No.63. Tamworth. ([Fig. 30.])
November 20th.
none injured.
Fig. 30.
Revolving Steam Chamber, 12ft. 6in. long, and 5ft. diameter, 12 lbs.
The manhole was large, to facilitate filling and emptying, and was rectangular and unstrengthened on the edges, and measured 3ft. 6in. in length, and 1ft. 6in. in width, and the lid fitted on the inside and was held by clamps.
The boiler was much out of repair, and a crack shown in sketch, from one corner of the manhole to the commencement of the hemispherical end was only temporarily prevented from leaking by a screw-patch, which did not restore the strength.
The explosion happened when in revolving, the manlid was downwards, and the lid was driven nearly through the floor, and the shell was rent from opposite corners of the manhole, and blown through the roof.
The large manhole cut away nearly all the strength on one side, and the fastenings of the lid were not contrived to compensate at all for the loss of strength. The constant strain when revolving, also tended to weaken it. These two causes together were sufficient to account for the explosion, at the usual working pressure of 12 lbs., although it is possible that it might have been increased to 35 lbs., as that was the pressure in the boiler supplying the steam, although the pressure was regulated by a check valve.