50

MODERN STEAM PRACTICE.

the batten and above at the other end, and loosened it when thestrain came on. The pressure was noted as before; at 60 lbs. pres-sure the feed-pipe began to leak, the end bulging out -jJj- inch. At80 lbs. the feed valve joint leaked very much, and the longitudinalseams of the shell began to exude water; at 90 lbs. the south or right-hand flue began to crack, as if giving way; at 95 lbs. one of the jointsof the shell, and the first rings on the crown of the boiler, commencedto spout water, and the pressure could not be kept up, the leakagebeing equal to the supply of the force-pump. The joints of the feed-valve were then tightened, and also some parts of the shell caulked,the right-hand flue being found to be very much flattened. Thepressure was again put on, but it could not be got higher than80 lbs., as the flues had given way so much as to allow the water toescape by the fracture as fast as it was pumped in; so that thehighest pressure attained was 95 lbs., and this pressure had so injuredthe joints and flattened the flues as to render further experimentimpossible. According to Fairbairn’s rules the bursting pressure ofthese boilers was about 300 lbs. on the square inch, yet they failedwith one-third of this pressure. When the boilers were broken upthe plates were very brittle; indeed, so much so that it was a diffi-cult matter to get strips for testing. The rivets had likewise deteri-orated, and the heads flew off when the plates were struck with ahammer. The test strips gave the following results:—Shell in thedirection of the fibre, 197 tons; across the fibre, 1932 tons; whileGlasgow best plates is 24x34 tons in the direction of the fibre, and21'8 tons across the fibre. Furnace plates, direction of fibre, 17'1tons; ditto across, 15*3 tons. It will thus be seen that the mean ofthe shell plates is I9’45 tons, and that of the furnace i6'2 tons.Thus the furnace plates had deteriorated or weakened from 227tons to i6'2 tons, while the shell had weakened from 22^92 tons toI9‘45 tons. Now this is after the boilers had done duty for nineteenyears; so we are of opinion that sixteen years is quite long enoughfor boilers similarly constructed to be in use: and we trust otherfirms will follow Mr. Carmichael, so that this all-important questionof the deterioration of boiler plates that have not shown the slightestSymptom of corrosion, as in these boilers, may be finally deter-mined, with different qualities of plates.

In recording the testing of another old steam boiler, Mr. Car-michael States, 1 “ The result of the test so nearly coincides with that

1 See Trans. Inst, of Engineers and Shipbuilders in Scotland^ vol. xxii.