174 ConTINuOUS Process EVAPORATORS 
so as to prevent the blades from running over the dry heating sur- 
face, cutting the copper. Simultaneously with the starting of the 
agitator the steam is turned into the jacket and then the milk 
intake valve is opened. 
The steam pressure on the jacket is kept uniform, preferably 
at 40 to 50 lbs. of steam. This machine evaporates the milk at 
atmospheric pressure. ‘The temperature of the milk in the con- 
centrator therefore, is practically the same as that of boiling 
water—212 degrees F.—at the sea level and varies only with the 
altitude of the location. The ratio of concentration is regulated 
by the rate of the milk inflow. As the milk inflow is increased. 
the ratio of concentration 1s reduced, because the amount of 
evaporation being constant, a smaller proportion of the water is 
taken out of the milk. 
The density is determined by the use of the Beaumé hydro- 
meter. If the density is greater than desired, more milk is 
allowed to flow into the machine. If the density is lower than 
desired the inflow of milk is reduced. 
Cooling of Condensed Milk.—From the discharge spout the 
condensed milk is run over a continuous cooler from which it 
escapes ready for packing in whatever form it is intended for. 
The disc continuous cooler has proven very suitable for this 
purpose. 
No subsequent superheating of the concentrated milk is 
necessary. This product can be made of any consistency desired, 
regardless of concentration, according to the thickness of the 
film that is allowed to form in the concentrator, and this in turn 
depends on the distance of the discharge from the periphery of 
the machine. 
THE RUFF CONDENSING EVAPORATOR. 
Principle of Machine and Process.—In the “Ruff Condensing 
Evaporator,” similar as in the “Continuous Concentrator,”’ the 
condensing is accomplished by the film principle, but in the Ruff 
machine the heating surface consists of one or more steam-heated, 
revolving drums, and atmospheric air is blown through the milk. 
This machine is applicable both, for continuous evaporation 
and for condensing in batches, 
