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Colliery Engineering

March, 1937

REPORT BY SIR HENRY WALKER

The main Report is given by Sir Henry Walker, and his comments will now be summarised.

Ventilation

Ventilation of the mine was produced by a double inlet Walker fan placed at the surface and steam driven. There was no proper air-lock at the top of the upcast (the Martin) shaft, platforms (butterfly boards or policemen), raised by each of the two cages as it came to bank, being relied upon to prevent air flowing direct from the surface to the fan.

The air measurements, said to have been made monthly, as required by Section 29 (2) of the Coal Mines Act, 1911, were entered in the prescribed book, Mines and Quarries Form No. 37, to June 30; the measurements said to have been made in July and August were found in the note-book of the Assistant Surveyor (William Idris Cuffin), who said he made the measurements. Some 18 months later — in June, 1936 — Mr. Cuffin, when giving further evidence, said that on the instructions of the Manager he had not in fact made any measurements since June, 1934; that the figures in the note-book for July and August were imaginary and that he had concocted them because the Manager had told him to do so a day of two after the disaster.

The intake and return airways in the Dennis Section of the mine are shown in Fig. 1. The point of measurement in the Dennis Main intake airway is shown at M1 and the points of measurement of such splits as were measured are shown at M3 and M7. Contrary to the requirements of Section 29 of the Coal Mines Act, 1911 (and No. 77 of the General Regulations dated July 10, 1913) the quantity of air was never measured in certain splits, namely those coursing along 81's and 14's levels.

In regard to measurements required to be made in each ventilating district at or as near as practicable to a point 100 yards back from the first working place at the working face which the air enters, the only such measurement said to have been made was at M7 in 61' s district. Sir Henry Walker points out that another similar measurement should have been made in 109's district. The measurement said to have been made at M7 in 95's district was not strictly in compliance with this requirement; if the air had in fact entered 24's airway from 142's Deep, it should have been measured actually in the airway. Whether measurements 100 yards back from the first working place in the other districts are required by the Regulation Sir Henry regards as not at all clear.

Sir Henry does not believe that many of the measurements recorded even in the prescribed book were ever made. In Mr. Cuffin's note-book were entered the velocities and areas at the various measuring points for November, 1933, January, April and June, 1934. But for November, 1933, there is only one entry in this note-book referring to the Dennis Section, namely a measurement at Ml; in January, and again in April there are only two such entries, namely measurements at M2 and M5; and in June there are five entries, namely, measurements at M1, M2, M3, M4 and M5.

On June 8, 1936, during the sitting when he confessed that the figures for July and August were fictitious, Mr. Cuffin was asked where the calculations not appearing in the note-book were. He replied that he did not always use a note-book but used foolscap. Sir Henry does not accept that explanation. He thinks Mr. Cuffin was given more work than he could overtake and that in consequence he scamped the work of air measurement. When examining the figures in the note-book, Sir Henry found that there were errors in the calculations — in some cases the entries in the prescribed record being 10,000 cu. ft. per min. too little, and in the prescribed book itself there were errors in simple addition. Some of these figures, Sir Henry states, cannot be accurate; for example, in January they represent that 26.305 cu. ft. per min. or 57% more air was coming out than was going in, whilst in June 425 cu. ft. more were going in than were coming out.

Turning to the more specific evidence afforded by the statutory reports of the deputies, it was regrettable, the Report states, that the evidence available did not include all the reports made by the deputies from the beginning of 1934. Some of these reports could not be produced, the hooks in which they had been made, or copies of them, not having been kept in the office at the mine, contrary to the provisions of Section 24 (1) of the Coal Mines Act, 1911.

Ventilation of 20's, 61's and 109's Districts. — Evidence is summarised as to the ventilation of No. 4 North Section, comprising 20's and 61's districts, and of 109's district, and it would appear that the ventilation in these districts complied with the crucial requirement of the Coal Mines Act, 1911, namely, that the ventilation shall be constantly of an amount sufficient to dilute and render harmless inflammable and noxious gases.

