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Colliery Engineering

March, 1937

Shotfiring

Most of the evidence was directed to shotfiring practices and malpractices in 14's district, and Sir Henry draws the conclusion that in a number of respects little regard was paid, either by officials or workmen, to the requirements of the Explosives in Coal Mines Order. According to their evidence, there were many workmen who not only saw the deputies and shotfirers breaking the law but also assisted them in their offences. In such circumstances it was not likely that they would draw the attention of the Inspector to these malpractices. Whilst officials who do not obey the regulations have no excuse, workmen who aid and abet those officials cannot be held to be free from blame. They first take part in law-breaking and then after an accident occurs turn round and blame those with whom they have acted in collusion.

Sir Henry refers to the practice of using gumming for stemming the shots, and thinks there can be no doubt that the "gumming" contained coal and coal dust, but whether or how often to a degree violating the letter of the Explosives in Coal Mines Order (Clause 2 (b)), that "only clay or other noninflammable substance shall be used for stemming," he is unable to say.

With reference to the number of shots fired, says Sir Henry, the figures prove beyond question that on frequent occasions, and in some instances regularly, some of the deputies and shotfirers in all districts of the Dennis Section except perhaps 20's and 61's fired more shots per shift than they could possibly have fired with proper care and proper attention to the requirements of the Explosives in Coal Mines Order. Sir Henry's own conclusion is that, in the conditions prevailing in the Dennis Section, 40 shots was a reasonable shift's work for a shotfirer, and no deputy should have been allowed to fire any shots except on special occasions.

In general, he thinks it is desirable that deputies should not be called upon to fire any shots at all. Their duties should be supervisory only. Even in face of the tragic results of this explosion, it must not be forgotten that falls of ground account for about 50% of all reportable accidents in mines; it is far more important that the deputies should devote their energies and experience to seeing that the roofs and sides of the roads and workings are properly supported than that their time should be taken up with the firing of shots.

Sir Henry then discusses a breach of the Regulations against firing shots in a main haulage road by firing in 142's Deep between points X-Y (Fig. 2) on the inbye side of 14's level. While condemning this procedure in this instance, Sir Henry considers that the Regulations covering stonedusting have altered the position, and recommends that Clause 7 of the present Order should be amended so that on application being made to the Secretary for Mines permission may be given for shots to be fired on main haulage roads and main intakes.

Stonedusting

The material used for stonedusting the roads was a residue from the watersoftening plant installed at the surface of the mine.

There were about 16 tons of the dry material available for dusting purposes throughout the mine each week, and these, on the average, were distributed equally between the Dennis and the other sections of the mine. The output from the Dennis Section during the last ten full weeks prior to the explosion was 54,214 tons. On these figures, the amount of "stonedust" available in the Section, including any used in connection with shotfiring, was 3.3 pounds per ton of coal drawn. There was plenty of evidence to the effect that stonedusting was carried out, but there were irregularities in the taking of samples.

During the period June, 1930, to March, 1932, sampling of the dust was done not at intervals of one month but at intervals of six months, five months, four months and six months respectively. From March, 1932, when dust samples containing more than 50 per cent. combustible matter were collected in various parts of the roadways, until December, 1933, a period of 21 months, no samples of the dust on 142's Deep were taken and sampling of the dust on the Dennis Main was practically limited to a zone adjacent to the Dennis shaft bottom. After December, 1933, until the date of the explosion, samples were collected covering a longer length of the road, but there was still an interval of five months between the taking of samples, and none had been collected on the Dennis Main since May, 1934, and none on 142's Deep since June, 1934.

Hours of work below ground

Though no direct evidence as to the hours of work below ground was taken, there was a considerable amount of incidental evidence that men were allowed to work and did work longer hours than are permitted by the Coal Mines Regulation Act, 1908 — generally known as the Eight Hours Act — as amended by later Acts. In fact, the provisions of that Act were, to all intents and purposes, ignored.

It does not, of course, excuse breaches of the law to say that the men were willing to work overtime. But, in such a case, it does not lie with those representing the men to blame only the Management and the Inspectors. The question of preventing the working of illegal overtime is one within the power of the men themselves and their trade unions and Sir Henry regrets the increasing extent to which, of recent years, it has taken up the time of H.M. Inspectors and encroached on their proper duties of attending to matters directly concerned with health and safety.

Sir Henry then goes on to express his opinion that miners should be members of some effective trade union to enable any complaints regarding safety to be lodged without fear of victimisation.

Theories as to the cause of the explosion

It is often difficult to state the exact place of origin and the actual cause of an explosion even when inspection can be made of all the workings traversed by that explosion, but when, as in this case, no inspection is possible, the place of origin and cause become matters of conjecture not capable of proof and, as Mr. Joseph Hall rightly indicated in his speech, it is not possible to state the cause of this explosion.

Sir Stafford Cripps said that when one sorted out the whole mass of evidence and read it through, it became perfectly clear that the two danger points were 95's and 14's. In regard to 95's, because of the probability of a shot having been fired in 142's Deep at 24's airway and the possibility of that shot having ignited gas which had issued from the airway. And in regard to 14's, because of what he regarded as the clear evidence that there was present in the top end of the face a few hours before the explosion a large quantity of gas which he suggested might have been ignited by some mishap to a safety lamp or a coalcutter or some other mischance.

