Overview of Underwater Repair – Blanking and Cofferdams

There is no questioning the fact that operating in or near-water is a complex and challenging task. If you are looking for cofferdams in underwater ship repair, you should know that these require adequate planning, highly qualified and experienced diving professionals, and correct gauging of the relevant environmental, safety, and water management concerns. We also have to consider unpredictable weather conditions when talking about underwater repair and cofferdams.

People prefer repairing and undertaking hull maintenance on sea or underwater because unscheduled dry-docking is usually a very expensive option and is only considered when there are no other options for the ship. In such conditions, the ship owners and managers consider dry-docking but, otherwise, they prefer to complete maintenance and repair on the sea. If you are looking for the best possible services, without impacting your vessel’s sailing schedule, we suggest contacting Nereus Subsea for underwater repair and maintenance services such as plugging, blanking, and the installation of cofferdams for more intrinsic and demanding requirements.

What is a cofferdam and how does it help maintain the integrity of your vessel?

During the process of underwater ship repair, a cofferdam acts as a temporary sealed-off space beneath the water surface, allowing repair and maintenance to be carried out in the other external parts without causing damage to the protected segments. The use of cofferdams also allows professionals to repair and maintain ships in dry conditions without needing to dry dock, making it a win-win situation for all the stakeholders.

Depending on the type of repair and maintenance required, there are several types of cofferdams and these are usually manufactured keeping the specific project requirements in mind. The installation and post-maintenance removal of the cofferdam can require the use of a crane and lift bags, based on the size of the installation. Professionals at Nereus Subsea, usually comprised of divers and welders, follow a project requirement-specific step-by-step method to ensure the best results for your vessel. In addition, we also ensure compliance with the strictest safety standards, as necessitated by the need for high precision in underwater works.

At Nereus Subsea, we usually follow a three-stage process to ensure optimal repairs. The first stage is the cofferdam ship repair pre-installation preparation. During this stage, we look at the structural drawings and consider the job scope from the client. In addition, we also analyze and measure aspects such as the area that needs to be covered by the cofferdam and, if standard devices do not match these requirements, we put in the order for a new and customized one. We also ensure that the new, customized cofferdam has lifting points, attachment points to hold cofferdam, suitable cavity dimensions away from the vessel’s hull, and drain/venting valves to ensure airflow. These features allow us to secure the cofferdam efficiently and ensure seamless repairs and maintenance.

What are the main stages of cofferdams in underwater ship repair?

The next stage is installing the cofferdam and, before the actual installation, our underwater diving inspection team carries out an initial analysis of the situation once this part is done, the dive team places the magnetic cofferdam in position to protect the area which needs coverage while aligning the inbuilt seals with the edge and positions. The seals are then coated with sealants as an additional proception measure and avoid problems. Plugs are then installed to drain the cavity. Once the draining is complete, the divers inspect for further leaks and confirm the completion of the second stage.

The third stage involves completing the required repairs and maintenance work and, after this is done, the cofferdam is removed in a process that reverses the installation procedure in an exact and timely manner.

installing cofferdams in ships

Sometimes, the ship may require repairs inside the cofferdam. In this situation, gas cutting methods are used to remove hull plates and cofferdams are used to replace these plates and maintain the integrity of the ship. For this purpose, the hull plates are measured optimally and cofferdams are created basis the exact measurements.

If you are looking for a professional team to help you with your cofferdam repairs and plugging needs, look no further. Nereus Subsea has a host of experienced divers and welders who are experts in their fields and who can help you complete underwater repairs and blanking without dry-docking or wasting precious time. Contact us for all your underwater ship needs and we assure you the best business in the industry.

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