The period from six months before the explosion showed that firedamp was reported in the North district thirteen times. On most of these occasions, the auxiliary fan was out of order or the tubing was partially closed by a fall of roof. When remedied, the gas quickly cleared. Only five of these reports were of gas in the North-West area and on one of these occasions the men were withdrawn. This was on 1st February 1945, when the deputy, Dobson, found gas at 8 to 8.30 a.m. and three percent firedamp was present in the ‘North-West top heading, due to a breakdown of the electric fan’. The statutory reports state that at 12.30 to 1 p.m. on the same day a further examination was made and Dobson reported, ‘New fan installed, place clear and fence removed’. The manager who was in the district on that day stated that this had occurred when the top level had advanced beyond the 11th slit and just short of the 12th, the lower level had reached the 11th slit which was being driven downhill but it had not connected with the lower level.
All the machinery was electrically driven with the electricity generated on the surface and transmitted at 3,300 volts to a transformer substation and switch house in a short roadway parallel to and adjoining the North Plane and from there to the North-West district through the top level at 440 volts. The sub-station had two Reyrolle, Type F, oil circuit breakers, each fitted with earth leakage protection. One of the circuit breakers controlled all the apparatus in 6’s and 7’s headings and the other for 3’s and 4’s headings with the cable for this being taken along the lower level. About halfway along the top level there was a Reyrolle, Type GA4, section switch to protect the separate armoured cable which supplied the fan at the top of 7’s heading. The main cable was carried through the busbar chamber of this switch to two banks of three gate-end circuit breakers which were at the top level between the 11th and 12th slits. They were connected by four feet of pliable armoured cable. The first bank of Reyrolle, TypeGA1 switches supplied three conveyors. The second had Type GA1 switches with one controlling a flexible cable to the coal cutter in 6’s heading and the other, with a similar cable, went to the Joy loader in 7’s heading. A type GA2 switch unit controlled a flexible cable to the drilling machine.
The cable to the Joy loader had four cores and a bare centre earth conductor. The three insulated power cores were each surrounded by a copper screen, all in electrical contact with the bare earth conductor. The fourth core was used as the pilot and was unscreened. The Reyrolle GA1 switch was covered by the Buxton F.L.P. Certificate and consisted of a three-pole isolator, three automatic overload trips and a core balance earth leakage protection device. Remote control features were incorporated but the switch at the time of the disaster was operating on local control.
In 1936, a Safety Department was set up by the Company which had grown and at the time of the disaster consisted of a Senior Inspector with two full-time Junior Inspectors, one at Manvers Main Colliery and the other at Barnborough Colliery, in addition there were three assistants at the former colliery, two at the latter and five other members of staff. It was evident that the Company had shown an active interest in safety and had gone to considerable expense and trouble to ensure a high standard. No one was left alive in the explosion area so no light could be thrown on what had happened. The position on the previous shifts, Saturday 3rd March and in particular what happened on the afternoon shift of that day did provide some answers.
It had been arranged that during the weekend, modifications were to be made in the method of conveying the coal in the 6’s and 7’s headings and the day overman, Harold Mann, in consultation with the deputies, planned the work to be done. The chain conveyor in 7’s heading, running from the face to the main belt conveyor in the top level, was becoming too long, and it was proposed to shorten it to deliver on to the chain conveyor in the second cross slit. The direction of this running was to be reversed and to install a belt conveyor in 6’s heading from the first cross slit to the top level fed by the chain conveyor from the face of 6’s heading and that in the second cross slit. To do this the driving gear heads had to be moved along with other parts of the machinery into the headings and to move them inbye, required the erection of the belt conveyor in 6’s heading. In the bottom level no rails were laid, but there was a trolley or bogie with pneumatic tyres, one of which had been missing for some days and it was suggested that this might be used to transport material but there was no evidence that this had to be done. The only other solution was to move the pans which weighed two to three hundred weights by hand. After the explosion the trolley was found opposite the 7th slit damaged and lying on it’s side with one wheel off.