Mr. Charlton thought that, for reasons which he outlined, firedamp had come into and filled the drift which was being driven beyond the "Clutch" and on top of goaf laid down after 1918. He thought the gas had come out of the drift and was present to some extent next the roof in 142's Deep as far as a canch where the Deep crosses a fault; that the lamps of the men working in the drift and those at the "Clutch" had been extinguished by that gas; and that ignition was at the telephone, when it was about to be used for warning those inbye of the influx of gas in the drift.

Mr. Hartley Shawcross suggested that the explosion was one of firedamp alone and that coal dust could have played no part. He submitted that the explosion must have started somewhere in the neighbourhood of the "Clutch" or of 29's Turn and he supported Mr. Charlton's theory as a very probable one. Alternatively, he suggested that the explosion might have originated from spontaneous combustion at a pillar of coal lying in the goaf up against the 45-70 foot fault.

Sir Henry does not discuss the arguments for or against the several suggestions made as to the cause and the point of origin of the explosion, but looks with grave suspicion upon the circumstances existing in connection with 24's airway in 95's district.

General observations

Ventilation. — Adequacy of ventilation is not measured by quantity but by quality. Nevertheless, in addition to the requirement contained in Section 29 (1) of the Coal Mines Act, 1911, that "an adequate amount of ventilation shall be constantly produced in every mine to dilute and render harmless inflammable and noxious gases . . .", it would be an advantage to prescribe a minimum quantity per minute for each district of a seam relative to the output of coal per day or per week from that district.

Main Airways. — Section 42 of the Coal Mines Act, 1911, was enacted before the General Regulations of 1920, setting out the precautions to be taken against coal dust, were established, and Sir Henry expresses the opinion that instead of two main intakes in every seam it is desirable that two main return airways should be provided in connection with every main intake airway and that these main return airways should be placed one on either side of each main intake airway.

Reporting of Gas. — Some of the deputies said if they found gas and cleared it, they did not report it in their report books. All findings of gas should be reported in the statutory report book.

Underground Fires. — Fires occur in mines from other causes as well as from explosions, and it is desirable that means of fighting such fires should at all times be readily available. There seems to be no doubt that water under pressure is the best means of extinguishing a fire. At some mines water pipes are laid along all the main roads; it is a question whether they should not be required to be so laid in all main roads which are dry and are supported by material of an inflammable nature.

Precautions against Coal-Dust. — The General Regulations embodying the precautions to be taken against coaldust came into force on January 1, 1921. During the previous 15 years, 1,899 persons were killed in 231 explosions and during the subsequent 15 years 977 were killed in 187 explosions. The reduction in the number of deaths (hiring the latter period by nearly 50 per cent. may fairly be claimed to be due to the use of stonedust, but it may be asked whether some amendment of the Regulations would not result in a further reduction.

Road Dust Samples. — At some collieries a plan is kept showing the zones from which dust samples are taken. Such a plan should be required to be kept at every colliery ; the zones should be numbered and the sample taken from any zone should be numbered with the same number as the zone from which it has been taken and the result of the analysis of the sample entered in the dust record under that number.

(d) Management and Supervision. — As regards the general management and supervision of the mine, the average killed and injury rate per 100,000 manshifts worked at Gresford Colliery, during the five years ended December 31, 1933, was lower than the rate for the remainder of the mines in North Wales and the rate for Great Britain; and the fatal accident rate at Gresford, on the same basis,, was almost 19 per cent, lower than that for either North Wales or Great Britain.

Sir Henry thinks it is a mistake to work large collieries without some able mining engineer in authority and superior to a manager, known under the Act as "Agent." The person appointed to such a post needs to be of strong character and able if necessary to resist those in control of the commercial side of the concern. Sir Henry has an uneasy feeling that Mr. Bonsall was overriden. Why was the driving of 37's place stopped and the men sent to produce coal? Why was 105's drift not being worked continuously on all three shifts? Why was the scouring in 14's stopped instead of being pushed on continuously ? Why were men taken out of 14's return airway to work on the coal when there were absentees in the face? And, above all, why were not 29's, 14's and 95's districts stopped until the necessary alterations had been made in order to provide adequate ventilation ? It may be that Mr. Bonsall was incapable of seeing the position as it existed, but Sir Henry feels sure that Mr. Williams, the Undermanager, saw it. But what could he, — a newcomer — do ?

Inspections on Behalf of Workmen. — Sir Henry is of opinion that all persons working underground in a mine should be members of a Trade Union and, for their own satisfaction, should take advantage of the provisions of Section 16 of the Coal Mines Act, 1911, and have inspections made at intervals of not more than three months.

Mines Inspection Divisions. — Sir Henry has always considered that the incorporation of two Mines Inspection Districts, as they existed before June 1, 1910, in one Division was a mistake and, so far as has been possible, he has tried to correct that mistake. "The actual visiting and inspection of mines and quarries form by far the most important part of the duties of an Inspector" according to the Instructions issued to the Inspectors years ago by the Home Office, yet the present unwieldy Divisions were created. Sir Henry thinks for the better administration of the Act and to enable the Inspectors to discharge "by far the most important part of their duties," a reversion to the original position should be made. By so doing, the Inspector in charge of each district would be able to become familiar with the workings of the mines in his District, a position which at present, except in one or two smaller Divisions which need not be altered, is not possible. And there would be no division of responsibility which now, with Divisional Inspectors and Senior Inspectors, exists. Each District Inspector would be in charge of a District and would know that he, and he alone, was responsible for it.

Drawings accompanying the article