THE EXTRACTION OF THE JUICE BY MILLS 



217 



and hence, except when running at the maximum capacity, some power 

 is lost here. As opposed to this source of loss, the steam consumption per 

 horse-power is in a Corliss engine sensibly constant over a wide variation 

 in the power developed. However, if the house is able to take up all the 

 exhaust steam produced, there need be no heat loss here except that repre- 

 sented by " cylinder condensation," a source of loss which is probably a 

 little less (as a percentage of the steam used) in the turbine than in the 

 reciprocating engine. 



There are, however, a number of advantages connected with electric 

 drive, which may be briefly summarized : 



FIG. 123 



1. Absence of all oil in the exhaust. 



2. Compactness of plant and decreased cost of foundations. 



3. More extended control by means of recording watt-meters, this being 

 possible only with electric drive. 



In certain plants individual motor drive has been installed for each 

 unit of a train of mills. The executive can detect at once any variation 

 from the proper amount of power taken by any unit of a train, and by means 

 of the recording instruments can reconstruct the operation of the plant 

 over any period. It is this opportunity for a complete control that appeals 

 to the writer as the great advantage of the electric reduction gear. 



FIG. 124 



Milling Trains. Originally, and up to comparatively recent years, 

 only one mill was employed, and the introduction of a second unit (double 

 crushing) without the intermediate addition of water did not in any way 

 alter the principle of the process, which remained one of dry crushing. 



In a sense, Robinson's multiple roller mills (see below) form a train, 

 and the first instance of a single engine double-crushing plant is probably 

 that erected by Don Wenceslao Urrutia in Cuba in J.843, 11 and condemned 

 because it spoilt both juice and bagasse. At about the same time a three- 

 roller mill, followed by a two-roller with the addition of water, was in use 

 in Province Wellesley, and is illustrated by Wray in the " Practical Sugar 

 Planter" (1848). 



