SEA-GOING HYDRAULIC DREDGES 115 



large compound condensing duplex pump made by the Stilwell- 

 Bierce & Smith- Vaile Co., of Dayton, O., for the water jets on the 

 section drag and in the discharge valves of the hoppers. This pump 

 has 18X30 in. steam and 24x24 in. water cylinders. Another duplex 

 pump, with 6x18 in. plungers, capable of pumping against a pressure 

 of 1000 Ibs. per sq.in., is employed for operating the hydraulic 

 cylinders by which the discharge valves in the hoppers are actuated 

 and also for operating the hoists for raising the suction pipe. 



The hoppers 'have rectangular bodies terminating in frustums 

 of rectangular inverted pyramids at the bottoms. The discharge 

 outlet in the bottom of each hopper is 4 ft. in diameter, and is closed 

 by a trunk valve of the same diameter which extends up through 

 the hopper and is raised and lowered by a 12-in. hydraulic cylinder. 

 In operation this trunk valve is raised about 3 ft. to allow the contents 

 of the hopper to discharge. To facilitate the discharge of these 

 contents and to loosen them up so that the trunk valve may be 

 easily hoisted, water is forced through the jets in the discharge 

 valve by the pump previously mentioned. When the discharge 

 is completed the centrifugal pump is started, forcing clear water 

 through the discharge pipes and into perforated flushing pipes 

 located in each hopper around the walls at a point where the vertical 

 and inclined sides join. This operation cleanses the discharge 

 pipes and the hoppers of all the undislodged contents. 



The main boiler and engine-room contains two boilers 14 ft. 

 in diameter and 11 ft. 10 in. long, operating under 180 Ibs. steam 

 pressure, and between the main boilers there is also a 7JX9 ft. donkey 

 boiler. Aft of the boilers are located two inverted-cylinder, direct- 

 acting, triple-expansion engines, with 18-, 25- and 48-in. cylinders, 

 with 30-in. stroke. The high-pressure and intermediate cylinders 

 have piston valves, and the low pressure cylinder has slide valves. 

 These engines drive twin screws. 



The operation of the dredge is as follows: The suction tube is 

 lowered to the bottom and the air exhausted from the centrifugal 

 pump by a 4-in. injector. When the pump is charged the pumping 

 engines are started, filling the tanks with water. The suction pipe 

 having fed itself into the bottom to a sufficient depth, the dredge 

 is moved ahead at a speed of about 25 or 30 ft. per minute, until 

 the hoppers are filled with dredgings. To loosen the material so 

 that the suction can secure it, the water jets previously noted are 

 kept in operation. When the hoppers are filled the suction pipe is 



