explosion was not a violent one; indications of blast were not very prominent.
Painstaking investigations revealed: -
On the main intake there were signs pointing in both directions from near the junction with O.10's intake.
The inbye indications persisted to and along O.18's intake and continued along the face.
Signs in O.10's intake, on the whole pointed outbye from the face.
In O.10's supply gate, the doors at the entrance were blown inbye towards the face, but there were signs of blast in both directions at the junction of the face and roadway.
In the restricted area of old O.9's face there were strong signs of blast towards the return.
The brickwork sides of O.9's undercast were blown in directions away from the main intake.
The doors in O.2's crosscut, in O.7's crosscut and in the crosscut near O.18's unit were all blown towards the return airways.
Specimens of coked dust indicated the directions of flame. These indications were generally consistent with the indications of the blast. Minor and local contra-indications were not unusual; there were clear signs that the flame entered both ends of O.12's face.
Coked dust depositions found in O.10's supply road indicated the flame travelled from the main intake to old O.9's face and along it to O.9's return where it died out at about 200 yards from the face.
Ventilation tests.
The amount of ventilation in and near the faces was greatly reduced by short-circuiting the main the main intake and return airways and, in O.10's unit, by blocking the old O.9's return.
Nothing significant emerged. The firedamp ceiling in the cavity on O.10's intake lowered a little; a thin roof layer was detected by probe and methanometer for some distance inbye the firedamp dispersed into the general body of air long before it reached the face.
A careful watch was maintained, especially at times when the barometric pressure was falling, close to the inaccessible connection between the old O.9 main gate and the Marine gob. There was no indication of firedamp being given off.
Safety Lamps.
Forty-eight electric cap lamps and eight flame lamps found in the affected area were sent to the Safety in Mines Research Establishment for examination.
Twenty-nine of the cap lamps were undamaged; the explosion damaged the others.
Four of the flame lamps were undamaged and three slightly damaged but shown to be still safe. One was badly damaged but as this lamp was found on the main intake, the damaged was considered to be consequential.
Contraband.
A police constable examined clothing of the victims at the surface and found an unsmoked cigarette.
A.S. Jones, H.M. Inspector of Mines and Quarries found two live matches in a haversack underground.
J.T. Thirlaway, area scientist, during district inspections, examined a polythene bottle and found inside it a plastic bag tied to the stopper by thread.
L.G. Fear, H.M. Senior Inspector of Mines and Quarries, and members of his staff made further extensive searches for contraband in the district but found nothing else.
Roadway dust samples.
Examination of the colliery records showed the procedure for taking and testing roadway dust samples before the explosion was in order, except that no samples were taken in December 1959 or April 1960.
No explanation was given for December's omission, but the man responsible for taking samples in April said his daily preoccupation with the ventilation of O.18's unit prevented him from doing it.
Forty-four samples were taken on 21st. June, a week before the explosion. Forty-one of these contained over 80 percent of incombustible matter.
Three other samples, all taken near the main loading point, contained, 57, 70, and 75.6 percent of incombustible matter.
The volatile matter of the coal worked was less than 25 percent. The management could, if they had they notified the H.M. Inspectorate, have established 60 as the minimum percentage of incombustible matter, which was required to be maintained.
This had not been done, so the minimum percentage required by regulation of 75 automatically applied.
C.A. Bilton, H.M. Inspector of Mines And Quarries, collected six samples on the 17th. May 1960. Two just inbye the main loading point, two just inbye the transfer point of O.18's gate belt to the trunk belt and two in O.18's return immediately outbye the roundhead.
Analysis of the samples showed, four contained more than 75 percent of incombustible matter. The other two contained more than 70 percent but less than 75 percent. H.M. Senior District Inspector informed the management of this in correspondence.
He was assured the zones concerned had been retreated, and results from re-sampling were satisfactory.
Post explosion roadway dust sampling and analysis showed the majority of samples contained less than 75 percent of incombustible matter.
Of 64 samples taken in conveyor roads 29 contained more than 60 percent but less than 75 percent of incombustible matter.
29 contained less than 60 percent of incombustible matter.
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Mechanical apparatus.
