The Inspection

Immediately the recovery operations had been completed H. M. Inspector of Mines, accompanied by representatives of the management and the workmen carried out a preliminary inspection of the greater part of the mine including the explosion area.

Shortly afterwards the Inspector and scientists from the Safety in Mines Research Establishment made other inspections of the explosion area. Neither inspection revealed any obvious point of ignition, ignition agent of the presence of firedamp. The Inspector and the scientists commenced and extremely detailed investigation which lasted two months.

A detailed picture of the explosion area emerged from these investigations. Specimens of fibrous material collected in the intake gate were examined microscopically and did not show signs of having been subjected to heat. Although there was a thin layer of explosion dust on the conveyor gate, the dry stone dust on the barriers had not been disturbed.

Specimens collected at points along the face indicated that the flame had travelled down the face to within about thirty yards of that stable. Much of that part of the face affected by flame and there were unmistakable signs of coking on the intake sides of the props, an indication that flame had come from the return side. Detonator leads coming from charged shotholes in the return gate stable showed obvious signs of charring on the first twenty yards of the face from the intake but further along the face where signs of some violence, although roof supports had not been affected.

Microscopic examination of fibrous specimens collected from an area between the face ripping and a point 550 yards outbye, showed signs of exposure to flame. Beyond this point to the junction of the No.5 District return, specimens had been subject to some heat but had not been carbonised. There were signs of blast near the ripping but the evidence as to the direction in this area was not positive. In the length of gate between points 28 yards and 180 yards outbye of the ripping, there were unmistakable signs of blast in the direction of the face. Outbye of this area although there were a small number of small roof cavities and the floor was strewn with fallen stone, backing boards and other debris there were no indications of blast up to a point 280 yards from the ripping.

There was an electric section switch had been moved outbye presumably by blast. In the next 40 yards of roadway the damage from blast was the most sever in the whole of the affected area. In this length a number of badly damaged tubs and bogies were found derailed and smashed near the return wheel of the endless rope haulage. The wheel the carrying frame and the arch girder supporting it had all been displaced in an outbye direction but there was no sign of abrasion on the return wheel or its framework.

For a further 200 yards outbye signs of damage were much less in evidence but there had evidently been strong blast some 650 yards from the ripping where a tank had been displaced. From there to the junction with No.5 District return there were signs of only slight blast. Nowhere in the area was there any indication of a slow burning of rich firedamp/air mixture. The results of the examination suggest that the blast had affected in varying degree nearly 1000 yards of face and roadway of which 680 yards had been exposed to flame.

Ventilation measurements made shortly after the explosion indicated that the quantity of air leaving the district varied from 14,200 to 15,000 cubic feet per minute.

The firedamp content of this air as ,measured by a methaneometer was between .6 and .8 per cent. The colliery records show that before the explosion in the quantity of air passing was higher and the percentage of firedamp lower but the actual make of firedamp was about the same. Excluding that being drawn off by the drainage system, this was about 100 cubic feet per minute. Discarded firedamp drainage holes were sometimes sealed by the insertion of wooden plugs but some had been left unsealed. Six of the unsealed holes in a length of from 321 to 709 yards from the face ripping were examined for firedamp issuing from them. By using a methaneometer and probe firedamp was found in five holes but only one at 472 yards from the ripping gave any indication of continuing flow. This was small in quantity but up to 30 per cent was detected at the mouth of the hole. Relatively high concentrations of firedamp were found in a number of small cavities in the roof of the return gate but it was estimated that the total volume of pure firedamp in these cavities could not have been more than 50 cubic feet.

On the 24th March one of HM. Inspectors made a ventilation survey in the return gate stable without a brattice sheet in position. By using artificially produced vapour clouds as a tracer he found that only a small proportion of the air leaving the face entered the stable. Here there was very marked recirculation. Using a methaneometer with a probe attachment the inspector found high concentrations of firedamp at a number of points between the roof and the top of the fallen coal but the total quantity involved was very small. On the same occasion the inspector using the same equipment made determinations of the firedamp content in the waste some of them from points 7 to 8 feet above the seam roof level. In no case was the concentration higher than that in the general body of the air at the face.

Although the quantity of air leaving the district immediately after the explosion was found to be substantially less than that record from the last statuary measurements made before the explosion later measurements showed that the quantity had increased to between 16.000 to 17,000 cubic feet per minute with a firedamp content of .4 per cent. Because of the frequency with which the men and materials were known to pass through doors at the Cut-back and men through the doors at James Bradleys Junction it was decided to measure the effect of opening these doors on the ventilation district.

