CHAPTER IX 

 CLASSIFICATION AND CAPACITIES OF DREDGES 



THERE is such a large variety of dredging machines on the market 

 that it is not very easy to give a clear classification of them. Then, 

 too, when the details of the various machines are considered, things 

 look more discouraging; since machines that appear to be almost 

 equals, vary greatly in the construction of their different parts. 

 Such a wide difference is caused by the fact that dredges are usually 

 designed for working on a specified improvement, and are constructed 

 to satisfy all the requirements of the indicated work. As there are 

 not two jobs alike, the dredges are built with such a large variety 

 of details that it is difficult to find two dredges perfectly identical in 

 every respect. 



However, dredges can be divided into two classes, continuous 

 and intermittent; the former removing continuously the material 

 from the bottom of the body of water, while the latter engage the 

 bottom at intervals. Continuous dredges are of four different 

 types: the ladder, the hydraulic, the stirring and the pneumatic; 

 while the intermittent are divided into only two classes, the dipper 

 and the grapple dredges. 



Each one of these different types of dredges can be subdivided 

 again into various groups. All preserving, however, the principal 

 characteristics of their type. 



The ladder dredge may be mounted on a hull constructed not 

 only for carrying all the various machines and housing the crew, 

 but containing also large bunkers where the excavated materials arc 

 stored, while being transported to the dumping place. This type is 

 called the sea-going ladder hopper dredge. On the other hand the 

 hulk may be built so as to carry everything connected with the ser- 

 vice of the dredge, while the excavated materials are dumped into 

 scows, and thus we have the simple ladder dredge. It may be either 

 self-propelling or stationary, depending upon the machines that 

 are mounted on board the vesse permitting the dredge to go 



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