K.S. Worthington, H.M. Inspector of Mechanical Engineering, examined the mechanical apparatus in W. District, and the air compressing machinery, on the surface.
The standard of installation and maintenance was generally satisfactory.
There were some minor defects but none contributed to the explosion.
A hole in a compressed air pipe had been repaired using paper and hemp rope; this could have cause a fire.
A wooden plug was driven into a hole in the compressed air supply main about 40 yards from the roadhead of O.10's intake. The plug showed signs of heat; believed to have been caused by the explosion.
Three compressed air pipe joints made with rubber rings were found to be blowing badly on O.12's face. Laboratory examinations showed no sign of frictional heating.
O.10's stage-loader driving motor, about 30 yards from the face of the intake, was fitted with an aluminium alloy fan and cowl. The cowl had been fractured, but cracks did not seem to be freshly produced. Nor were there any recently made indentations or abrasions. Some steel wires of the mesh guard covering the air inlet in the cowl had at some time fouled the roots of the fan blades. The rubbed surfaces were not new.
The fan was free running, without any end play on the motor shaft, which might have allowed the fan to rub against the wires or other surface.
O.10's supply gate haulage engine was found with the throttle valve partly open, the brake off and reverse gear engaged.
The rope 'lead' was underneath the drum instead of above as was normal.
In O.10's supply gate an empty tram was found between the doors, the haulage rope attached to it was very slack. A "barhook" (backstay) was attached to and beneath the tram as though it had been over-ridden.
It was suggested that the haulage engine might have been running in reverse gear when the explosion occurred and continued to do so until the air pressure fell due to a breakage of pipes caused by the explosion.
Tests after the explosion showed that when the engine was left running after the tram reached the outbye end of the road the spare rope stayed slack on the drum until it was caught up and coiled in the opposite direction.
Old indentations on a girder of the haulage framework indicated that at some time the rope had coiled beneath the drum.
Evidence that the engine might have been running was tenuous as the throttle lever might have been moved during the explosion, or accidentally after it.
The examiners were satisfied that incendive sparks would not have been produced.
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Electrical Apparatus.
A.L. Alexander, H.M. Electrical Inspector of Mines and Quarries and Chief Testing Officer of the Safety in Mines Research Establishment, inspected all the electrical apparatus in position, and 95 items were sent to the Safety in Mines Research Establishment for further critical examinations and tests.
The apparatus was found to comply with the certified designs. Apart from minor defects was well maintained.
Every flameproof enclosure was tested twice to find whether, under the most stringent conditions, an explosion of firedamp in air within it would ignite a surrounding inflammable mixture of firedamp in air.
The external inflammable atmosphere was not ignited during any of the 124 tests made.
Telephone and signalling appliances were tested for intrinsic safety in methane/air mixtures.
The explosion damaged some items, but tests showed that an adequate margin of safety had existed under working conditions.
Remote control circuits associated with eight gate end switches controlling the conveyor motors that were certified as intrinsically safe in 1939. When tested by a more modern method, were capable of igniting methane. In seven of the circuits used, the remote control cables were intact and the remote control enclosures were proved to be flameproof.
In the remaining circuit, the remote control switch housings were flameproof but the connecting cable was damaged. The damage was such that sparking could not have occurred.
A single-shot exploder found in O.18's return was tested and it conformed to its approval specification.
The wire-armoured roadway cables were examined underground. They were tested at a voltage considerably higher than the normal working voltage. No defects liable to cause open sparking were found.
All flexible cables in use were examined at the surface; these were again tested at a considerably higher voltage than normal working voltage. No defects liable to cause open sparking were found.
Tests on two "Venturi" tubes to determine if they could have accumulated an electrostatic charge sufficient to cause an ignition were carried out.
The tests were made in conditions far more conducive to the development of such a charge than likely the pit, but the maximum charges developed were not capable of igniting firedamp.
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The cause of the explosion.
F.J. Hartwell, a Senior Principal Scientific Officer of the Safety in Mines Research Establishment, said the indications of the directions of blast and flame suggested to him that the explosion started in the vicinity of O.10 intake roadhead.
There appeared to be a zone there of small disturbance in which little dust was raised but relatively prolonged burning of rich firedamp had occurred.
