is assured. Where it is possible to make only one inlet and one outlet connection 

 to the superheater, it has ordinarily been found advisable to use a construction 

 employing cores within the superheater tubes. It may be readily understood that 

 if the total cross sectional area of the tubes is so great in proportion to that of 

 the manifolds as to cause a marked decrease in the velocity of the steam through the 

 tubes, there will be a tendency on the part of the steam to take the shortest course 

 between the point of introduction and the outlet manifold. By the use of cores 

 the ratio of the area through the tubes to that of the manifold may be made 

 such as to assure all tubes carrying their proper proportion of steam under any 

 conditions of operation. 



The installation of cores in superheater tubes will cause a drop in pressure 

 through the superheater due to the added friction resistance to the steam. This 

 drop in pressure can be calculated for any set of conditions and when such a drop 

 is kept within reasonable limits with the boiler operating at, say, 200 per cent of 

 its rated capacity, it may be taken as an assurance that all tubes of the superheater 

 are carrying their proportion of the steam. If the cores are not properly designed, 

 their use may cause a drop in pressure through the superheater that is objectionable. 



The method of installing cores and holding them in position in superheaters 

 of this description will be described in detail later. 



The cored type of superheater as manufactured by The Babcock & Wilcox 

 Co. has given eminently satisfactory results in boilers where its use has been 

 believed advisable. 



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