Hanging a Defective Boiler Plug 



as a Warning 



A MINIATURE gallows from which 

 hangs a defective fusible plug re- 

 sponsible for a boiler explosion 

 which occurred on board the steamship 

 Jefferson, near Norfolk, Va., on May ii, 

 1914, is one of the interesting curios on the 

 walls of the office 

 of Secretary Red- 

 f ield , of the 

 Department of 

 Commerce in 

 Washington. It is 

 a grim reminder of 

 a tragedy which 

 cost the lives of 

 eleven men. A 

 small placard 

 above it reads: 



"A Murderer! 

 Hung for killing 

 eleven men." 



Below it are the 

 words : 



"The fusible (?) 

 plug which failed 

 to fuse. From the 

 boiler of the S. S. 

 Jefferson. Boiler 

 exploded. Eleven 

 lives lost." 



The plug con- 

 sisted of a threaded 

 brass bushing 

 about an inch and 

 a half in diameter, 

 with hexagonal 

 head. Through the 

 center of the bush- 

 ing runs a plug of 

 fusible metal, 

 which, in this in- 



Impurities of the fusible filling of this 

 plug prevented its blowing out and re- 

 sulted in the loss of eleven lives. So, 

 the plug was hanged as a murderer, in 

 a government bureau 



higher than 2,900 degrees Fahrenheit. 

 Impurities in the fusible metal, which 

 were the cause of its failure to blow out, 

 are easily discernible. In subsequent 

 investigations made by the United 

 States Bureau of Standards ten hundred 

 and fifty fusible 

 plugs were exam- 

 ined. These were 

 from one hundred 

 and five different 

 makers, and about 

 one hundred of 

 them had been in 

 actual use for from 

 four to twelve 

 months. From a 

 study of these 

 plugs the Bureau 

 recommends that 

 the fusible metal 

 itself should pre- 

 ferably be pure tin, 

 because it has been 

 found to be far 

 more reliable and 

 durable. The 

 Bureau further 

 recommends that 

 the tin be as free 

 as possible from 

 zinc and lead. 



One of the many 

 types of deteriora- 

 tion of fusible plug 

 fillings observed by 

 the Bureau consists 

 in the formation of 

 a network of mi- 

 nute thread-like 

 cracks or corrosion- 



stance, was defective; it did not blow 

 out when the water in the boiler became 

 low, thereby causing a disastrous explo- 

 sion. When the plug was sawed open 

 lengthwise it was found that most of the 

 original filling had disappeared, only a 

 few traces of it remaining embedded in 

 a dirty, greenish-white mass of tin 

 oxide, which would not melt until 

 heated to a temperature somewhat 



regions, ramifying in all directions. The 

 Bureau found that these penetrated the 

 metal and then broadened out until the 

 filling was largely, or wholly, oxidized 

 and destroyed. The presence of small 

 quantities of zinc in the tin was the 

 main contributing cause of the network 

 type of corrosion. This was proved 

 conclusively by the investigation con- 

 ducted after the disaster. 



810 



