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Extracted from the Annual Mines Inspectors Report for 1876

Report of James Willis (page 244)

By Boilers bursting.

One boiler exploded during the year, by which two workmen lost their lives. At the inquest held on the bodies, Mr. Graham, the coroner, had secured the services of Mr. William Waller, an engineer well known for his knowledge and experience in all matters relating to steam boilers, who produced a report for the guidance of the jury. The following is the report alluded to, and it will be easily understood by referring to the plan accompanying it. I agree with Mr. Waller that the original form of the boiler had not been maintained in the repaired portion, but I do not think the shape had been altered to the extent spoken of by him. I have no doubt, however, that a great strain had been put upon its original portions by the manner in which the new portions had been built in; and this to my mind, together with several cracks in the plates over the fire, repaired by the almost, I hope, obsolete plan of putting in large-headed rivets, the thinness of some portions of the plates, and the great age of the boiler, were quite sufficient to account for its destruction. There did not appear to have been any lack of attention on the part of those in charge, but there did appear to be evidence of undecided responsibility as to repairs, &c. The mountings were not of modern design, and the openings, such as man-holes, hand-holes, &c, were not strengthened in any way as they should have been. The destruction of the surface erections and fittings caused by the explosion was most complete; so much so, that the second shaft could not for several hours be made available for drawing the large number of men who were in the pit at the time. They were, however, well attended to by having food sent down and otherwise made as comfortable as circumstances would permit. The jury before whom the inquest was held added the following recommendations to their verdict:— "That there should be an improvement as to the inspection of the boilers; that where repairs were necessary, properly qualified persons should be employed, not only to see that such repairs were necessary, but to see how they were to be executed, as the present mode was unsatisfactory and insufficient."

Mr. Waller's Report.

"Boiler Explosion at Kibblesworth Colliery.

"28th November 1876.

"From my examination of the wreck of this boiler on the 30th November, I was enabled to form an opinion as to the cause, but was prevented from getting a confirmation of the conclusion arrived at until the large piece of the boiler which fell in the field had been raised and turned over. One side was cleared from the ground on the 6th December, and the whole of the piece was exposed and turned over on the 8th. Two detached plates were directed to be brought for the examination of the jury in explanation of the remarks hereafter.

"There were five boilers in the range, numbered from the winding engine-house, Nos. 1, 2, 3, being in connexion with one chimney, and Nos. 4, 5, with another. The No. 1 boiler had been turned with the front end up and against the engine-house, and then backwards and to the right of its seat. No. 2 was the boiler which exploded, and No. 3 was under repair at the time of the explosion, and was therefore empty. It had been thrown upwards and to the left hand, and rather forwards, and had been turned round. The seating of No. 4 was also injured, and the chimney for Nos. 1, 2, 3, thrown down.

"The No. 2 boiler is stated to have been about 20 years old, made by Messrs. Joicey, of Forth Banks, Newcastle, for one of their own collieries, but transferred to this colliery on completion. It was plain cylindrical egg-ended, about 30 feet long X 6 feet diameter, made of ten strips of plates laid longitudinally to form the circumference, and of four plates in length in the alternate strips, the others being of three plates and two short lengths, as were the top and the side lengths upon which the knees were. The ends were made of 10 taper plates, with one closing plate 3' 6" diameter.

"The boiler mountings upon this boiler were as under, and in the order from the front:—

1. Alarm whistle to indicate low water, with float to regulate the working of the same.

2. Dead flange.

3. Open safety valve with lever and weight.

4. Steam jug ; valve open.

5. Feed jug, not self-acting; a little open.

6. Float standard, pulley, and wire.

7. Float standard, pulley, and wire with low-water whistle attached.

8. Sludge gland.

9. Closed safety-valve.

"There were thus three low-water indicators on the boiler, two being visible, and two audible; and with these appliances it would appear unreasonable to expect that any deficiency of water would escape immediate observation, and as the flue line was at the middle of the boiler, and the usual water level from 9 to 12 inches above this, there was considerable margin for safety. The plates themselves bear no indications of there having been shortness of water; so there is ample evidence, though negative in character, that there was sufficient water in the boiler at the time of the explosion.

"The front safety-valve was 4½ inches diameter, with lever 3 feet 5½ inches long, fulcrum 4 inches, and weight 52 lbs., representing the pressure on the boiler as 36 lbs.; and on trying the action of similar valves on Nos. 4, 5, boilers (on 6th December) the valves blew at that pressure, thus confirming my calculations.

"Effects of the Explosion.

"The boiler was rent by the explosion into seven pieces, one of which was again broken by striking the ground; this was the greater portion, about three fourths, of the back egg-end, which was thrown to a great height, and fell a little to the right of the line of the boiler and about 60 yards behind its original position.

