Dredgers Ships: Types of Dredgers and Their Uses in Offshore Operations

Dredgers are an important part of the global shipping fleet, and different types of dredgers dig and scrape the seabed for various reasons. Without them, many coastal waterways and ports around the world would be unusable, which would significantly impact the entire global supply chain.

If you are interested in getting the lowdown on dredgers and their uses, keep reading as we will give you detailed information about these very important vessels on the next page.

What is a Dredgers and Its Uses?

Let’s first understand what bulldozers are exactly. Their definition is actually pretty simple: They are vessels that can remove and transport material, such as sediment and clay, from the bottom of a body of water. But like many aspects of the marine world, things get a bit more complicated when considering the types of dredgers—something we will explain to you later on this page.

But why are dredgers in such high demand? The answer lies in its various functions, most of which are vital to shipping and industry. Some of the most common jobs a dredger does include:

• Deepening waters to ensure that ships have enough depth.
• Creating new ports, which require a specific water depth to operate effectively.
• Extracting various materials from underwater.
• Removing any contaminants that may be on the bottom of a body of water
• Collecting sand for rebuilding beaches often erodes, so additional sand is needed.
• Collecting sand to turn it into concrete.

As you can see, dredgers are an important tool for the shipping industry. Many dredgers also require the support of tugboats and boats to transport workers from the ship to shore and vice versa.

Types of dredgers

Now, let’s take a look at the different types of dredgers available. All types of dredgers have advantages and disadvantages and meet different requirements.

Firstly, it’s worth noting that dredgers fall into one of three categories. Among them:

Fixed. These dredgers are built in situ and supported by pillars extending from the bottom.

Portable. These dredgers can be moved from one place to another, but they are not powered, so they need to be moved by other vessels, such as tugboats.

Self-propelled. These dredgers are also mobile and can use their own power to move.

All dredgers can also be divided into three other categories: mechanical, hydraulic/suction, and other. Learn more about mechanical and hydraulic/suction dredgers.

Mechanical Dredgers

Most types of dredgers are mechanical, but what does that mean? Well, they all use a bucket to accomplish whatever task may be in question. That is why they are often referred to as bucket dredgers.

Not only will you find the standard bucket attached to a mechanical dredger, but a variety of other attachments are also available, making them very versatile vessels. These include ladles, spoons, and ladders.

You will find fixed, portable, and self-propelled mechanical dredgers, but they must remain in one place and be secured using anchors or posts when the work is done. Mechanical dredgers need to be fixed because they can easily change position due to the pressure of the bucket on the bed. They can stay in the same position and work more efficiently by fixing them.

Mechanical dozers can be divided into different types. You can see some of the most commonly used types of mechanical dozers below.

Shovel dredgers

Shovel dredgers are among the most common types of dredgers worldwide. They are attached to a boat and work in a simple way, using a bucket to shovel material forward and away from the dozer—just like when you use a shovel in your backyard. The dredger uses a potato, which increases its power. Although not self-propelled, it can use the potato to move forward.

This type of dredger is particularly effective in tight spaces, and its power makes it the dozer of choice when it comes to clearing particularly tough material, such as clay, stone, and explosive rock. It can also be used to clear obstructions in waterways, such as abandoned buildings. On the downside, it can cause a lot of sediment disturbance and can only function at limited depths.

Backhoe Loader Excavator

Backhoe excavators are very similar to shovel excavators in that they also use a bucket to dig in an arc. They differ from backhoe excavators in that they shovel material towards the backhoe loader, just like a standard excavator would do on a construction site. The excavated material is placed on a barge and then transported to a specific site.

This type of bulldozer excavator is very popular and can be used in various situations and to dredge a variety of materials. Its most common use is for beach protection projects. More modern backhoe excavators can be used for dredging at depths of 30 meters or more. Most backhoe excavators are not self-propelled and, therefore, must be towed into place.

Shell dredgers

These are also commonly called lift excavators and use multiple buckets to remove material. All of these buckets are attached to an oval-shaped ladder. The ladder then moves like a caterpillar’s track, hitting each bed bucket and removing material. The material is then automatically discharged during the rotation process. This process continues until the ladder is closed.

The obvious advantage of a ladder dredger is that it facilitates rapid dredging. They are primarily used by mining companies to extract minerals and are usually attached to ships.

Sand Dredgers

As the name suggests, this type of dredger is primarily used to transport sand. Sand dredgers can be mechanical or hydraulic, with hydraulic dredgers preferred when transporting fine materials. Mechanical dredgers can be equipped with a number of attachments, including buckets, nets, and blades.

These dredgers are primarily used in the construction industry, as sand is an important component of many building materials. Interestingly, China currently uses sand dredgers extensively to dredge sand from Taiwan’s waters, degrading Taiwan’s waters and providing China with valuable sand in the process.

Hydraulic Dredgers

Next, we turn to hydraulic dredgers, which are less common than mechanical but still widely found in oceans, rivers, and lakes.

