GROUND-WOOD PULP. i 
Upon leaving the grinder a large supply of water 1s added to the 
pulp, and the mixture is then screened. If it is to be shipped over a 
long distance, the pulp is run into laps by means either of wet 
machines or of hydraulic presses. Occasionally the pulp is dried on 
steam driers and run into rolls. When pulp is used where it is pro- 
duced, except for the need of storing to provide a supply in times of 
low water, it is thickened by means of feltless wet machines or deckers 
and immediately manufactured into paper. 
In the last few years a magazine pulp grinder has come into use, 
equipped with two pockets which are filled automatically from the 
magazine. The machine, however, has not been operated in this 
country to an extent which would enable a judgment to be formed 
regarding its efficiency and economy. 
Part IL—THE GRINDING OF COOKED AND UNCOOKED 
SPRUCE. 
EQUIPMENT USED IN THE EXPERIMENTS.‘ 
APPARATUS FOR COOKING. 
Cooking treatments prior to grinding were carried on in a cylin- 
drical closed steamer 3 feet in diameter by 8 feet high, designed for 
75 pounds’ working pressure. The ‘‘steamer” was fitted with steam, 
water, and vacuum connections and the necessary gauges and ther- 
mometers for determinations of pressure and temperature: An open 
steamer 6 feet wide, 8 feet long, and 3 feet deep was also available 
for cooking treatment at atmospheric pressuro. 
ELECTRICAL EQUIPMENT. 
In order to satisfactorily vary the conditions of grinding, secure 
adequate data on power consumption, and maintain the speed con- 
stant, it was necessary to install a rather complex system of electrical 
drive and control for the grinder. The method of speed regulation 
was known as the Ward Leonard system, and by its means a very 
flexible arrangement was secured. 
The installation consisted of a motor generator set of 460-kilo- 
volt-amperes full-load capacity and a direct-current, variable-speed 
motor having a full-load capacity of 500 horsepower at 300 revolu- — 
tions per minute. With the overload capacity it was possible to 
secure fully 75 per cent more power than the rating from each of the 
machines. 
Three-phase 60-cycle electric power was applied to the synchronous 
motor of the motor generator set at 2,300 volts. The generator of the 
motor generator set was separately excited and by means of a rheostat 
1A more detailed description of the equipment of the Forest Service laboratory at Wausau, Wis., is 
given in an unnumbered publication of the Forest Service, “Experiments with Jack Pine and Hemlock 
for Mechanical Pulp.” ; 