"Another piece, part of the front egg-end with parts of four shell plates attached, appears to have carried away the head gear of the pit, and was lying on the pit heap in front, and nearly in a line from its original seat.

"The front portion of the shell and a small detached piece were lying near the railway; while in the field and lying at about the same distance from the bed was the main portion of the boiler with the back end, and under this were two plates, which will be referred to again as L and M, which most likely were broken away from the main piece by the violence of the tall. The whole of the boiler had been projected to a considerable height, and had there parted, falling to the right-hand side and in front of its original position.

"The direction taken by the several parts would indicate that the rupture took place near the bottom, but rather to the left-hand side of the vertical centre line, and behind the middle of the boiler's length. Following this view, and as the boiler had broken in the middle of its length at the bottom seam, it became necessary to have the large piece in the field raised and turned over in order to follow the lines of fracture, and though at the time of this examination it had been lying in the ground for a week (6 and 8 December), there were sufficient indications upon the piece first raised, and in the seam I, J, K, to prove the correctness of this opinion; and upon the further examination, the whole of the fractures being exposed, and the plates L and M found under the large piece, it was thought desirable for them to be presented before the jury that they might form their own opinion as to the correctness of the conclusions arrived at. The plate L is that to which the sludge pipe was attached, and M is the back plate of the bottom strip.

"The plate L shows marks of old fractures along the left-hand side of it, and this formed part of the seam I, J, K, before named, from which the cross seam in the bottom plate, at which the two pieces separated, passed at right angles; this is the seam in which on the left-hand side of the boiler there was a length of nine inches showing recent fracture, and 13 inches (at H) of old crack, pointed out to the jury. On the other side of the seam I, J, K, is a plate which is hard and brittle. These plates, already referred to as forming part of the bottom of the boiler, are evidently the original plates. The lines of rent are shown on the drawing produced, so need not to be more fully described.

"Repairs.

"The front end of the boiler had been patched with the plates B, C, D, E, to within two feet of the middle, the piece A being one of the old plates. These patches had not been attached to the old rivet holes, but had covered part of three plates as shown, being of various sizes and shapes. There had been considerable caulking at the right-hand side of C patch plate.

"It will be readily understood that if a ring or series of rings be suspended at above the centre line (horizontal), and the bottom cut away, the weight of the ring will cause the opening to enlarge by the position of the suspense; so in this boiler, when the bottom strip has been cut out for repair, the new plate has been larger than the old, and this has evidently been discovered when E was put in 4' 7" wide, with pieces of plate 7½" and 9" at either side, making 5' 11½", so that it would not fit on to the circular seam of the front egg-end, and necessitated the insertion of the two plates F, G, to connect the new work with the egg-end as shown.

"Before proceeding further on this point it will be sufficient to mention that there is nothing to suggest shortness of water, but quite the contrary, that any sudden accumulation of pressure would have found relief at the safety valves, as four of the boilers were connected, and each was fitted with two safety valves. Then as to the plates, there was no plate in the boiler less than ¼ inch thick except at the egg-end in front and right-hand side plates, which were 3/16 inch, but these did not in any way contribute to causing the explosion. The quality of the plates used in the construction of the boiler is amply shown by the twisted pieces and short bends which are found without a crack in some places; while the shortness and brittleness of other plates may be traced to deterioration, as in that to the left-hand side of the middle cross seam in the bottom plate, and in the strip attached to the right-hand side of the plate L.

"In seeking for the cause of the explosion there are some facts apparent here which may have been overlooked in other cases, but which ought to receive especial attention. We will go back to the patches, and seeing that across the plate A and two side plates the measurement was 5' 8" before repair, the distance between the same seams at E would be the same, but instead of that we have the following figures:—

	Ft.	in.
Across the three plates at patch B	5	9
Across the three plates at patch C	5	9¾
Across the three plates at patch D	5	10½
Across the three plates at patch E	5	11½

or as measured by Mr. Thompson inside the plates on the ring seam at the front end 6 inches, so that, even allowing for the expansion of the plate, there would be 3½ inches gained in width of a horizontal strip of boiler in 10 feet, acting as a wedge to split up the seams behind in the deteriorated plates, and there can be no doubt that the fracture in the cross seam at H, and in the longitudinal seam at I and K (though it appears to have held at J for 3 inches, 7 inches in front of the cross seam to the left hand), and behind the cross seam, are due to the extra strain so thrown upon these seams by the careless and unskilful manner in which the repairs have been executed in plates of the age which these were, and deteriorated, though not thinned. The difference of 3½ inches is so considerable that it must have been known, as shown by the plates G, F, being inserted to cover the old ring seam and gather in the enlarged shell to 13 inches down the taper plates of the end, that I feel bound to say that the explosion is due to the absence of care and proper workmanship in setting out the plates for patches, and not seeing that the proper circumference of the boiler was maintained after, as before such repairs.

"9th December 1876."