THE INSPECTION
HAPTON VALLEY
Burnley, Lancashire. 22nd March 1962

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.