Heavy burning observed on timber close to the ripping lip indicated slow burning at that point. Because of the gradient of the road, any accumulation of firedamp would have been thickest at the face of the ripping. This view was consistent with the degree of scorching of timber seen at floor level there.
Had the explosion originated anywhere but O.10's intake roadhead, the flame would have been forced onto O.10's face; this had not occurred.
Taking into account the probable concentration of the firedamp and that the flame reached the floor, an estimate of pure methane present at the time of the explosion was between 150 and 200 cubic feet.
This quantity would be enough to produce the violence necessary to raise coal dust farther outbye in O.10's intake.
Mr. F.J. Hartwell considered that the explosion was mainly of coal dust, principally that raised from conveyors as it died out on the tram haulage section of the main intake and on the main return.
Prolonged burning at O.18's return roadhead could only have been due to the inflammation of firedamp from open breaks, together with some firedamp from the adjacent waste.
Signs of extra violence found near O.10's supply roadhead might have been due to firedamp forced out of the waste by the explosion in the intake.
Mr. Hartwell carefully considered and put forward a possible alternative theory, visualising that a preliminary ignition might have occurred at O.10's supply roadhead that the flame then passed through the waste to ignite gas in O.10's intake roadhead, and this in turn caused the coal dust explosion.
In a number of cases flame has been proved to travel long distances in open breaks across wastes. To satisfy the theory in this case it was necessary to postulate either that the ignition in the supply roadhead coincided with the accumulation of firedamp at the intake roadhead, or that that the ignition in the supply roadhead forced firedamp, not on to the face, but by some other means into the intake roadhead, where it was virtually unmixed with air when reached by the flame.
Neither of these hypotheses seemed likely. Therefore he adhered to the opinion that the explosion started in O.10's intake roadhead.
All except one of the mining experts of the National Coal Board, the National Union of Mineworkers and H.M. Inspectorate agreed with this view.
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Source of firedamp.
Firedamp had not been found in O.10's intake ripping since 9th. May, suggesting that something unusual must have happened to cause an accumulation of about 150 cubic feet of firedamp in a period not longer than five hours or so between the night shift deputy's examination at about 5:30am, and the explosion.
Firedamp persisted after the explosion, two days later H.L.S. Johnston, Under manager of the No. 4 pit, observed one and a half percent midway up both O.10's intake and O.10's supply gate.
The ventilation not been restored, so a large emission of firedamp is not necessary to account for his observation.
The possibility arose of firedamp having migrated to the roadhead by layering along the roof of the roadway from the large cavity some 100 yards outbye on this road. Ventilation tests afterwards showed this was unlikely to have happened.
Tests in boreholes later drilled into the roof between the cavity and ripping did not indicate a substantial flow along breaks or bed separation channels.
Another possibility was that firedamp reached the roadhead as a consequence of displacement of firedamp by a large fall of roof in the waste.
Probably, any firedamp in the waste would normally be confined to the upper and return end of it, and if there had been such a fall, firedamp would have been forced out to the roadhead.
More likely than the displacement of already released firedamp, is the opening of new channels for firedamp emission, perhaps from the 'rider' coal, by ground movement.
There are many recorded cases of large feeders of firedamp having issued quickly. Such feeders have usually been associated with obviously abnormal ground movement and have not been short-lived.
Investigations after the explosion discovered neither such ground movements, nor a substantial feeder.
There could have been enough extra roof movement to create new channels for a slow issue of firedamp close to the roadhead itself.
J. Grindle, a repairer, spoke of the appearance of bed separation at the roadhead the day before the explosion and R.H. Law observed it after the shotfiring on the night shift.
A possible reason for a change in roadhead conditions was put forward by L.G. Fear, who drew attention to the existence of a small fault in the Marine workings the line of which, if continued, would have passed through the roadhead, and to a of change strata inclination near the roadhead.
Another possibility is that the pillar of coal between old O.10's face and the Marine workings, having been reduced to about 55 yards in width, must have been heavily loaded and so in a condition conducive to extra roof movement at its edges.
