CASTOR-OIL INDUSTRY. 21 



Expellers for castor beans should be designed similar to those 

 used for copra; other types are not as satisfactory. Such machines 

 have three worm flights on the pressing screw, whereas those intended 

 for crushing other more fibrous and lower oil-bearing materials have 

 only two flights. 



Castor beans being low in fiber can not readily be handled in the 

 expellers when excessive pressures are applied, owing to the large 

 quantity of meal which accompanies the oil. If subsidiary equip- 

 ment is used for removing the meal, this objection is minimized. 

 However, inasmuch as such high pressures are accompanied with 

 the generation of appreciable quantities of heat, which serve to darken 

 the oil, and also since the cake is to be extracted for the residual oil, 

 the market for which is only very slighly below that of pressed oil, 

 good practice applies comparatively little pressure, which results 

 in the production of a cake about seven-sixteenths of an inch thick 

 containing about the same amount of oil as that produced by cage 

 presses, namely, 12 to 15 per cent. 



Because of the necessity for some binder to hold the cake within 

 the machine and to preclude the squirting of the meal, it is impracti- 

 cable to decorticate castor beans. However, if decortication is 

 desired for any purpose, the necessary binder can be mixed with 

 the kernels to hold them and to form a cake. To test this method, 

 decorticated castor beans were mixed with 9 per cent of peanut hulls 

 and expelled as usual. The resultant cake came out in very good 

 form, and the oil was quite free from meal. Since decortication 

 reduced the tonnage pressed by 35 per cent and the added fiber was 

 only 9 per cent, it follows that a net reduction in tonnage of about 

 26 per cent was effected, resulting in approximately one-third greater 

 expelling capacity. 



The unsatisfactory results accompanying earlier attempts to apply 

 the expeller to castor-bean oil manufacture are not hard to under- 

 stand. The wearing parts of the expellers made 15 years ago were 

 of cast steel and consequently were quite susceptible to the abrasive 

 action of the hard siliceous seed coats. Since then, however, the 

 wearing parts are of case-hardened steel, which presents an altogether 

 different aspect to the abrasive action. The Government castor-oil 

 mill at Gainesville, Fla., has an installation of 15 expellers which 

 have been operating for several months and yet show actually less 

 wear than is observed when used for expelling peanuts. Out of a 

 possible linear movement of 2\ inches in which the cones can be 

 moved to take up the wear, they have been taken up only half an inch. 



A test batch of 1,701 pounds (37 bushels) of castor beans heated 

 to 140° F. was expelled in a regularly installed factory expeller. The 

 operation required 2.27 hours and yielded 727 pounds of oil and 920 

 pounds of cake. Based on the 46-pound bushel, this is equivalent to 