Ventilation of 95's District. — The ventilating current for this district entered at the point marked M7 in Fig. 1 and left by the road which, at its upper end, joined 14's level. Two or three yards on the inbye side of the point M7, according to the evidence of some witnesses and as shown in Figs. 1 and 2, the current was split, one part continuing down 142's Deep whilst the other turned into a road on the left (North-West) known as 24's airway. According to Sir Henry's Report, the evidence as to whether in fact 95's district was ventilated in this way was contradictory. During the first day of the Inquiry when examining the Manager, Mr. Charlton threw doubt on there being, in fact, any such splitting of the air current. Conflicting evidence was obtained from numerous witnesses as to whether 24's airway was fulfilling its intended function or whether it was acting as a return, and in any case it appears that the mouth of this airway was blocked up a fortnight before the explosion. Sir Henry states that he has no difficulty in making up his mind which of these two bodies of evidence is correct. The temperature of the air passing on 95's face was much higher than the temperature on 142's Deep; there was no positive means of any kind to reverse the flow according to natural laws, and there is no doubt that such air as did circulate on this side of the district left 142's Deep at 95's road, passed down that road to 95's face, up that face and out along 24's airway on to 142's Deep again. In other words, there was a local circulation due entirely to natural causes as Mr. Charlton had suggested, the main air current simply passing down 142's Deep and out by the return to 14's level.

Conflicting evidence was also obtained as to the presence of gas in 95's district, and especially in 24's heading. Sir Henry finds it impossible to reconcile the evidence of the Under-manager, that the heading had not been worked at least since January 21; the Manager, that there was a little gas in this heading when it was worked; the deputies' reports of gas in it only from January 21 to February 3 and on May 2 and 3; the night shift Overman's statement that he found a "little bit" in the top end of the heading in March and that the heading, although shown in Fig. 1 to be about 35 yards long, was then only 3 or 4 yards in length. Sir Henry is unable to accept the evidence of these various officials in certain respects, and in examining the evidence of the deputies concluded that in their inspections they did not travel 24's haulage road, as they were required to do. The evidence of certain other witnesses corroborates that of the officials to the effect that there was no danger from gas, but that of several of the colliers points to the workings being unduly hot, especially during the week or two before the explosion, and to the mouth of 24's airway being stopped up. In particular, John Taylor, ripper and contractor, stated that he had knocked a hole through near the mouth of this airway and his lamp had been extinguished by gas. He realised that conditions in this district were dangerous, and he had reported to Matthias, a deputy who was killed in the explosion, but had not taken the matter further for fear of victimisation. Bert Jones, collier, stated that he was in 24's heading with Mr. Bonsall, the Manager, but could not get within 10 yards of the face because his lamp was blazing up.

The position on the left side of 95's district, in Sir Henry's opinion, was precarious, and, whilst it would have been eased if the drift (105's) which was being driven to the dip from 81's haulage road had been holed into 24's heading, work having been stopped in 24's in the meantime, it would not even then have been satisfactory and would not be until a separate main return airway on the left side of 142's Deep and of the Dennis main haulage road had been made. Add to the position in regard to the ventilation of 95's district the firing of shots at the mouth of 24's airway, and the whole situation became one of great danger.

Ventilation of 14's District. — The air for the ventilation of 14's district was that which had already been round 95's district, together with an unknown quantity which passed from 142's Deep along 14's level. These two currents met on 14's level at the point where the return (147's) from 95's entered that level; thereafter they travelled as one current up the belt conveyor road and thence on to the bottom end of 14's face by way of a crossgate to the left. The air then passed along the face and, at the date of the explosion, out by a road known as the old timber road. Until June, 1932, the district was part of 109's but thereafter had been left unworked until December, 1933. During the last week of November, 1933, two doors in 14's level were removed and, after the necessary repair work had been done, work was resumed on the face as a separate district — 14's district — in December, 1933. By March, 1934, the face had broadened out with the rise end marching with the goaf laid down in December, 1929, and with a road made through that goaf to the main return as the district return airway. In April, the first of a series of falls occurred at the rise end of the face and in each case blocked this district return airway which, as will be seen from Fig. 3, skirted a fault. The fall in May (May 24), which extended for 47 yards, resulted in the abandonment of the district return airway, as originally planned, for a scheme which brought in two roads, one known as the old timber road and the other old 23's in 14's, and a third as a connection from the latter to old 3's conveyor road. That part of the face which remained open to the rise of the old timber road was divided into two by a brattice, the face beyond the fall being and thence outbye to the 75 ft. fault

By this route the return air had to travel downhill to within four yards of the intake and the old roads comprised in the return had to be repaired, the repairs in the road connecting old 23's in 14's to old 3's conveyor road and thence outbye to the 75 ft. fault being started on June 25, a month after the fall on the face had occurred, and completed on September 15. This route continued to be the return airway until September 1, when a further fall at the face occurred and again that airway was blocked. The length of face lost by this fall was abandoned and the old timber road, which towards the end of June had been turned to the rise with the intention of cutting out the then existing return, became a return throughout its length. The course described at the date of the explosion is shown in Fig. 3, which was made from descriptions given by officials and workmen at a sitting held to elucidate the matter so far as possible.

