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Home Office and Minnie Pit Management 1920
Researched by John Lumsdon
Sir John Baird (Under Secretary Home Office) July 1920 writes that the suggestions made in the report of the Chief Inspector of Mines in the Minnie Pit explosion in 1918 are being considered. The Home Secretary considered the question of prosecuting the management. In view, however, of the decision of the Courts in the Senghenydd case, it appeared doubtful whether proceedings could be taking successfully for breach of Section (62) (3) of the Coal Mines Act, and, after consideration of all the circumstances, it was decided that a persecution was not necessary. Since the explosion the management had taken proper precautions by stone dusting the roads, and the Inspector reported that the requirements of the Act were being fully observed.
The question of the prevention of danger from coal dust, had, Sir John adds, had now been placed on an entirely different footing by the new regulations dealing with the treatment of coal dust, which had now been finally settled. There was every ground for hoping that these regulations, which were based on the recommendations of the Explosion in Mines Committee, would prove an effective safeguard against terrible disasters as occurred at Senghenydd and the Minnie Pit.
Greater Safety in Mines
During the Coroner’s inquiry into the Minnie pit disaster in1918, Mr. W. walker, then acting Chief Inspector of Mines, announced the making of new Regulations, designed to minimise the danger of coal dust explosions. These Regulations are now operative and the paper which was read by Mr. A.L. Lovatt at Monday’s meeting 24th January 1921 of the North Staffordshire Mining Institute detailed the stone dusting methods which have been adopted at the Birchinwood collieries, to give effect to the Regulations.
At Birchinwood, as at other collieries, stone dusting has been in use prior to the issue of these statutory requirements, but, of course, methods have now been modified to conform to the new regulations.
The discussion, which followed the paper, was the most animated and useful that has taken place at the Institute for years, and it brought out new points and queries, which cannot fail to be of advantage. For example Mr. T.W.D. Gregory, Lecturer on mining chemistry at the central school of science and technology, raised the important question of the employment of limestone, which, by the form of the present regulations, may possibly be barred from use.
The theory in regard to the use of limestone for the stone dusting of mines obviously needs further investigation by research.
The claim is that in the case of an explosion carbon dioxide gas would be evolved from the limestone, by the heat from the explosive flame, acting as a dilution of the oxygen of the air and a check to the progress of the flame. This possible effect is, however, disputed by some experts, as it was on Monday by Mr. Henshaw. As the regulations stand, Mr. Gregory pointed out; the carbon dioxide contained in the limestone must be calculated on analysis as combustible matter, where as he contends, a special test should be provided for by which carbon dioxide should be calculated as forming part of the incombustibles. This, however, was but one question raised. Mr. Henshaw pointed out that a good deal of doubt had been thrown on the effectiveness of 50% of incombustible matter being sufficient to prevent the propagation of an explosion when it had once started and accumulated velocity and pressure.
As a further safeguard, he has therefore, adopted a system of stone dust barrages or barriers, designed to come into operation in the event of an explosion, with the object of containing the explosive wave to a limited section of the pit.
Quite apart from minimising the coal dust danger, the present compulsory practice of stone dusting mines is likely to have a beneficial effect, which, had not been taken into calculation. As is now known, that commonest of occupational deceases miners’ nystagmus, is chiefly due to the inadequacy of the illumination of mines.
The use of stone dust, by reason of its greater surface brightness as compared with coal and coal dust, has already improved the lighting of the pits considerably.
Dr T. Lister Llewellyn, the authority on nystagmus, dealt with this phase of the question very informatively, and his desire is that, other things being equal, mining engineers should choose a dust with high surface brightness. It will be a very great achievement if this stone dusting of mines, not only prevents coal dust explosions, but also reduces the incidence of a very painful occupational disease.