EXPLOSIONS, BOILER. 



297 



of the boiler. This plate was perforated with holes 

 three sixteenths of an inch in diameter, at intervals of 

 eight inches, for the purpose of admitting the steam 

 from the water below gradually to the steam-space 

 above. This plate is Mr. Lawson's invention, and he 

 claims that it will prevent concussion in the boiler 

 when the steam is drawn off suddenly by opening the 

 throttle-valve, or suddenly cutting it off from the 

 cylinder, and thus insure greater safety in the manage- 

 ment of steam-boilers. 



The boilers used in making these experiments were 

 manufactured expressly for that purpose, and had 

 never been used before. The first boiler placed in 

 position for the test was the one containing the plate, 

 or "diaphragm," as it is called. To this boiler was 

 attached a three-and-a-half-inch steam-pipe, sixteen 

 feet in length, with a discharge-valve attached, six- 

 teen feet from the boiler. A steam-pipe four feet in 

 lenHh including two elbows and three and a half 

 inches in diameter, formed a connection between the 

 valve and a cylinder, the diameter of which was eight 

 inches and length four feet. 



A steam-gauge, with a pipe twelve feet in length, 

 was placed on the inside of a bomb-proof. From the 

 inside of this bomb-proof the discharge-valve was 

 operated by means of ropes. Fire was placed under 

 the boiler, with nineteen inches of water to start with. 

 When steam was generated, the discharge-valve was 

 suddenly opened at certain intervals, discharging the 

 steam into the cylinder. These operations were con- 

 tinued until the pressure in the boner had reached 225 

 pounds to the square inch, when the discharge-valve 

 was opened, and the material forming the joint be- 

 tween one of the cylinder-heads and the cylinder blew 

 out. The discharge-valve, at the same time, proved 

 too weak, and began leaking so badly that the test 

 had to be abandoned. This ended the first test, Feb- 

 ruary 17, 1882. The second test took place March 7, 1882. 

 This test was made with the plain cylindrical boiler, 

 and the discharge-valve, steam-pipe, and all other 

 outside attachments substantially the same as they 

 were with the other boiler during the first test. A 

 stronger discharge- valve, however, was employed, as 

 were also two new steam-gauges. The latter^ were 

 manufactured expressly for these tests by William 

 Kirkup & Son, of Cincinnati, Ohio. Fire was started 

 under the boiler, and steam raised slowly. At 12.02 

 p. M. the steam-gauge indicated 75 pounds. In four 

 minutes thereafter the pressure had increased 25 

 pounds. At this point the discharge- valve was opened, 

 and the needle of the gauge fell five pounds, but im- 

 mediately rose again to 100 pounds. From this point 

 the pressure increased to 125 pounds in six minutes, 

 when an attempt was made to raise the valve, but the 

 line broke ; the furnace-door was thrown open, and 

 the fire drawn. The line was repaired, and the lever 

 attached to the valve was lengthened, when the boiler 

 was again fired up. At 75 pounds pressure the valve 

 was raised, and the needle of the gauge showed the 

 vibrations recorded in the following table : 



ter of the head through which the stay-bolt passed 

 had been enlarged with a drift-pin, causing the iron 

 in the head to crack in three places, beginning at the 

 edge of the hole and running out into the body of the 

 head. The defects were repaired, and on the follow- 

 ing day, March 8th, the test was resumed, with the 

 result as shown in the following table : 



At 130 pounds a leak in the back head of the boiler, 

 which had started around the stay-bolt, checked the 

 draught to such an extent as to render further efforts 

 to increase the pressure futile. 



March 9th the boiler was repaired and put in good 

 order. On the following day, March 10th, the experi- 

 ments were resumed with 201 inches of water in the 

 boiler, 5i inches above the fire-line. Steam was gen- 

 erated slowly, but, contrary to our advice, the press- 

 ure was run up to 200 pounds before the discharge- 

 valve had been attempted to raise, and when an at- 

 tempt was made to raise it, it was found that it had 

 become fast to the seat : the lever attached to it broke, 

 and practically ended the test. The steam, however, 

 ran up to 275 pounds, when it began falling slowly, 

 until the pressure reached a point of safety, when the 

 fire was drawn and the boiler allowed to cool off. 



March 20th, the experiments were resumed. This 

 time the boiler with Mr. Lawson's appliance was 

 used. A steam-gauge was attached to the boiler 

 above and one below the diaphragm. The boiler 

 con tamed 18 inches of water. -Steam was generated 

 slowly, and when the pressure had reached 50 pounds, 

 operating the discharge-valve began with the follow- 

 ing results : 



At 220 pounds a leak, which had previously started 

 around the stay-bolt in the forward head of the boiler, 

 became so bad that the test had to be discontinued 

 until the necessary repairs could be made. Upon ex- 

 amination it was discovered that the hole in the cen- 



When the pressure in the boiler reached 300 pounds 

 to the square inch, it was unanimously decided that 

 the boiler had been sufficiently tested, as we intended 

 to cut out the diaphragm and make the final test with 

 the same boiler. The discharge-valve was then 

 opened and the steam allowed to escape ; the fire was 

 drawn, and when the boiler had cooled off sufficiently 

 an examination was made. It was found that the 

 water had been reduced to 11 inches, or 4 inches be- 

 low the fire-line. The rivets, seams, and all the 

 other parts of the boiler were critically examined, 

 and no strain, rupture, or any other weakness, was 

 discovered. The diaphragm was then cut out, leav- 

 ing the flanges riveted to the sides of the shell and 

 across the heads, with about three inches of the plate of 

 which the diaphragm was constructed. The boiler 

 was then placed in position for the final test, with 22 

 inches of water, 7 inches above the fire-line. When 

 steam was raised, the discharge-valve was operated, 

 with the following results : 



