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324 "The safety valve off the port boil- er was then rigged up and pressure applied. This valve lifted and let go at exactly 150 pounds pressure, the steam pressure that the boilers were allowed. "The fact that the safety valve off the wrecked boiler let go light, was due, we think, to its having landed heavily on its spindle, thereby spring- ing the valve seat and easing the tension on the spring. The results of testing these valves compels us to be- lieve that excess pressure did not cause the explosion. The Cause of the Explosion "We now come to that part of the boiler which leads us to believe was the direct cause of the explosion, and that is a defective part in the rear head of the boiler. In examining the wrecked boiler we noted that a piece of the flange of the rear head was still fast to the shell. This piece was di- rectly on the bottom, and was 64 in. long, with irregular ends. Examina- tion of this piece of flange showed that it was greatly deteriorated along the edge where it had been torn off the head. This deterioration existed just in the turn of the heel of the flange on the inside of the boiler, and was due to pitting and grooving. The head plate was 3% in. thick, and where this defect existed some of the grooves "or cracks extended down into the metal to a depth, in some places, of % in. leaving only % in. of good material. This groove did not ex- tend in one straight groove but ran the entire distance of 64 in. in three general grooves, with an average depth of 3 in. In some places the grooves were not so deep and in others they were deeper, and when it let go, the head gave way in the middle crown. After examining the piece of flange left on the head we then examined the lower half of the rear head which we found lying aboard the boat. There was a part of the flange missing on this head that corresponded identi- cally with the piece that was left at- tached to the shell. The same con- dition as to pitting and grooving pre- vailed on this part of the head as it did on the piece attached to the shell. "In examining the lower half of the head, we noted that all of the rivets that fastened it to the shell plates were sheared off, except those in the defective piece above mentioned. The rivets that fastened this part of the head to the shell were all in place, intact, and in good order. From 'this we deduce that this weakened part had reached its limit and burst, and in bursting it gained such momentum THE MARINE REVIEW that it ripped out the whole back head, thus releasing the entire boiler pressure through this large opening, and creating this sad and terrible dis- aster. "Our theory in this respect is borne out by the fact that all the interior parts of the boiler show that some terrific force drove them all aft, while the opposing force was expend- ed in driving the boiler forward and out of the ship. "In view of the above facts and the absence of any evidence of neg- ligence on the part of the engineers, together with their previous good rec- ord and character, we herewith en- tirely exonerate them from any blame « or responsibility for the accident. "In rendering this decision, we do. so because we are of the belief that the engineers did not know of the defect which existed. One reason for this belief is that the defect existed in such a place that owing to the in- The front end showed the top part of the head caved inwardly about 12° in., leaving the tube ends projecting fom 1 to 3 in., in all manner' of shapes, some flattened, some bent and some twisted. The furnace fronts were off, grates out, and man and hand hole plates missing. "Examination of the shell showed it to be intact, save indentations and Hidises received in its fight.. The shell was entirely stripped of all fit- tings, valves, etc. Upon careful and minute examination we could not dis- cover any signs of rupture or undue strain in the shell plates or longitud- inal seams. The longitudinal seams are double butt strapped, and triple riveted, with 11/16-in. rivets, pitch 3% in. apart. Entire Rear Head Blown Out "Next we went to the back end of the boiler and here we found prac- tically the entire rear head blown out. This head was originally put in con- vexly, the flange being entered into shell and fastened to the shell with a double row of 11/16-in. -- rivets, pitched 3% in. apart, and staggered, Rows of rivets 2 in. apart. The head was put in in two pieces, with a dou- ble riveted seam across the center line of the head. (Rivets 11/16 in, and 3%-in. pitch.) The lower half of this was blown entirely away, and later found lying just back of the boiler's original position aboard the ship. The top half of the rear head was torn off about one-half the distance from center line of boiler to the top of the shell, and doubled back outwardly as one would turn a leaf in a book. The stay bolts that braced this rear 'in our possession. September, 1913 head and the back sheets of the com- bustion chamber, pulled out of the combustion chamber sheets and re- mained in the head sheets. An ex- amination of these stay bolts showed that they were 1%-in. bolts, out- side diameter, and pitched 5 in. by 5Y in. apart. Some of the stay bolts that had -been renewed at some time showed 1% in. outside diameter. A earetul éxamination of these | stay bolts failed to disclose that any of them had been broken previous to the explosion: All the rivets 'that fast- ened the head to the shell plates were sheared off, save for a few that still hold a piece of the head flange to the shell, around the bottom, and which will be taken up later in this report. Blown to Pieces "The boiler originally had two sep- arate combustion chambers and two Adamson furnaces. Not an atom or single vestige of either combustion chamber remained in the boiler. Both combustion chambers were torn off from the furnace ends, leaving noth- ing where they had been, but the torn ends of the furnaces and broken, bent and twisted tube ends. "The through braces over the top row of tubes were practically intact, save that they were all loosened up and pushed bodily backward. The staybolts from the side of the com- bustion chamber to the shells, were pulled out of the combustion chamber sheets and remained in the shell sheets. "Upon returning to the steamer we first went into the combustion cham- ber of the port boiler, the one left in the ship. We examined this boiler for indications of low water, but could not find any. Both of the fusible plugs in this boiler were found to be in ex- cellent condition. We removed both these fusible plugs and they are now At the time we examined this port boiler, it was about half full of water and there was no sign of leaks anywhere. The tubes and tube ends, tube sheets, rivets, stays, etc., were all in good or- der. We could not discover any of the unusual indications that there had been low water. "We next turned our attention to locating the fusible plugs that were in the exploded boiler, and looking for low water indications. Among the de- bris we located parts of a combustion chamber which we are inclined to think was the port combustion cham- ber of the exploded boiler. This piece of wreckage was twisted and bent almost beyond recognition. In_ this combustion chamber we found one iiss