ABSTRACT

This paper describes the design of hydraulic system of a cutter head pipeline dredger. Hydraulic dredging uses centrifugal pumps to transport dredged material a long a pipeline. A cutter head for a cutter suction dredger to be mounted rotatably about a cutter head center axis with respect to a suction device for sucking up material cut loose by the cutter head from the bottom of a body of water, which cutter head includes a base ring, a boss spaced from the base ring in the direction of the center axis, and a number of arms which extend from the base ring to the boss and are distributed at regular intervals in the peripheral direction, each arm has a series of teeth located on the radially outermost parts of the arm and directed outwards at an angle with respect to the peripheral direction, the direction of rotation of the cutter head being set such that the teeth perform a cutting movement, with non-return mechanisms, preventing movement of cut material from the center axis to the exterior.

Key words: Dredging, pipeline, cutter suction dredge, hydraulic system, ladder pump.

TABLE OF CONTENTS

 TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• PROBLEM STATEMENT
• AIM/OBJECTIVE OF THE PROJECT
• SCOPE OF THE PROJECT
• APPLICATION OF DREDGE CUTTER HEAD
• ADVANTAGES of CUTTER HEAD DREDGERS
• LIMITATIONS of CUTTER HEAD DREDGERS

CHAPTER TWO

LITERATURE REVIEW

2.1     REVIEW OF RELATED STUDIES

2.2     TYPES OF HYDRAULIC DREDGERS

2.3     MAJOR DREDGING EQUIPMENT AND OPERATIONS

2.4      RESEARCH GAPS AND FUTURE RESEARCH

CHAPTER THREE

3.0      METHODOLOGY

3.1      DESIGN MODEL

3.2      SYSTEM DESIGN

CHAPTER FOUR

4.1     RESULTS AND DISCUSSIONS

CHAPTER FIVE

• CONCLUSIONS

REFERENCES

CHAPTER ONE

1.0                                                              INTRODUCTION

1.1                                                BACKGROUND OF THE STUDY

The development of the dredging industry, the increase in population, and larger draft vessels contribute to a rise in the demand of dredging for various purposes. Dredges build and maintain artificial islands, harbors, and channels (MacLeod and Butler 2019). Dredging increases the water depth of ship entrance channels in order to prevent a vessel from encountering the channel bottom. A dredge is also used for mining to obtain essential industrial materials such as gold, tin, rutile, etc. (Hennart 2016).

The cutter head dredge is one type of hydraulic dredge that is widely used in dredging navigable waterways (Randall et al. 2018). Because the cutter head dredge can perform both excavation and transportation, its efficiency is higher than other types of dredges (Tang et al. 2019). The cutter head dredge uses a rotating cutter in front of the suction inlet to excavate bottom materials. The excavated material enters the pipe inlet on the suction side of a centrifugal pump and is transported to a barge or a placement site through a pipeline (Paulin et al. 2013). The maximum operating water depth for the cutter suction dredge without a ladder pump or submerged pump is approximately 30-35 m (Jukes et al. 2011; Pauline et al. 2014), but deeper operating depths are possible by adding a ladder pump.

It is important to estimate production of the dredged material (Miedema 2018). For the cutter suction dredge, production is a function of the operating flow rate, the solids concentration by volume, and the dredging efficiency. In addition, the operating flow rate is highly related to the critical flow rate, the net positive suction head (NPSH), and pump characteristics. Turner (2016) estimates production for hydraulic dredges based on these parameters. In order to prevent pump cavitation and overcome the power limitation of any individual pump, the main pump, ladder pump, and booster pumps must be located properly.

Dredge cutterheads are generally hemispherical with a multiplicity of hard rock cutting teeth or replaceable edges projecting outwardly from helical support arms or blades disposed about the hemispherical surface of the cutterhead. The cutterhead has a hub which fits around a shaft that provides the torque for turning the cutterhead in its operation of dredging. The cutterhead encounters all kinds of materials, including rock, sand and clay which must be removed from the bed being dredged.

The design of hydraulic system of a cutter head pipeline dredger is described in this work.

1.2                                                       PROBLEM STATEMENT

Conventional cutterhead arms are shaped to minimize wear, but are not designed to move material. However, one of the problems encountered by cutterheads is that the material loosened by the cutting teeth must be directed into a suction pipe in order to be removed from the bottom of the waterway. As the cutterhead moves across the waterway bottom, the cutting teeth dig below the bed to loosen material. Unfortunately, a substantial portion of the material loosened by the cutting teeth does not reach the suction mouth, which is generally located adjacent to the lower side of the ring of the cutterhead. The hydraulic system of this machine make it possible for the machine to overcome these challenges/limitations

1.3                                         AIM AND OBJECTIVES OF THE STUDY

The main aim of this work is to design a hydraulic system of a cutter head pipeline dredger. The objectives are:

1. To build a cutter suction dredger provided with a suction device having a cutter head.
2. To produce a sucking action in the suction device in order to create a flow of water and cut ground material from the interior of the suction head and via the openings between the arms of the suction head,

1.4                                                        SCOPE OF THE STUDY

The scope of this work covers designing a cutter head for a cutter suction dredger which intended to be mounted rotatably about a cutter head center axis with respect to a suction device for sucking up material which has been cut loose by the cutter head from the bottom of a body of water, which cutter head comprises a base ring, a core located at a distance from the base ring in the direction of the center axis, as well as a plurality of arms which extend from the base ring to the core, each of which arms has a series of teeth located on the radially outermost parts of the arm and directed outwards at an angle with respect to the peripheral direction, the direction of rotation of the cutter head being set in such a manner that the teeth perform a cutting movement.

A cutter head of this type is known, and is used in those circumstances in which material can be cut from the bottom of a body of water. For this purpose, the cutter head is provided with cutting teeth, which are attached to the cutter head by means of a replaceable holder system. Depending on the ground material which is being processed, the teeth are subject to considerable wear. After some time, the teeth are consequently no longer suitable for cutting ground material, so that they have to be replaced.

1.5                                      APPLICATION OF DREDGE CUTTER HEAD

Dredge cutter head used to remove material from harbors, shipping channels, and other marine environments and mining operations. They are also used for larger dredging projects such as navigation channels and port development and maintenance and land reclamation and in major projects

1.6                  ADVANTAGES of CUTTER HEAD DREDGERS

The most powerful cutters can dredge hard rock effectively on a continuous basis. The self-propelled CSDs can travel long distances and be deployed in remote locations, far from their home port, making them flexible to be used all over the world. They can work in shallow waters and they also have flexible discharge alternatives.

Small and medium size cutter head dredgers can be dismountable and transportable over land. The hull is then comprised of a series of pontoons, with the one pontoon containing the machinery.

1.8                                    LIMITATIONS of CUTTER HEAD DREDGERS

Cutter suction dredges are sensitive to rough seas and are not easily moved whilst working.