Two tests were carried out one with the doors at James Bradleys Junction fully open and the other with the doors at the Cut-back partially open. In the first test the normal quantity of air reaching the face was reduced to 6,000 cubic feet per minute and in the second by 5,000 cubic feet per minute.

In the course of the investigation two hessian sacks were found each containing the same type of Eq.S explosive in the cartridge form. One near the intake gate ripping contained 12 pounds on the other near the return gate ripping 56 pounds. Although the first 14 yards of the face from the intake gate stable 10 shotholes had been drilled in the bottom of the coal, Nine of these had been charged and stemmed and a single shot exploder with connected cable was lying between the ninth and tenth holes.

In the return gate stable seven shotholes had been drilled and six of them charged and stemmed. The charged shotholes were disposed in two groups, two near the ribside and four to the left side of the stable. In the short length between the two groups there was a heap of broken coal lying against the face. It was clear from the evidence in the roof and face that at least two shots had been fired in the vicinity. Of the group of four shotholes the one immediately next to the broken coal and about 12 feet from the face buttock invited particular attention. It was observed that the coal on the loose side of this hole was fractured by innumerable fine cracks. When this coal was removed by hand a plug or stemming at the front of the hole and three cartridges of Eq.S explosive were revealed. The latter were impacted together as through they had been subjected to pressure from the back of the hole, and the inner end of the last cartridge was covered by a coating of coal dust 1/8 " thick. The shothole was subsequently found to extend 12 inches beyond the last cartridge but this section was empty. A primer cartridge was not found and there was no evidence to suggest that the shot had blown out laterally. Two detonator wires were found in the hole one reached only as far as the stemming but the other extended to the inner end of the recovered part of the charge. Nothing unusual was observed in the condition of the remaining five charged holes and they were subsequently fired without incident under the supervision of H.M. Inspectors.

A shotfiring cable without detonator leads attached extended from the face side of the conveyer over a roof bar under the return gate ripping on to the ripping debris where the remainder was tied in a hank with one of the leads connected to a single shot exploder. A shotfiring exploder key was later found in the clothing of Halstead, the shotfirer whose body was recovered from nearby. A case subsequently found to contain 31 detonators was also found in Halsted's clothing. Some of these with others were taken from the colliery magazine 25 in all were sent to the Armament Research and Development Establishment, Woolwich for X-ray examination and test. They were found to be in normal in all respects.

Explosive from the pit and from the colliery magazine when tested for behaviour and composition proved to be normal. Tests for sensitivity to initiation of detonation on some of the explosive referred to in paragraph 51 showed that it had not deteriorated.

The five safety lamps and 53 electric cap lamps (some incomplete) recovered from the district were sent for test. The flame lamps and 28 of the cap lamps were found to be in approved condition securely locked and in working order. The remainder of the electric cap lamps had sustained some damage but this was considered to have been caused by the explosion.

Smoking materials were not found either during the underground investigation or when the effects of the victims were examined on the surface. No combustible material was found. No electrical defect was found. All signalling and exploders were found to be in good condition. The apparatus was examined to look for frictional heat and all was found functional. The seams included pyrites nodules known locally as 'bobbers' and ignitions of firedamp had been known at the colliery attributed to cutter picks striking them. Because of smears left by aluminium alloys left with rusty steel a thermite reaction could arise. A fire hose nozzle was tested and found that it could leave aluminium smears but there was no indication that it had done so. In the length of the return gate ripping there were 18 metal foils from the wrappings used for confectionery and chewing tobacco. When pieces of the specimens were submitted to glancing blows with rusty steel in a firedamp atmosphere ignition was obtained in all but two specimens. These foil wrappings which are generally of aluminium usually have paper backing sometimes waxed where this backing was retained ignition could not be obtained.

The two specimens which had signs of fusion when picked up 300 yards from the return gate ripping. The signs of fusion were very similar to the signs on the pieces of aluminium foil which had given incendive flashes when tested. The state of the roof was the same before and after the explosion. The roof breaks observed at the face by the afternoon and night deputies were not accompanied by marked displacement and were not unusual. The deputies described the wastes as behaving normally. The small cavities in the gates were attributed to the force of the explosion.