Subsequent to the joint inquest and inquiry into the causes and circumstances of the explosion which occurred at the Harrington No. 10 Mine on 9th December, 1946, the Commissioner, Sir John Felton, asked me to make a detailed examination of the above fan and the two broken belts, and consider whether the fan was running or stopped when the explosion occurred.

I examined the fan at the S.M.R.B. Station, Buxton, on 14th, 19th and 20th March, 1947, with the following results :–

(1) This 478 mm./18.8 ins. DIA/11/M.P. Aerex Fan made by Walker Bros. (Wigan) Ltd., is fitted with a 3.5 ins. diameter pulley having grooves for six V-belts. The pulley is enclosed by a steel inlet fairing which is cut away on one side so that normally there is sufficient clearance for a drive of six V-belts from a 5.1 in. diameter pulley fitted to a 10 h.p. electrically driven motor.

Although provision had been made for six V-belts, the pulleys contained only two belts in the second and third grooves respectively. (No. 1 groove is nearest to the fan, i.e. on the right-hand side of Plate 1.) But as two broken belts had been found in the bottom of the fan inlet after the explosion, it would appear that there were four belts on the pulleys prior to the explosion, and that these belts occupied Nos. 2, 3, and 5 grooves (this was confirmed on 9th April, 1947 by Messrs. Millar and Pattinson, who said that the drive consisted of four belts in the above grooves).

Each of the four belts was of the same type (A.60) and had been supplied by F. Wigglesworth. The lengths of the two broken belts were 5 feet 0¾ inches and 5 feet 1 3/8 inches, whereas the lengths of the two unbroken belts were 5 feet 2 1/8 inches and 5 feet 2 3/8 inches. The former belts were much darker in colour than the latter and may not have been out of the same batch or put on at the same time.

PLATE 1. View of part of damaged fairing, fan pulley and the two belts in Nos. 2 and 3 grooves.

PLATE 2. View of ends of the two broken belts which occupied Nos. 4 and 5 grooves prior to the explosion.

(2) The steel inlet fairing had been so damaged and displaced that it did not provide sufficient clearance for a drive of six V-belts; Plate 3 shows that it was impossible to put belts in the sixth and fifth grooves. It was possible to put a belt in the fourth groove, as shown in Plate 4, and it will be noted that the fairing is touching and slightly deflecting the belt, but this did not prevent the fan from being run with a slight scraping noise. Although I feel it was improbable, but not entirely impossible, for the damaged fairing to cut the belt in the fifth groove if the fan was stopped, I consider Plate 4 shows quite conclusively that it was impossible for the fairing to cut or cause the belt in the fourth groove to be broken if the fan was stopped.

In my opinion the two belts in the fifth and fourth grooves respectively were broken when the fairing was damaged and forced inwards while the fan was rotating at a speed sufficiently high to induce an excessive pull in the belts at the instant they were subject to interference and nipping on the slack side.

(3) As external examination of the inlet fairing indicated that the most severely damaged portion had been forced into contact with something inside it, I decided to take the fairing off for internal examination. This revealed that the fairing had contacted the nut holding the fan pulley in position and that there were rubbing marks on the nut and on the inside of the fairing. In order to prove whether the rubbing marks were caused by running the fan at Buxton or Harrington, it was essential to determine if the fairing and the nut were in contact. A special measuring apparatus established that there was a clearance of 0.033 inch between the fairing and the nut, thus proving that the rubbing marks had not been caused by running the fan at Buxton.

I consider that the rubbing marks on the nut and on the inside of the fairing were caused when the fairing was damaged and forced into contact with the nut which must have been rotating, and that the fairing then sprang back to give the clearance of 0.033 inch.

The damaged fairing and the rubbing marks are shown in the following Plates :

PLATE 5. Front view of fan, belts and fairing, showing the damage and variation in the depression caused by the rotating nut.

PLATE 6. Side view of fairing showing damage and variation in the depression caused by the rotating nut, and reduction of clearance for belt drive.

PLATE 7. Inside view of fairing, showing damage and bright rubbing marks caused by the rotating nut.

PLATE 8. Front view of fan pulley and nut, showing bright rubbing marks on the rotating nut.

(4) The inlet end of the fan is fitted with a detachable ring which normally contains four adjustable louvres for regulating the air supply. The first or bottom louvre was in position and slightly damaged, but the other three louvres were not attached to the ring. The connecting links were not attached to the first, second and third louvres, but a connecting link was attached to the fourth louvre.

The fourth or top louvre had been slightly damaged and apparently forced out of its bearings, and it could not be put back without dismantling the bearings. The third louvre had been bent inwards, towards the fan, until its shaft had come out of the bearings.

The second louvre had been severely bent inwards, towards the fan, and the ends of its shaft were many inches short of fitting in the bearings. On the top and bottom centre line of this louvre there were two local depressions, one of which could have been, and was probably, caused by one of the connecting links.

As the other local depression in the second louvre matched the general configuration of the damaged fairing, and as the length of the major depression in the fairing is practically the same as the length of a link connecting two louvres, I consider that the fairing was damaged by a connecting link and the second louvre, which were forced inwards by the explosion and projected on to the fairing.

(5) The above examinations were summarised and further tests made on 9th April, 1947, when the following persons visited the S.M.R.B. Station, Buxton

After examining the fan and checking all the factors, they said the examinations and tests indicated that :–

As Messrs. Millar and Pattinson felt it was possible that the rotation of the fan had been caused by the explosion, it was suggested that the fan should be fitted with speed recording apparatus and subjected to an explosion in the large gallery at Buxton.

(6) Since the above meeting I have carefully reviewed the results of the examinations and tests, and my conclusions are given below :–

A. E. CROOK.

30th April, 1947.