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

Mr. F.J. Hartwell, the Senior Principle Scientific Officer in charge of the S.M.R.E. examination summarised the point of ignition and the spread of the explosion. These were based on three facts.

• First, none of the fibrous material had been exposed to flame for more than a very short time.
• Second, at no point in the explosion area was there evidence of slow burning by rich firedamp
• Third there had been a rapid moving of flame accompanied by considerable violence although not so great as would have been expected from the most explosive mixture of firedamp and air with a relatively ‘quiet zone’ between 180 yards and 280 yards outbye of the return gate ripping.

These three facts led to the belief that the explosion originated in the ‘quiet zone’.

The signs were, that the flame had travelled outbye from this area with some violence to a point about 550 yards from the face ripping and possibly less violence inbye to the return gate stable. Here it was probable that there had been added firedamp which would have added to the violence sufficiently to raise some coal dust along the face contributing to the spread of the flame and blast in that direction.

Mr. Hartwell added that there might have been firedamp in the return gate stable and that flame from such an ignition could have blown out onto the face causing a minor coal dust explosion there. If this did occur, flame from the stable could have been propagated down the return gate in a ‘trail’ of firedamp along the roof to a body of firedamp which would have exploded with flame and blast in both directions.

Either possibility would have required a presence in the return gate of a reasonably well mixed volume of firedamp and air. The violence of the explosion was of 8 per cent mixture of gas and air. He estimated that about 2,000 cubic feet of firedamp would have had to be present to have remained undispersed it would have appeared rather quickly.

There was no scientific evidence to show where the firedamp came from but he thought that the most probable place was along the face or the return gate stable. Dr. Willett for the N.C.B. thought that it came from ‘either the sold coal in the vicinity of the stable or the waste’. Mr. Clough, H.M. Divisional Inspector of Mines was firmly of the opinion that it came from waste because neither the face nor in the return gate stable where the strata breaks or displaced coal were there more common signs of a rapid emission.

All were of the opinion that only frictional heat and explosives need be considered as the means of ignition. Mr. Crawford of N.A.C.O.D.S. suggested that the firedamp had been ignited by a frictional spark or thermite reaction as a result of vehicles running uncontrolled down the return gate. No other form of frictional heat was considered as a possible source of ignition.

Mr. J. Gormley for N.U.M. and Mr. Clough were both of the opinion that the shot fired in the return stable was responsible for ignition. Shotfiring operations were in progress when the explosion occurred. Some of the men that died were grouped some little way down the return gate as if sheltering from shotfiring and Madden and Fisk thought that the explosion followed a shot. However if the explosion occurred after a shot the shotfirer must have had time to return the firing key to his pocket and this was found not to be the case.

Mr. Clough thought the ignition was in the stable would have been from the gas from broken coal and that this flame in turn ignited gas passing from the face into the return gate after being emitted from the waste. In these circumstances it was concluded that Halstead would have had time to return the firing key into his pocket and to begin returning to the shotholes before he realised that gas was burning in the stable.

In conclusion the commissioner was not able to give an entirely satisfactory explanation either of the source of the firedamp or of the means of ignition.

It was accepted that the explosion was caused by firedamp present in the return gate. The possibility that this was caused by an interruption of the ventilating current would mean that the ventilation would have to be stopped for two minutes and there is no evidence that this occurred.

In considering the possibility of a rapid emission of firedamp into the return gate stable it was possible that the required explosive mixture could have been formed in the return gate. On ignition the blast ahead of the flame travelling up the return gate could have dispersed and rich firedamp in the stable as to cause it to flame and continue the explosion with the help of coal dust along the face.

Firedamp from the high level in the waste could have been pushed out onto the face but it was felt this would have required a heavy strata movement which would be audible but there was no evidence of this. An emission from the waste could however have taken place quietly had the firedamp been hanging close to the edge of the waste but after the explosion efforts to establish the location of the firedamp were unsuccessful even though probes were pushed up into the waste to a distance of 7 to 8 feet above the seam roof level.