10 BULLETIN 904, U. S. DEPARTMENT OF AGRICULTURE. 



on germs from the dry process and below S per cent when using 

 material from the wet process. 



A peculiar series of explosions often takes place in these expellers, 

 mostly when used on germs obtained by the dry process. The cause 

 does not appear to be well understood, but it is the general opinion 

 that an excessive or an insufficient amount of either moisture or 

 fiber is responsible. 



The oil obtained, which in most cases is of a golden color, is next 

 passed through filter presses which remove the fine meal. This 



Fig. 9. — Complete 1-expeller oil plant. 



meal is then returned to the expellers and mixed with the fresh 

 material. 



Hydraulic presses are used only to a very limited extent, having 

 been almost entirely displaced by expellers. The question of the 

 relative expense of operating presses and expellers is interesting, and 

 several factors are involved. The cost of operating presses is some- 

 what increased at present (1920) owing to the expense of the press 

 cloths, which cost about $2 a yard. It is estimated that the entire 

 set of cloths must be replaced every 60 days, and since 45 yards are 

 required for one press of 15 plates, this item amounts to $90, or $1.50 



