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    • Cutting and Welding

    Cutting and Welding

    Cutting and welding equipment are crucial for underwater construction and repair in commercial diving operations. This category includes high-performance electrodes, cutting torches, robust welders and a variety of accessories support these tools.

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    Frequently Asked Questions

    An exothermic cutting rod does not rely on continuous electricity to melt metal. Instead, it uses a brief surge of direct current (DC) to strike an arc and ignite the tip of the rod. Once ignited, a flow of pure oxygen is pushed down the hollow centre of the rod. This oxygen fuels a fierce chemical reaction, causing the rod to burn independently at temperatures exceeding 5500°C. This extreme heat is capable of melting through thick steel, concrete, and marine biofouling, making it the most effective tool for underwater salvage and demolition.

    A safety knife switch is the most critical piece of safety equipment on the dive spread during underwater hot work. It is a large, manually operated electrical switch located on the surface, directly controlled by the dive supervisor or tender. The switch ensures the electrical circuit remains completely physically broken while the diver is moving or positioning their stinger. The supervisor only closes the switch, making the electrode “hot”, when the diver gives a clear, verbal command confirming they are stable and ready to strike an arc. This protocol prevents lethal accidental electrocution.

    The extreme heat generated by underwater cutting and welding separates the hydrogen and oxygen molecules in the surrounding water. If these highly explosive gases become trapped inside an enclosed space, such as a hollow structural pile or an overturned ship hull, a stray spark can trigger a devastating underwater detonation. Divers must meticulously inspect the work area and drill vent holes at the highest points to allow these trapped gases to safely bubble up to the surface before any cutting operations begin.

    No, you must never use a standard alternating current (AC) welding machine underwater. AC current can prevent a diver from releasing their grip if they receive an electric shock, which is almost always fatal in a submerged environment. Underwater welding strictly requires a direct current (DC) welding generator. The power supply must be paired with heavily insulated underwater cables, specialised waterproof stingers, and fully insulated wet welding electrodes to ensure the electric current travels only into the workpiece and not into the surrounding water.

    Wet welding occurs when the commercial diver and the welding electrode are directly exposed to the surrounding water. It is a fast, highly effective method for emergency vessel repairs, sacrificial anode installation, and general marine maintenance. Dry hyperbaric welding, by contrast, involves sealing a custom-built, water-tight habitat around the structure to be welded. The water is pumped out and replaced with breathable gas. While far more expensive and time-consuming to set up, dry welding allows for high-quality, code-compliant welds necessary for critical infrastructure like high-pressure offshore oil pipelines.