SEPARATION OF CREAM. 148 
matic governor on it, the speed is usually quite uniform. Where 
steam-turbine machines are used, the speed of the machine is 
more likely to vary with the different amounts of steam pressure 
on the boiler. With turbine separators it is very essential to 
keep an even steam pressure. Some turbine separators have 
a safety-valve attached to prevent too high speed. 
The reason why the prevention of a variation in speed is so 
essential is that a slight variation in the speed has a compara- 
tively large effect upon reducing or increasing the centrifugal 
force. The centrifugal force generated in a machine varies 
according to the diameter of the bowl, and according to the 
speed of the machine. The greater the diameter of the bowl, 
the less speed of velocity is required in order to get a certain 
force. The centrifugal force varies in direct proportion to the 
diameter of the bowl; that is, if the diameter of the bowl be 
doubled, then at the same speed, the centrifugal force has been 
doubled. The centrifugal force varies in quadratic proportion 
to the speed of the machine; that is, if the speed of the sepa- 
rator is doubled, the centrifugal force is increased four times. 
From this it will be seen that speed is a great factor in deter- 
mining the centrifugal force generated. It is not a good plan 
to have the diameter of the bowl too large, for the following 
reasons: A large bowl is more likely to be thrown out of balance; 
it is harder to keep on the bearings; and it is heavier and more 
unhandy to handle. For these reasons it is better to lessen the 
diameter of the bow! and increase the speed. This, of course, 
is true only to a certain limit. 
Steadiness in Running.—Smooth running of a separator is 
one of the first essentials. If a machine runs roughly, there 
will not be good separation, and it is dangerous to runit. The 
bowl itself is likely to jump out, or burst. The causes for 
unsteadiness in running are many. It may be due to a bent 
or sprung spindle; the machine not standing level; changing 
covers to bowls; using clamps which do not fit the bowl cover; 
unclean, worn-out bearings; condition of the bowl, and con- 
trivances inside the bowl; and dented and rusty bowls. Occa- 
