312 Toe Spray Proctss 
and continuous flow through the spray nozzles and the deep stuf- 
fing boxes enhance the tightness of the seal. ‘lhe hardening of 
condensed milk on the plungers is prevented by an open pot water- 
seal which completely merges the stuffing boxes, the water serving 
to both cool and lubricate the packing and to prevent its being hard- 
ened by absorbing condensed milk. While the pump is in operation 
a small stream of cold water is allowed to run into this water pot 
and to overflow through a suitable opening. 
These pressure pumps should also be provided with proper 
relief or overflow valves, so as to avoid the danger of excessive 
pressure and variation in the spray, in case several of the spray 
nozzles should become clogged simultaneously. 
At the finish of the run of milk, a quantity of water should 
be pumped through these high pressure pumps and pipes and it 
is advisable to allow the pumps and pipes to stand full of water 
when they are not in use, so as to loosen and remove remnants of 
condensed milk, preventing their accumulation in the cylinders and 
avoiding difficulties incident to plugging and clogging. 
The pressure used at which the milk is forced through the 
spray nozzles varies from 800 to 3,500 pounds per square inch, 
the usual range of pressure employed fluctuates between 2,000 and 
3,000 pounds. ‘The multiple nozzles with the fine openings require 
less pressure to secure the same atomizing effect than when fewer 
or one large nozzle is used. 
Hot Air Intake and Discharge.—he heated air enters the 
drying chamber at points varying with different types of cham- 
bers. Where the spray issues forth from nozzles located all on 
one side, the heated air often 1s admitted through a slot located 
directly under the spray nozzles and the air travels in the same 
direction as the spray and mixes with it. 
In desiccating chambers in which the spray nozzles are in- 
stalled on all sides, the heated air may enter near the bottom in 
the center of the desiccating chamber, pass up through and mix- 
ing evenly with the spray that issues from all sides toward the 
center. Or the heated air may enter at the top and pass downward 
with the spray. Or it may enter at the periphery at various points 
near the top, in the form of a cyclonic current moving spirally to- 
ward the center, and escaping in the center through the top of the 
desiccating chamber. 
