CANE SUGAR. 



the writer has noticed that the capacity of mills otherwise similar is 

 proportional to the cubic contents of one roller, and that, in the case of a 

 nine-roller mill and crusher, the following simple relation holds. The capacity 

 in short tons of cane per hour is equal to the cubic contents in feet of one roller. 



Three sizes of rollers often found are 30 in. X 60 in., 32 in. x 66 in., 

 34 in. X 78 in. ; the cubic contents of these rollers are 24*5 c. ft., 30*7 c. ft., 

 and 41*4 c. ft., and these figures represent very closely the amount of cane 

 treated by mills of this size in combination with a cane preparer. 



The addition of a fourth mill is found in practice to add at least 25 per 

 cent, to the capacity without detriment to the quality of the work, and the 

 absence of a cane preparer to take away about 10 per cent. 



FIG. 128. 



The capacity of an existing plant can be varied within certain limits 

 without detriment to the quality of the work by regulation of the escribed 

 volume; this can be controlled by increasing the peripheral speed of the rollers 

 or by increasing the opening between them ; if the capacity of a mill is to be 

 increased on these lines, it is of course necessary that there be sufficient 

 engine power available to treat the increased quantity of cane. The capacity 

 of a mill is also affected by otber causes that cannot well be treated on paper ; 

 some of these are : 



1 . The nature of the material treated, including such points as the hard- 

 ness, brittleness, and fibre content of the canes. 



2. The ' slip ' of the mill. 



3. The roughness of the rollers ; it is a matter of experience that the 

 capacity of a mill is increased with rough surfaces, and rollers are now made 

 with a special coarse-grained surface ; grooving the rollers has a similar 

 effect. Forms of grooves as found in practice are shown in Fig. 128. 



5. The setting of the trash bar. 



6. The regularity and evenness of the feed. 



Surface Speed of Rollers as affecting Expression of 

 Juice. A number of years ago 15 to 16 feet per minute was a usual surface 



200 