It is probable that the firedamp accumulated slowly from a small feeder close to the roadhead. With airflow of 5,000 cubic feet per minute in the twelve feet arched roadway, the velocity near the roof would have been very low and it is unlikely that, in the absence of a sheet, the air would have swept away any such accumulation.
There is no reason to suppose it had reached proportions detectable on a flame lamp, when the pre-shift inspection was made at 5:30a.m.
V. Harding, the deputy for O.10's unit, who was killed, may have examined the place at the beginning of his shift, if he had found an appreciable quantity of firedamp in the ripping, he would at least have erected a brattice sheet.
Even so, and allowing for slight dispersion, an issue into the ripping of little more than one cubic feet of firedamp per minute from 7:30a.m. onwards would have been sufficient to produce the minimum of 150 cubic feet that Hartwell estimated to have been involved in the beginning of the explosion.
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Means of ignition.
The investigation ruled out as possible causes of ignition, safety lamps, and electrical or mechanical plant used.
Contraband.
Contraband was ruled out as a means of ignition.
Two live matches, an unsmoked cigarette and a plastic bag were found.
Striking a match did not cause the explosion; the point of ignition was at O.10's intake roadhead, the nearest body was 100 yards away.
Shotfiring.
The possibility of ignition by shotfiring was considered.
L.R. James Head of the Safety Department, National Union of Mineworkers, South Wales Area, believed this was the cause of the explosion.
A round of four shots fired in the roof ripping near O.10's intake roadhead, at about 3:00a.m., on the previous night shift, could conceivably have ignited a continuous feed of gas in a bed separation or other break.
A 'hanging flame' sometimes, rarely, continues to burn, and could cause an explosion should a mixture of air and firedamp move upon it.
The omission of stemming from the back of shotholes in O'10's intake face rippings would have increased the risk of ignition in a roof break a little beyond the hole, and therefore undetectable.
It is probable that bed separation evident after the explosion was present to some effect before the shots were fired and there would have been some firedamp in the overlying beds.
Since 1934, (26 year period) British records of 'hanging flame' incidents numbered 24.
Six arose from shots fired in coal, seventeen in ripping shots.
Three could not be closely located from the information given, but it seemed that thirteen others occurred after firing shots in return roadheads.
The only ignition that led to a disaster was also the only one that occurred in an intake road.
This was at North Gawber Colliery in 1935. In this case the intake road was at the rise end of a face and near a partly closed airway leading to a face in advance of it.
In none of the cases did ignition occur in conditions similar to those in O.10's intake roadhead.
Difficulty was experienced in visualising circumstances in which firedamp in sufficient quantity to account for the explosion could, over a period of seven hours or so, have accumulated in the ripping without reaching a flame left from shotfiring, unless the flame was in a bed separation break in the lower part of the ripping.
That was thought possible, but not at all probable.
Frictional ignition.
Many witnesses described sparks which were produced either, when wedges were knocked out of the clamps of friction props or roof bar joints, or when released props, in falling struck supports still in position.
It was well known that sparks could be produced in this way or from operations like striking the edge of a prop with a hammer.
Investigation failed to show that sparks liable to cause ignition of firedamp are produced by this kind of steel-to-steel contact.
There was no history of such an ignition.
Sparks, (frictional heatings), resulting from impact involving certain kinds of rock are dangerous.
Firedamp can be ignited when machine cutting picks strike quartzitic rock or pyrites.
This did not happen in this explosion, as the machines had not been cutting for some time before the explosion.
Firedamp may be ignited from a particular type of blow from a steel hand pick on some kinds of rock. M.J. Burgess and R.B. Wheeler, were able to obtain ignitions in the laboratory, they recorded seven such cases in 1930 in a Safety in Mines Research Paper.
The Safety in Mines Research Establishment designed apparatus to simulate mechanically the type of blow that causes ignition with a hand pick.
Tests were made in an explosive atmosphere with samples of quartzitic sandstone that had been exposed in O.10's intake roadhead.
Four ignitions were obtained in six tests, during which the rocks were struck 130 blows.
A specimen of rock obtained from the roof of O'10's supply roadhead containing an intrusion comparable to the rock in O'10's intake roadhead was also tested and an ignition was obtained after about 200 impacts.
