Milling cutterhead
Increasing the limit of rock strength that can be dredged by CSD's has always been done by increasing the cutting power on the cutting head. This is logical as more cutting power comes with a bigger ship with more pulling and pushing force and a higher ladder weight. This increases the normal and cutting forces that can be transferred to the rock.
Increasing cutting power will therefore increase the rock strength that can be dredged. But is this the only way? When looking at the performance of roadheaders, we can see that machines with cutting power as low as 300 kW are able to cut rock of 100-150 MPa UCS whereas a CSD capable of handling such rockstrength will have a cutting power of more than 4000 kW. On top of this, roadheaders work in dry conditions which is worse.
The reason is that roadheaders use a different cutting mechanism: milling instead of ripping.
This consideration was used to start the development of a cutting head to cut hard rock with low cutting power.
Design
Fitting point attack picks on a cutting head might seem easy but there are many variables that will determine the succes of a milling head:
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design of the cutting body
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position and number of point attack picks
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design of point attack picks
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dredging methodology
dredging