150 THE DESIGN OF STATIC TRANSFORMERS 



lower portion of the sides into a mould, into which molten iron 

 is poured, and which forms the base. The method has the 

 defect that blow-holes may occur around the joint, which, 

 though not sufficiently pronounced to be detected at the time, 

 may, under the continual influence of the hot oil, ultimately 



FIG. 86. Method of jointing the sides and bottom of :i t runsformer case. 



develop into leaks. Ordinary materials, such as are used in 

 everyday workshop practice to fill in flaws in cast-iron, are 

 useless for the purpose of oil tanks, since the ingredients of 

 which they are composed are often readily dissolved by hot 

 oil. 



The mechanical construction of a sheet-iron case requires 

 careful attention, since the thickness of the walls is too slight 

 to permit that the weight of the transformer shall be taken up 

 by the sheet iron itself. On the contrary, the weight should 