At the time of the explosion, the only place where quartzitic rock might have been struck with a hand pick was at O.10's supply roadhead. Hartwell, in evidence, discussed the possibility that firedamp was ignited there, but for reasons already given, this seems highly unlikely.
The Safety in Mines Research Establishment examined the possibility of rock on rock friction causing a firedamp explosion.
The results of tests by Burgess and Wheeler were reported on in 1928.
Other tests of this kind were made and reported on in The Safety in Mines Research Establishment Annual Report 1959.
The apparatus used consists of a rock 'slider' which is pressed with known force against the periphery of a rotating rock wheel in an explosive atmosphere.
The pressure between the surfaces is measured, and the time between the application of the load and any ignition of firedamp is taken.
Ignition has been obtained with quartzitic rock. The greater the speed of the wheel and the longer the duration of the friction, the more likely it is that ignition will occur.
Deductions from these experiments were that, to produce an incendive condition, a suitable rock would first have to fall a distance sufficient to gain the necessary speed and then slide some distance on another rock; the shorter the fall of rock, the longer would have to be the slide.
Mr. Rogers (Chief H.M.I. and author of this report) examined the available records of ignitions believed to be due to either impact of rock on rock or of rock on steel. The later must include the possibility that the incendive impact may have been between rocks.
The subject was so important that Mr. Rodgers considered the following collieries where ignitions by impact between rocks and between rocks and steel occurred: -
Maindy Colliery, 1896:
In the clearing of a fall, a cavity 18 feet high was created; a fall in the cavity is believed to have been responsible for an explosion occurring whilst no one was in the mine.
Ferndale Colliery, 1907:
A small quantity of gas was believed to have been ignited by a fall of strong siliceous rock from a place about 12 feet above floor level during the clearing of debris brought down in repair work.
Belle Vue Colliery, Alberta, Canada, 1910-11:
Three separate explosions occurred during the extraction of pillars in a 13 feet thick seam inclined at an angle of 45 degrees; it is believed the ignitions were due to collisions between pieces of bituminous sandstone as they fell down the steeply inclined roads.
Lletty Shenkin Colliery, Cwmbach, 1913:
Repairers were working at a fall when another large fall of stone occurred; they saw flame rising when the stone fell on some iron bars.
Minnie Pit, Podmore Hall, Staffordshire. (155 killed). 1918:
The fall of siliceous stone from a place about 12 feet above the floor of a thick coal seam worked by pillar and stall was given as a possible cause of the explosion.
Mine in Germany, 1922:
An explosion was produced by the impact of a large piece of sandstone on a steel roof support arch.
Hillcrest Mine, Alberta, Canada, 1926:
Frictional sparks or heating due to falling and sliding rock were possible causes of the ignition of firedamp.
Marine Colliery, Monmouthshire, 1927: (52 killed).
Explosion may have been due to stone falling on other stone, which had already fallen. The probable place of ignition was on a working face, where a fall involving a bed of siliceous sandstone was being cleared.
Cwm Colliery, 1949:
A fall occurred in a cavity at a roadhead; stone collapsed about 8 feet on to an arch girder and produced an ignition.
Lewis Merthyr Colliery, 1957:
Hard 'clift' fell from a roadhead cavity for a distance of 20 feet on to arch girders and produced an ignition.
Mine in Virginia, 1958:
Supports had been withdrawn from a section; an explosion associated with a fall occurred. Miners 50 to 75 feet from the fall saw sparks and a flash of fire just before the explosion.
It appeared that, if quartzitic rock falls and strikes either a steel object or possibly pieces of similar rock with sufficient impact, an incendive condition may result.
Hartwell suggested that the impact of the mechanised pick used in the experiments he described would have been about the equivalent to that of rock weighing 260 lbs. falling three and a half feet onto a steel object.
He thought the most probable cause of the explosion was a fall of rock bring down with it firedamp that had accumulated at the ripping and that one of the larger pieces of rock struck the canopy and produced an incendive condition and caused inflammation of the surrounding atmosphere.
Pieces of quartzitic rock, the largest estimated to weighing about 240 lbs. were found on the ground and on the canopy under O.10's intake ripping. Some could have fallen a distance of six feet.
