Posted on November 16, 2022
INTRODUCTION
During your career in the aggregate industry you’ve likely encountered professionals that have offered
their opinion, with absolute certainty, as to how much your dredge should produce, even though they’ve
examined very little, if any, of your dredging operation.
The fact is, excavating material from the earth and transporting material through a pipeline is not an
opinion, but a science, and sizing up your dredge’s level of performance in this process will take data
and the application of some engineering.
THE BASICS
In order to best understand dredge performance, let’s briefly examine how a hydraulic dredge works. A hydraulic dredge is made up of two completely separate and independent systems working together in harmony; a material excavation system, and a material transport system.
Most professionals that offer dredge productivity estimates to aggregate producers tend to only look at the transport system and ignore the excavation system altogether. This leads to confusion and frustration and can cause the aggregate producer to purchase a dredge with an undersized excavation system.
The Excavation System
With respect to a typical basket style dredge cutter head, some of the facets of the design that affect its
production rate are:
- Horse Power
- Cutter Diameter
- Number of Cutter Blades
- RPM
Of the parameters shown above RPM affects the overall performance of the excavator due to its direct relationship to the breakout force produced by the excavator. Lowering the RPM increases the break out force of the cutter, while raising the RPM decreases the break out force.
For this reason, dredge designers strike a balance between these two values by selecting an RPM that is just fast enough to result in a production rate that matches, or slightly exceeds the transport capability of the dredge pump, while at the same time, leaving a sufficient amount of breakout force for the material.
