310 ‘THe Spray Process 
Most of these chambers are rectangular, measure from about 
12 feet in length, width and height upward to much larger dimen- 
sions. Some are longer than they are wide and others are much 
higher than they are wide and long. Still others are of the circu- 
lar type, resembling small silos, and some are cone-shape. 
The desiccating chambers are usually completely lined with 
tin plate on the inside, making them air tight or nearly so. In 
order to prevent waste of heat by radiation through the walls, top 
and bottom, they must be properly insulated. This is generally 
done with asbestos sheeting. 
Spray Nozzles.—The milk enters the desiccating chamber 
through one or more spray nozzles, under a pressure of about 
3,000 pounds. ‘The spray nozzles are generally located in the side 
of the drying chamber in close proximity to the top, so as to give 
the spray particles as far a distance to fall through the heated air 
as the height of the chamber permits. Or the spray nozzle may be 
located in or near the eenter of the drying chamber, in its upper 
portion, in which case the spray issues outward radially, or is blown 
out of the nozzle tangentially by giving the spray nozzle a rotary 
motion. 
When more than one spray nozzle is used, the multiple noz- 
zles are either arranged in a straight row along one side, or they 
may be distributed over two or over all four sides of the desic- 
cating chamber. 
Different types of spray nozzles or atomizers are used. In 
some hot air under pressure, or steam, propels and blows the milk 
through the nozzle on a similar principle as the boiler water in- 
jector. In other cases the spray nozzle consists of a heavy black 
iron cap, about one and one-quarter inch long and with a one-half 
inch threaded bore. ‘This cap is screwed on to the end of the 
milk pipe, or its laterals. In the center of the closed end, the cap 
has a very fine opening with a diameter of from one-half to one 
millimeter (.02 to .04 inch). A small brass disc, about one-quar- 
ter inch thick and snugly fitting into the iron cap, lays against 
the closed end of the cap and covers the small orifice. This brass 
disc carries two minute spiral grooves at its periphery, through 
which the milk under pressure is forced between disc and cap 