The mechanics of firedamp being brought down from near the roof by falling stone and then mixing with air have been demonstrated with Perspex models of the roadheads in which the explosions occurred at Lewis Merthyr Colliery and at Sutton Colliery in 1957. The models were made at the Buxton Station of the Safety in Mines Research Establishment.
The evidence was not completely satisfying, but Mr. Rodgers inclined to the view that firedamp was brought down by a fall of roof and was ignited by frictional heat at the point of impact between quartzitic stone and the steel girder forming the top of one side of the canopy.
Questions being asked.
If a fall of stone of a not uncommon nature for a distance of six feet or so may be dangerous, what is the degree of risk involved in the routine collapse of roof in wastes?
There are no records of this type of ignition of firedamp in longwall wastes in this country. For ignition to occur a number of conditions must be present; a fall of a certain kind of rock, the right type and strength of impact, and the presence at or about the point of impact of a firedamp-air mixture within a relatively narrow range.
Whether the conditions of the tests, with frequent pick blows in the same place, resemble what can occur in practice.
To what extent such impacts can be related to the impact of falling stone.
Whether the revolving wheel test provides reliable data upon which to found conclusions regarding falling stone.
To what extent the ignition hazard is affected by the mass of falling stone and its velocity.
Whether there is some peculiarity in the mines in South Wales, such as nature of stone, which may account for the preponderance there of these ignitions.
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Minority view.
A. Davies, a National Union of Mineworkers' Inspector, advanced the theory that the explosion started as a result of firing of a ripping shot in O.18's return roadhead.
Well kept records of explosive issued and returned showed that a detonator and a pound of explosive, issued to the deputy of O.18's unit on the morning of the explosion, were not recovered afterwards.
Davies thought that a shot may have been fired in the right hand side of the ripping just before the explosion, that this may have ignited firedamp which had continued to burn and that the deputy and others were at the time of the explosion fetching stone dust in order to put out the flame.
Rogers saw nothing in this place to make him think that a shot containing one pound of explosive might have been fired in the ripping. He thought it more probable that the missing explosive had been used in coal near the rib-side as there were large lumps which had apparently been 'turned back' a sufficient distance from the face to make a track for the coal cutting machine.
Rogers thought the conclusive evidence against the theory was; if an ignition had taken place in O.18's roadhead, the direction of flame would have been completely contrary to the indications found.
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General discussion.
Contraband and searching.
The statutory requirements relating to the systematic search of underground workers for smoking materials had not been carried out at the No. 5 Pit since February 1959, when workmen who had been carrying out the search ceased doing it because of a payment matter.
The manager said he arranged for under-officials to search instead.
A fortnight before the explosion, it came to his notice that his arrangements had broken down. He again confirmed his earlier instructions to the under-officials but no evidence of any follow-up action to see that it was observed.
After the explosion it was discovered that they had not been.
The manager is responsible for ensuring the observance of searching, and if these arrangements are not carried out; for ensuring no person goes below ground. Rogers thought, others may not feel satisfied that they did all they might have done in the matter.
He was disturbed by the evidence that smoking materials had been taken below ground at Six Bells Colliery and was shocked to find no dissent from the implication that the plastic bag found in the water bottle was a provision intended by someone at some time to defeat a searcher with the object of smoking below ground.
Roof Support.
The general standard of roof control on O.10's face was good. The seam roof at the intake roadhead was not insecure but the system of support at this place, and the implementation of it, left something to be desired. Chocks could have been incorporated in to the system of support.
The hydraulic props used were suitable for roadheads but the density there was less than on the remainder of the face. Additional props should have been set at the margins of ground to be brought down by shotfiring.
Long experience has shown a need for more than average density of supports at roadheads, especially where there is a machine stable, which increase the distance from pack to face. Packs were not completed as close to the face as they should have been, a matter of prime importance at roadheads.
Similar criticisms applied to the supports of O.18's return roadhead.
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Firedamp determinations.
The firedamp content in the general body of air at the statutory measuring point, had on occasions exceeded one percent, the manager had failed to notify the H,I. Inspectorate.