The disadvantages of the course resorted to after the fall on May 24 were evident, and to mitigate them a scouring through the goaf was started in July from the old timber road with the intention of cutting out the loop at the low end. This scouring, which should have been pressed on with vigour, was started in July, stopped about the middle of August and fenced off. A scouring from the original return was then started to hole into the scouring from the old timber road but at the date of the explosion a holing had not been made. The Manager did not know whether or not the scouring was going from both ends just prior to the explosion and he made no inquiry.

The measures taken to provide an alternative district return airway after the first was lost in May, 1934, were, in Sir Henry's opinion, dilatory and unsatisfactory, and it was not proper to continue to work 14's face until a connection direct to the main return airway had been made. At the time of the explosion, and for several months previously, the general layout of the ventilation was bad.

Sir Henry Walker then refers to a matter in which he considers that important information was withheld from the Court of Inquiry by certain witnesses. In May, 1936, it became known to him that at some time in May or June, 1934, a door or doors had been placed. in the No. 4 North return airway near the air measurement station marked M.5 in Fig. 1. This was a new development which was the subject of examination at a sitting of the Court of Inquiry on June 8, 1936. when it was found that doors with a space of about 1 2 inches at the foot had been erected near the point mentioned at the end of May, 1934. These doors were not shown on the ventilation plan or on the general plan produced at the earlier sittings of the Inquiry during which it had been sworn by the Manager and by the Under-Manager that there were no regulators in the Dennis Section of the mine. Why such evidence should have been given, Sir Henry comments, it is difficult to understand unless it be that it was desired to hide the lack of a sufficient quantity of air in 14's district. Apparently the fall on 14's face on May 24 had made it imperative that more air should be forced into that face, and to try to attain that end the regulator doors were erected in No. 4 North return. Unfortunately this step, which was a natural one to take, did not have the desired effect, and it is probable that it chiefly resulted in causing more air to escape from 142's Deep into the return leading from 14's district to 29's through the doors placed across 29's haulage road.

But whatever may have been the quantity of air which passed into 14's district and whether or not it was increased by putting the doors in the No. 4 North return airway, by no means all of it reached 14's face. There were leakages, and, Sir Henry considers on the evidence, substantial leakages at places along the roadway.

Sir Henry Walker then examines the evidence as to the occurrence of gas on 14's face, and concludes that at times, and not infrequently, the ventilation of 14's face was inadequate and that in consequence gas, which was not reported by the deputies, accumulated more particularly in the top end; and he regards, as corroborating this conclusion, the fact, and the concealment of the fact, that doors were put in the No. 4 North return airway in May or June, 1934.

Referring to the fall on May 24, he considers that the position before that fall occurred was unsatisfactory and could only become worse as the face was taken further to the rise. After that fall, the position was so precarious that drastic remedies were needed and should have been taken.

Ventilation of 29's District. — Apparently 29's district was ventilated by the return air from 109's. 95's and 14's districts but really by that return air together with an unknown quantity which left 142's Deep at 29's Turn and leaked past the three doors placed across 29's haulage road — see Fig. 1. It was no doubt due to this large leakage of air into 29's district that the witnesses called were able to say that the ventilation in 29's was good or very good and that they had been little troubled with gas. But this adventitious aid to the ventilation of 29's was at the expense of the ventilation of the inbye districts of the mine which was dependent upon the condition of the three doors in 29's haulage road and the steps taken to see that they were not all open at the same time.

General Remarks on Ventilation. — Apart from the verbal evidence, examination of the ventilation plan shows :–

(1) That No. 4 North District (20's and 61's) got first pull at the ventilation, and as it was being coursed in that district on natural lines it was unlikely that any great difficulty would be experienced.

(2) That 109's district was in a somewhat similar position though, in view of the faulted ground in the middle of the district and the bend in the return airway. not so favourable.

(3) That there was no outlet at the rise end of the left side of 95's district.

(4) That the faces of 14's district and of 29's district were going to the rise, and

(5) That the same split of air was being coursed round 95's, 14's and 29's districts and at the return end in 14's and 29's had, in each case, to come a considerable distance downhill.

