TRANSFORMERS 



431 



For water-cooled transformers the tanks are mostly of a heavy 

 steel-plate construction with all joints welded (Fig. 272). Some- 

 times a corrugated design is also used to increase the radiating 

 surface. 



It is advisable to have the transformer covers tight-fitting to 



FIG. 270. Combination Self-cooled, Water-cooled Transformer. 



prevent entrance of moisture. This is effectively accomplished 

 by placing a gasket between the tank and the cover. In order, 

 however, to maintain atmospheric pressure in the air space above 

 the oil, " breathers " are, as a rule, used. This equalizes the 

 pressure within and without the tank and prevents the precipi- 