A number of irregularities also existed regarding the making and recording of determinations. Some results had not been entered in the book provided for this purpose, and some of those recorded referred to times other than the later part of a cutting shift.
There was no record for O.12 unit.
Firedamp detection.
A number of persons carrying flame safety lamps had not been trained and certified in their use.
It was suggested at the Inquiry that deputies should be provided with methanometers and probes for examining inaccessible places.
Mr. Rogers felt there was a case for wider use of these aids by ventilation officers in special investigation work, but not for the time being by deputies for routine inspections.
He agreed with suggestions that deputies should be provided as soon as possible with a better means of examining for firedamp in high places, not only because it is difficult for them to reach the roof, but because it is known that present types of lamps may not give accurate indications of thin roof layers. Flame safety lamps so equipped that a sample may be brought down from the roof to the lamp by an aspirator and a tube are becoming available.
Emission of firedamp.
O.18's.
O.18's was advancing into an area not likely to have been drained of firedamp to any appreciable extent by previous workings. The nearest seam extracted was the upper leaf of the Black Vein, some 60 yards above.
A fairly substantial emission of firedamp was expected and did occur. The last measurement before the explosion, revealed 9,450 cubic feet of air per minute in the return airway, and contained one percent of firedamp at a point 30 feet from the face.
The 'make' of firedamp therefore was about 94 cubic feet a minute.
Firedamp appearances were quite frequent, mainly in the intake rippings, the highest point in the unit, until substituting twelve feet arches with eight feet arches reduced the thickness of roof.
O.10's
The 'make' of firedamp in O.10's unit was less than 17 cubic feet per minute when last calculated before the explosion. The percentage of firedamp at the return end of the face was only one-quarter of one percent.
Firedamp was frequently reported by the deputies mainly at or near the return end of the face.
It was suggested at the Inquiry that a system of firedamp drainage by boreholes over the gob might have averted the explosion.
Rogers did not subscribe to that view, but he considered that if that system had been adopted in O.18's unit it would have saved a lot of trouble and anxiety. The N.U.M. lodge chairman was concerned, because he discussed it with the manager on at least one occasion before the explosion.
Long before this the manager and the group manager had demonstrated their concern by taking part in special methanometer surveys.
The management considered firedamp drainage; Rogers thought that this unit (O.18's) was one where firedamp drainage might have been adopted. It could conceivably have been more effective that the local air deflection measures taken, by assisting the natural buoyant firedamp to rise to the drainage holes and so away from the edges of the working.
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Air velocities.
O.10's unit made less than one-fifth of the amount of firedamp given off in O.18's unit, but the air quantity was also less by about one-half. The velocity on O.10's face was of the order of 100 feet per minute, substantially below the figure of 150 feet per minute recommended originally as a dust preventative measure in the Third Report of the Research Committee of the Monmouthshire and South Wales Coal Owners' Association, and subsequently quoted by the National Coal Board as desirable for faces in new and reconstructed collieries.
Air velocity on the face is generally related to the velocity in the roadways serving the face; in thin seams a face velocity of 150 feet per minute might mean a low velocity in the roadway, which would be conducive to roof-layering of firedamp.
When air has a fairly high velocity, it does to some extent sweep places just out of the general airflow and it can be directed with some force to such places as ripping edges.
Many explosions have occurred in seams that are not very gassy and have been attributed to the unexpected emission of firedamp, often in no great quantity and probably at a moderate rate.
Emission of firedamp can rarely be predicted accurately, enough air should be produced to deal with occasional abnormal emissions.
If there had there been on O.10's, unit the same quantity of air that O.18's unit had, and a means provided of deflecting a substantial part of this air to the ripping, Rogers doubted if firedamp would have accumulated in a quantity sufficient to start a coal dust explosion.
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Air ejectors.
Air moving machines known as 'Venturis'.
A suggestion at the Inquiry was that the two in O.18's unit were 'objectionable'.
Neither contributed to the explosion but attention was drawn to the hazard inherent in inefficient earthing. One of them was open to criticism.
Air separation doors.
Prolonged opening of any separation door may adversely affect face ventilation.
Evidence was heard which suggested this happed from time to time in W District.