But what are hydraulic dredgers? Well, they use suction to remove material from the bottom, sometimes with the help of water jets. A pipe is lowered from the dredger to the bottom of the water. A pump then causes the material to be sucked in through the tube. The material can then be unloaded onto a barge or sent through a pipe to somewhere else.

Hydraulic dredgers can be fixed, portable, and self-propelled. Like mechanical dredgers, there are many hydraulic dredgers, and we explain the most common types below.

Conventional Suction Dredgers

Conventional suction dredgers use a tube that is forced into the material and then sucked in, sometimes with the help of water jets. All recovered material is then placed on a barge or sent directly to a recovery area.

Conventional suction dredgers are primarily used to remove sand and silt and can reach material more than 300 feet below the water level. Land reclamation projects heavily use conventional suction dredgers, but they are also used to collect sand to make concrete.

There are three different types of conventional suction dredgers. Standard suction dredgers of this type operate in exactly the same way as previously described, while deep suction dredgers are used in deeper waters, usually more than 100 feet deep. Suction dredgers have a shovel-shaped nozzle that allows the shovel to make different types of cuts in the material.

Suction-cutting excavators (often shortened to CSD) work in much the same way as regular suction excavators. Still, with one big difference: they have a cutting tool, usually an oscillating arc, attached to the tube head that loosens the material so that it can be easily sucked into the tube.

As you can imagine, this type of excavator removes solid material, such as rock. It is widely used in large projects, including large sand and gravel dredging, deepening seaways, and land reclamation.

Tracked hopper suction excavators

Tracked hopper suction excavators (often referred to as TSHDs) are self-driving excavators that look like large ships and small boats. These dredgers move at very low speeds (usually around 2 to 3 knots) and have three main parts: a pipe for removing material, a hopper, and a mechanism for dumping the collected material. This type of dredger is mostly used in high-traffic areas such as ports.

The bulldozer moves automatically in a designated area, pulling the pipe. The tube collects materials, mainly silt, sand, fine clay, and gravel, and stores them in a hopper. The largest TSHD has a capacity of about 30,000 cubic yards. When the hopper is full, the tube rises, and a bulldozer transports the material to a designated location where it is dumped.

Water injection dredgers

A water injection dredger is a specialized dredger used for environmentally challenging projects. They can also be used in smaller ports for regular dredging duties. No suction is involved in operating this dozer; in fact, the dredged material never even rises above the waterline.

So how do they work? Powerful jets of water are injected underneath the material to be shoveled, causing it to move. Much of the material mixes with the water in a liquefaction process and is carried away by the tide, which means that the dredged material does not need to be transported.

Choosing the Right Type of Dozer

Now that you know ​​the most common types of dredgers, you need to ask yourself: which dredger will best suit your needs? When deciding, there are several factors to consider: material transport, ship transport, location, dredged material, environmental and economic aspects. Let’s look at these four in more depth.

Material Transport

Where does the scooped material go after it is removed from the bed? Will you be working in open water and must use a barge to transport the material to another site? Or will it be closer to the ground, meaning the material can be transported by pipeline?

Ship Transport

Before you start shoveling, you will need to secure your dozer in place. It would be best if you rent additional marine vessels, such as a tugboat, using a portable dredge. However, if you use a self-propelled dredger, you will not need an additional vessel.

Location

Where is the material that needs to be shoveled? A fixed dredge may be a burden if you work in a port or other high-traffic area, meaning a TSHD may be a better choice. A bulldozer may be the smartest choice if you are working in a small space.

You should also consider the depth of the water. Are you dredging in deep water? If so, you will need a long-distance dredge, such as a deep suction dredge.

Material that needs to be shoveled

Different bulldozers transport different materials, and choosing the right option is crucial. Are you shoveling a hard rock? If so, a cutter suction dredger may be suitable. Do you want to remove soft slime? In this case, a simple suction dredger may be the best choice.

Maybe you don’t even want to engage in typical shoveling activities. Or, you may participate in marine rescue or mining. These also require specific features of the bulldozer.

Environmental

Environmental protection is becoming increasingly important, and harming the environment unnecessarily can reflect very badly on a company. Therefore, you should consider your environmental impact. For example, you can choose to use a water injection dredger to reduce your environmental impact.

Financial Aspects

Your financial situation will also play a big role in the type of bulldozer you choose. In short, some bulldozers are worth more than others, so the rental cost will be higher. You must also consider crew requirements and other expenses, such as transportation and unloading costs for cleared materials. Also, is the bulldozer you need located near you, or will you have to pay to have it delivered to your location?

If you will be using the bulldozer for a long time, buying it rather than renting it may be a better option. If you choose this option, consider factors other than the purchase price, such as maintenance, fuel, insurance, crew management costs, and vessel mooring if necessary.

Conclusion

As you can see, buckets come in many shapes and sizes, each with its own uses. The type of drill bit you choose really depends on your specific requirements—there is no one-size-fits-all solution, so you need to put a lot of thought into the types of drill bits available to you.