The table shows that the saving in steam consumption with 105 degrees 

 of superheat was 15.3 per cent and in heat consumption about 10 per cent. 

 This may be safely stated to be a conservative representation of the saving that 

 may be accomplished by the use of superheated steam in a plant as a whole, 



TABLE 2 

 RESULTS OF " IDALIA" TESTS 



where superheated steam is furnished not only to the main engine but also to the 

 auxiliaries. The figures may be taken as conservative for the reason that in 

 addition to the saving as shown in the table, there would be in an ordinary plant 

 a saving much greater than is generally realized in the drips, where the loss with 

 saturated steam is greatly in excess of that with superheated steam. 



That there is a saving possible through the use of superheated steam is 

 clearly demonstrated by the foregoing discussion. A consideration of certain 

 of the factors upon which the question of superheater installation is based 

 follows, together with a discussion of certain objections that have been raised 

 against such an apparatus. 



SUPERHEATER DESIGN Though a properly designed superheater will tend 

 to raise rather than decrease the efficiency of the boiler in which it is installed, it 

 does not follow that all superheaters are efficient. There are a number of 

 features to be observed in the design of integral superheaters. 



If the gases in passing over the superheater do not follow the path they 

 would ordinarily take in passing over the boiler heating surface, a loss may result. 

 This is particularly true when a portion of the gases are passed directly to the 

 superheater and are made to pass over only a portion of the boiler heating surface. 

 While a location in the direct path of the gases is essential for superheater 

 efficiency, from the standpoint of the boiler's operation this location and the 

 arrangement of the superheating surface must be such as to cause no undue 

 frictional resistance to the gases in their passage. 



41 