(6) That between the point M.1 and the points M.3 and 4 there were likely to be substantial losses of air by leakage — notably into the haulage road from 29's district, this explaining why the ventilation of 29's district was not so bad as, on primary considerations, it should have been.

Because of these leakages and of the prior pull on the air taken by the No. 4 North district there could have been only a comparatively small quantity of air for the ventilation of 109's, 95's and 14's districts, and keeping in mind the lie of these districts, it was to be expected that 109's district would get more of that small quantity than 95's and 14's and less trouble be encountered in that district than in the other two.

In view of the small quantity of air passing M.4 and in consideration of the depth of the workings from the surface, so small a current would in its passage round the workings become very heated and its being hot would add greatly to the difficulty of ventilating workings going to the rise, such as 24's place in 95's district and the whole of 14's face.

For the reason why the scheme of ventilation in the Dennis Section had got into such a position, it is necessary to go back 12 to 15 years to the time when the three main roads — the Dennis Main and the roads parallel to and on either side of it — met the downthrow fault to the North East of the "Clutch."

Apparently it had been the intention to maintain these three parallel roads and, after workings had been opened out on the dip side of the fault, it was still intended to maintain return airways on either side of 142's Deep. But when a further fault was met — this time an upthrow — only the return on the South side of 142's Deep was put through it. That on the North side was abandoned, and no proper consideration was then given to the problem of ventilating any subsequent workings beyond that upthrow fault.

But even if a return parallel to and on the North side of 142's Deep had been maintained, the method of working 29's district, involving the use of doors across the haulage road into that district, would still have resulted in considerable leakage of air at 29's Turn. This difficulty was the result of the failure to drive the Dennis Main road and the roads on either side of it through the downthrow fault North East of the "Clutch," and this failure was the initial cause of the unsatisfactory scheme of ventilation existing at the time of the explosion.

Had these three roads been driven through that fault and the seam then developed to the East and North East, there would have been no difficulty in providing separate splits of ventilation for each district. Whether this lack of vigour was due merely to dilatoriness or to lack of funds it is not possible to say, but on this point the Manager, in evidence, in answer to Mr. A. T. Miller, said that in the matter of finances, moneys required by him for upkeep and maintenance, there had been no stint whatever and there was no foundation for the suggestion that he was working under undue pressure to produce output.

Be that as it may, work was being carried on in face of excessive leakage of ventilation, but so long as the lie of the workings allowed such air as was available to take a natural course, the workings were kept clear of gas. As soon as an attempt was made to course heated air downhill, however, then trouble began and, in addition to that natural difficulty, there came the falls on 14's face.

So long as 14,s face abutted on the return, the ventilation, which in the deeper workings of the mine was most probably due to natural causes alone, was sufficient to carry away the gas, but so soon as the air on that face had to be brought downhill, difficulty arose, and when, after the fall on May 24, the return air had to be brought right away back to within a few yards of the intake, the position became so precarious that drastic remedies were needed and should have been taken.

Work on 14's face should have been stopped altogether until a return air course, far removed from the intake, was made.

Work on 95's and 24's faces should have been stopped until the place (105's) being driven to the dip from 81's level had holed, and, in order to get more air into the inbye districts, 29's district should also have been stopped and the leakage of air direct into the return by way of 29's Turn prevented.

These seem drastic remedies but even had they been taken, there would still have remained the initial error, and, until it was repaired, the position would not have been entirely satisfactory.

Sir Henry Walker refers to General Regulation No. 11 against wafting out gas, and considers that blowing gas away by compressed air does not contravene the Regulation.

With regard to airways the Manager said that the day-shift deputy in each district was appointed to examine the airways at least once a week in accordance with the requirement of Section 66 (d) of the Coal Mines Act, 1911. Of some of these examinations, the reports required by the Section to be made were not made. This omission the Manager said was due to the fact that the deputies concerned examined the particular airways daily and the result of those examinations was included in the reports made daily. This explanation is not valid for all the airways, for example 14's and 29's, and in any case the reports should have been made in the appropriate book.

The size of the return airways generally was at the date of the explosion, according to the evidence, greater than it had been for some time. 109's return had been repaired throughout; 14's new return was completed a week before the explosion occurred, and 29's had been repaired as far as the bottom of the drift through the 75 ft. fault at the inbye end of the Main Martin Return. But all the return air from 109's, 95's and 14's and 29's had to pass up this drift which, at one part where there were three ladders, was only, according to one witness, 4 ft. by 4 ft., according to another, 5 ft. wide by 3 ft. high — a very small area for a main return airway.

Drawings accompanying the article