122 



USRL TEST STATIONS 



Figure 59. View of high-pressure tank, showing top working area. 



riage lengthwise of the tank and the other rotates it 

 about a vertical axis through a maximum of 30 de- 

 grees. The travel of the carriage allows the distance 

 between two transducers to be varied from 4 to 8 feet. 



Each port cover is held securely in place by four 

 hydraulically operated wedges, constrained in the 

 vertical direction by bridges. Each wedge, cut at an 

 angle of 10 degrees, exerts a downward force of 

 60,000 pounds on the cover when actuated by a 

 hydraulic cylinder operated at a fluid pressure of 

 1,000 pounds per square inch. The hydraulic system 

 for operating the wedges is shown in Figure 60. The 

 hydraulic system pump is equipped with a 1,000 

 pounds per square inch automatic by-pass and can 

 deliver 3 gallons per minute at this pressure. 



The tank is filled directly from the lake and, since 

 it is drained frequently, no provision is made for in- 

 hibiting the growth of organisms except that several 

 chemical briquettes like those used in the high-fre- 

 quency system are left in the tank to dissolve. The 



system for filling and applying pressure is shown in 

 Figure 61. A pump with a capacity of 1,500 gallons 

 per hour is used for filling the tank and, when neces- 

 sary, for circulating the water through a heat ex- 

 changer coupled to the heating system of the labora- 

 tory. With all valves closed, the pressure is applied by 

 a high-pressure pump governed by an adjustable pres- 

 sure switch. The control is automatic and will keep 

 the pressure at any value up to 300 lb per sq in. within 

 ± 5. Two safety valves protect the system from exces- 

 sive hydrostatic pressures. 



The interior of the tank has been coated with the 

 bubble layer developed by the Massachusetts Insti- 

 tute of Technology in order to obtain some sound ab- 

 sorption at the walls. 



Acoustic Measurements in High-Pressure 

 Tank 



Acoustic measurements in the tank differ from 

 those in a free field because of the relatively small size 