On the Saturday, the day shift deputy, Frank Dobson, went down at 5.40 a.m. and came up about 1 p.m. He made two inspections on the North-West side, the second between 11.30 a.m. and 12.30 p.m. and he found that all was in order and failed to detect any firedamp in the headings. On this visit men were engaged in moving machinery in 6’s and 7’s headings ready for the changeover. Coal cutting was done in 7’s heading twice during the shift and once in the 6’s heading. The coal cutter in 7’s heading was left about two yards from the face and that in 6’s heading on the low side of the second slit from the face. Both these machines were found in theses positions after the explosion.
The Saturday afternoon shift deputy, Laurence Wroe, went down the pit at 12.10 p.m. and came up at about 8 p.m. He had forty three men in the North district, eighteen of whom were working in the North-West. Six of these men were moving pans along the return road and by the end of the shift he had got a number of men just beyond the chain conveyor in the 6th slit and others were on the outbye side. Four men were moving the chain conveyor gear head down the 7’s heading from the top level by means of the Joy loader. Wroe’s first inspection in the North-West was made about 12.30 p.m. and he found all in good order. The second inspection was about 6 p.m. by which time all the men had left and in consequence of this he did not consider it necessary to inspect the face of the headings and he found no firedamp elsewhere. The auxiliary fan was not running at the time as it had been stopped by Crossley on his way put to the shaft when he switched off all current to the district.
Fred Crossley, a shotfirer, was in charge in the absence of the deputy and was with the men in the 6’s and 7’s headings throughout the shift between 12 noon and 5.30 p.m. when he went up the pit. During the afternoon shift the gear head was being brought down the 7’s heading but something significant happened at the Joy loader. John Wilson, a Joy loader operator who had about eighteen months experience was operating the machine when in his own words, ‘the cable got trapped in between the Joy loader and the gear head of the chain conveyor, on top of the Joy loader’. There was slack cable in front of the loader and the cable got fast on a pommel screw. This was followed by a flash and the cutting off of the current. Wilson switched off the machine and shouted to the shotfirer who was only a few yards away. After the loader had been pulled forward by Sylvesters a sufficient distance to free the cable and it was found, when it was examined, that the cable was punctured through one of the cores. Crossley saw that the rubber was punctured but he did not notice the exposed core.
The flash occurred about 4.30 p.m. and after the cable had been examined, the men went out leaving the Joy loader with it’s nose just opposite the second cross slit from the face and the cable still connected. It was found in this position after the disaster. The cable was not removed from the gate end switch and Wilson did not withdraw the pommel at the gate end switch because he did not think it was necessary. Wilson went out intending to neutralise the loader gate end switch but he found that this had already been done. He did not notice if the flag of the Joy rider switch had dropped which would indicate that the earth leakage had tripped but he took this for granted. It was assumed by Crossley and Wilson that the gate end switch and also the switch to the transformer had tripped. They knew that the supply could be restored only by an electrician authorised to do so and with the proper tools.
Shortly before this incident, Crossley proceeded up the heading to the top level where he found the fan had stopped which suggested to him that the current had tripped outbye. He looked at the gate end switch controlling the Joy loader and though the red flag had dropped, but he could not be sure. He put the isolating switch in to neutral and saw that all the other five switches were in neutral. He made his way outbye at once to the transformer station at 7th North and put the power back to the fan having arranged with Joe Conroy to start the fan with the push button when the power was restored. To do this Crossley used his battery key which he had been told would do the job even though there were no electricians in the district that afternoon. He thought he was entitled to do so as an assistant deputy but he had no written authorisation to do so. By his actions the electrical system was made live to the switch panels between the 11th and 12th slits.
After this, Crossley went to the 8B face where he found the deputy Wroe and reported to him that the cable had been ‘nipped’ and an electrician would be needed. At the inquiry, Wroe did not remember being informed that there had been a flash on the cable but on coming out, Wroe left word with the onsetter that an electrician was to be informed next morning. He did not put it in the ‘detail book’ but expected that the cable would receive attention before it was necessary to use the Joy loader. The ‘detail book’ was a foolscap book that was kept in a ‘box hole’ about 30 yards from the pit bottom and the deputies entered particulars of what had been done on their shifts and anything of importance of which he thought the oncoming deputy should be made aware.
Glossary of Terms