Materials for O.10 unit had to pass through three sets of doors and be man-handled part of the way. A process Mr. Rogers thought was not satisfactory from the aspect of ventilation or transport.
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Aluminium alloys.
Mr. Rogers excluded this as a possible source of ignition. The aluminium components of the stage loader motor were situated 30 yards from the face of O.10's intake.
Incendive sparks can readily be produced by friction between alloy and rusty steel. Following the explosion at Glyncorrwg Colliery in 1954, restrictions on the use of equipment partly or wholly of aluminium alloy were imposed by the National Coal Board, after discussion with the Ministry of Power. These restrictions applied only at the coal face.
Mr. Rogers thought the subject should be re-examined with a view to extending the area of restriction to all parts of the mine where firedamp may be a hazard.
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Shotfiring practice.
Conflicting evidence was given on shotfiring practice. Many workmen said they had never seen a break detector used. Only one was found after the explosion and there was no evidence to suggest the existence of any other in W District.
It was contended by those concerned that one shotfirer normally fired all the shots on his shift, but as happened occasionally, a deputy also fired shots, the deputy and the shotfirer arranged not to fire at the same time so they could share the detector.
The break detector produced had been well used at some time. The point of the prong was worn to such an extent that it did not satisfy the requirements of the official approval. With a prong in this condition a shotfirer could well fail to detect a completely longitudinal break wide enough to be dangerous.
Another irregularity alleged by many witnesses was that specially provided stemming bags of fireproof paper were sometimes partly, or wholly filled with coal instead of with suitable inert material.
Twenty-two bags filled with fine coal were found on O.10's unit after the explosion.
Mr. Rogers advised managements generally to forthwith check the position at their collieries, and that the proper provision of suitable stemming material at any place where a shot is fired is a very important safety matter.
The round of four shots fired in O.10's ripping on the night-shift before the explosion were fired when the only person in the unit, other than the deputy, were the shotfirer and his assistant. They did not advance the horse-head supports to the ground exposed by the shotfiring.
It was apparently not unusual to fire shots towards the end of one shift and leave the setting of supports to the newly exposed ground for a following shift.
The argument for firing shots between shifts was that fewer persons were at risk.
However, Mr. Rogers thought it was essential that operations associated with shotfiring - the preparatory setting of additional supports around the margins, the withdrawal of the supports from beneath the roof to be brought down and the supporting of the newly exposed ground - should be carried out in sequence with the minimum of delay. This is important generally as a contribution to good roof control and as a safeguard against falling stones.
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Coal Dust Dangers.
The National Coal Board's Department instruction in force at the time of the explosion at Six Bells Colliery seems to have required 'primary' stone dust barriers in the W District at: -
1. O.18's loader gate, not more than 100 yards inbye of the transfer point onto the conveyor in the main intake.
2. O.10's loader gate, not more than 100 yards inbye of the transfer point onto the conveyor in the main intake.
3. And possibly The main intake at a point, not more than 100 yards inbye or outbye of the transfer point of O.12's gate belt.
The extent of the explosion might possibly have been much less had barriers been provided at these places.
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Mr. Rogers Conclusions.
No one can say with certainty where or by what means the explosion at Six Bells Colliery started.
But I think that: -
1. The explosion started as an ignition of firedamp in the intake roadhead roof ripping of O.10 intake.
2. The accumulation of firedamp might have been prevented had there been a hurdle sheet near the face ripping.
3. The cause of ignition was frictional heat produced by the impact of a piece of quartzitic rock falling for a distance of about six feet, from the roof exposed by shotfiring, onto a steel girder forming part of a conveyor canopy.
4. The fall of this rock might have been prevented had the roof between the last-set steel arch and the new ripping face been supported immediately after the firing of a round of shots there about seven hours before.
5. An explosion of firedamp alone might not have caused any casualties, as there was nobody in the vicinity at the time.
6. The explosion which spread throughout most of the district was one mainly of coal dust raised on the conveyor roads.
7. The coal dust might possibly have been confined to O.10 unit had there been sufficient stone dust barriers suitably placed.
O.10's Loader gate.
O.18's return roadhead.
Six Bells plan1.
Six Bells Colliery.
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