Using Excavator Sticks Underwater: Challenges and Solutions

[MikePhua]

Introduction
Excavators are incredibly versatile machines used in a wide range of construction, mining, and industrial applications. Their primary function is to dig and move material, but in certain situations, they must work in underwater conditions. Operating an excavator stick (the long arm of the machine) under water presents unique challenges that require careful consideration of equipment configuration, safety, and technical adjustments. Understanding these challenges and the solutions available can help operators maximize efficiency and ensure safe operations in underwater environments.

Why Use Excavators Underwater?
Excavators can be employed underwater for various tasks, such as dredging, underwater excavation, trenching for pipelines, or removing debris from bodies of water. In these applications, the excavator operates in a submerged environment, often performing tasks that are difficult or impossible with traditional equipment. The flexibility of excavators allows for a range of activities, from removing sediment to lifting heavy objects underwater, making them invaluable for aquatic construction and environmental projects.

Challenges of Working with Excavator Sticks Underwater
Operating an excavator stick underwater is inherently more complex than on dry land due to the following challenges:

1. Water Pressure and Buoyancy
   When an excavator works underwater, it faces the effects of water pressure, especially at deeper depths. Increased pressure on the stick can impact the force that the arm and bucket can exert. Additionally, water buoyancy can create an opposing force, making it more difficult to control and move the stick precisely. This can result in slower operations and more careful maneuvering.
   
2. Hydraulic System Strain
   Excavators rely on hydraulic systems to move their arms, stick, and bucket. Underwater, the hydraulic fluid is subjected to different conditions, including temperature and pressure variations. Special consideration must be given to the hydraulic system, as it can be affected by the external pressure of the water, causing a reduction in efficiency or potentially leading to failure if the system isn’t properly sealed.
   
3. Limited Visibility
   One of the most significant challenges when working underwater is reduced visibility. In many cases, the operator is unable to directly see the work area, especially in murky waters. This makes it difficult to control the excavation process accurately and safely. To overcome this, operators often rely on underwater cameras or remotely operated vehicles (ROVs) that relay visuals back to the surface, helping them guide the excavator's movements.
   
4. Corrosion Risks
   The constant exposure to water increases the risk of corrosion on the excavator components, particularly on parts that are not designed to withstand long-term submersion. Excavator sticks, hydraulic lines, and buckets can become corroded over time, leading to expensive repairs and potential breakdowns. Rust inhibitors and protective coatings are often used to extend the life of the equipment in such environments.
   
5. Debris and Sediment
   Underwater environments, especially rivers, lakes, and oceans, often contain large amounts of debris or soft sediments like mud and silt. Excavator sticks can struggle to maintain their precision when dealing with thick, sticky materials. The sediment can clog the bucket or prevent the operator from moving the material efficiently. The equipment must be equipped with special tools or attachments to handle these challenges.
   

Technical Adjustments and Solutions for Underwater Work
There are several methods and technological improvements designed to mitigate the difficulties of working underwater with an excavator stick. These solutions allow the equipment to perform efficiently in challenging aquatic environments:

1. Hydraulic Power and Pressure Control
   To counteract the impact of increased pressure underwater, excavators can be fitted with special hydraulic systems designed to maintain their power at depth. These systems are more robust and equipped with pressure-relief valves to manage high-pressure environments. Additionally, specialized fluid is used to maintain hydraulic system functionality and prevent fluid contamination.
   
2. Waterproofing and Seals
   Excavators working underwater need to have enhanced sealing on their hydraulic systems and electrical components to prevent water ingress. These seals protect the machinery from water, ensuring that the equipment continues to operate as it would on land. Waterproof coatings and corrosion-resistant materials are essential for all exposed parts, particularly the excavator stick and bucket.
   
3. Extended Reach and Heavy-Duty Attachments
   When working underwater, the stick and boom must have an extended reach to access deep areas or areas that are far from the excavator itself. Heavy-duty, specialized attachments such as dredging buckets, grapples, and clamshells are commonly used to assist in underwater excavation tasks. These attachments are designed to handle the increased pressure and offer better material handling capabilities, including the capacity to move sediment or lift heavy underwater materials.
   
4. Underwater Camera Systems and Remote Operation
   To combat the issue of visibility, modern excavators can be equipped with underwater camera systems or even remotely operated vehicles (ROVs) that provide real-time visuals to the operator. These systems allow the operator to view the underwater environment, adjust movements, and make necessary corrections to avoid accidents or inefficiencies. In some cases, the excavator may be operated remotely using these camera feeds, making operations much safer and more efficient.
   
5. Material Handling Modifications
   Specialized buckets and attachments are crucial for underwater work, particularly in environments with a lot of debris or soft material. Excavators often use "dredging buckets" designed to scoop up large quantities of silt, mud, or debris in underwater excavations. These buckets are reinforced to handle underwater conditions, and some are fitted with automatic debris-release mechanisms to keep the bucket clear of material buildup.
   

Case Study: Underwater Excavation for Pipeline Installation
A real-world example of underwater excavator use is in the installation of underwater pipelines. In these projects, excavators are often employed to trench along the seabed, preparing the ground for pipeline placement. The excavator stick must reach significant depths while lifting and moving debris, and it is crucial to control the movement of the bucket accurately to avoid disturbing the surrounding environment. Specialized dredging equipment and the use of underwater cameras are essential in such applications.
For this purpose, excavators like the Caterpillar 320C or similar models equipped with underwater capabilities are used. These machines are outfitted with robust hydraulic systems and reinforced bodies, enabling them to work efficiently in depths that would otherwise be inaccessible for standard construction equipment.

Safety Considerations for Underwater Excavation
Working underwater with an excavator stick requires stringent safety protocols:

1. Monitoring Pressure and Depth
   Operators must ensure that the machine does not exceed safe working depths, as the pressure can damage the equipment. Depth gauges and monitoring systems are critical to prevent these accidents.
   
2. Environmental Awareness
   Operators should be aware of the environmental impact of their actions, ensuring they do not disturb marine life or ecosystems. Using specialized tools like clam shells or buckets with fine control helps minimize disturbance.
   
3. Safety Equipment for Operators
   Operators working with underwater excavators should wear appropriate safety gear, including dive suits if they need to enter the water for inspections. Emergency protocols must be in place, especially for operators working in deep water or with limited visibility.
   

Conclusion
Excavator sticks designed for underwater work are indispensable for projects that require excavation beneath water surfaces, including dredging, pipeline installation, and underwater construction. The challenges of working underwater—such as water pressure, visibility issues, and the risk of corrosion—require specialized equipment, technical adjustments, and safety protocols. With the right modifications, training, and equipment, excavators can perform effectively in these challenging environments, making them invaluable tools for aquatic construction projects worldwide.