In the commercial diving sector, underwater cutting (burning) and wet welding are staple activities. Yet, they remain two of the most hazardous tasks a diver can perform. The combination of high amperage, saltwater (a perfect conductor), and the diver’s position in the circuit creates a working environment where there is zero margin for error.
At iSubC, we supply the industry’s leading underwater cutting and welding equipment, from Broco torches to ultra-thermic cutting rods. However, supplying the gear is only half the battle. Knowing how to use it without destroying your equipment, or injuring yourself, is where the real expertise lies.
This guide outlines the critical safety protocols for underwater burning and welding, focusing on preventing electric shock and managing electrolysis.
The Physics of Danger: Understanding the Circuit
To work safely, you must respect the circuit. In topside welding, the air acts as an insulator. In underwater welding, the water surrounding you is a conductor.
When the arc is struck, electricity flows from the machine, through the cables, to the torch (stinger), through the electrode, across the arc to the workpiece, and back to the machine via the ground clamp.
The Danger Zone: If there is a break in the insulation of your cables, a tear in your rubber gloves, or if your body becomes a path of least resistance, you become part of that circuit.
The “Metallic Taste” Warning
One of the earliest warning signs of electrolysis or mild shock is a distinct metallic taste in the diver’s mouth.
- What it means: This indicates that electrical current is passing through the diver’s body, causing the fillings in teeth or metal bridgework to react.
- The Action: If you taste metal, stop immediately. Instruct the tender to open the knife switch (make it cold). Check your ground clamp connection and inspect your suit and gloves for leaks.
1. The “Knife Switch” Protocol: Your Primary Lifeline
The single most important piece of safety equipment in underwater burning is the Knife Switch (or isolation switch). This is a double-pole switch located topside, controlled entirely by the tender (or phone talker).
The Golden Rule: The welding lead must never be “hot” (live) unless the diver is in position and ready to strike the arc.
Never leave a switch closed while the diver is changing rods or repositioning. A live electrode touching the diver’s helmet or bailout bottle can be catastrophic.
2. Polarity Matters: Protecting the Diver and the Tool
Setting the correct polarity on your DC welding machine is not just about weld quality; it is a safety and equipment preservation issue.
For Underwater Cutting (Burning)
Standard industry practice for underwater cutting (using systems like Broco) requires DC Electrode Negative (DCEN), also known as Straight Polarity.
- The Setup: The Electrode (Torch) is connected to the Negative (-) terminal. The Ground (Work) is connected to the Positive (+) terminal.
- Why? In an electrolytic environment (saltwater), oxidation (corrosion) occurs rapidly at the positive pole (the Anode). By making the work positive, the corrosion attacks the scrap metal, not your expensive torch holder.
- Safety Implication: Using DCEP (Reverse Polarity) for cutting can destroy the internal collet of the torch in minutes due to electrolysis, potentially causing the rod to slip or the torch to fail during a burn.
For Wet Welding
Polarity for wet welding depends on the specific electrode being used.
- General Rule: Most wet welding electrodes run on DCEN (Straight Polarity) to extend the life of the electrode holder.
- Exception: Some high-strength electrodes are designed for DCEP. Always check the manufacturer’s data sheet (e.g., Broco or Hydroweld specs) before connecting the leads.
3. Combating Electrolysis
Electrolysis is the chemical decomposition produced by passing an electric current through a liquid or solution containing ions (like saltwater). For the diver, electrolysis is an enemy that attacks equipment.
The “Sacrificial” Plate
If the ground clamp is placed too far from the weld site, the current must travel through a large section of the structure. If the structure is painted or has marine growth, the current might seek an easier path, potentially through the water and the diver’s gear.
- Best Practice: Place the ground clamp as close to the work area as possible.
- Cleaning: Ensure the contact point for the ground clamp is scrubbed to bare metal. A poor ground connection forces the voltage to “hunt” for a path, increasing the risk of shock.
4. Essential Gear Checks: The Pre-Dive “Wiggle Test”
Before the diver leaves the surface, a strict inspection of the burning gear is mandatory.
- Insulation Integrity: Check the welding cables for any cuts or abrasions. Underwater, a tiny nick in the cable jacket leaks current into the water, reducing power at the arc and creating a shock hazard.
- The Torch: Inspect the flash arrester (if applicable) and the collet washer. Ensure the torch body insulation is not cracked.
- Rubber Gloves: Divers must wear heavy-duty rubber latex gloves over their thermal gloves. Even a pinhole can allow electricity to track to the diver’s hand.
- Eye Protection: Ensure the welding lens is the correct shade for the water clarity. Flipping a welding visor down in zero visibility is disorienting; ensure the diver is stable before “making it hot.”
Conclusion: Safety is a Team Sport
Underwater burning is efficient and essential, but it relies on a strict partnership between the diver and the topside team. The equipment – the knife switch, the DC welder and the torch must be maintained perfectly, but the protocols are what save lives.
Whether you are looking to upgrade your cutting torch inventory or need advice on the correct cables for deep-water burning, iSubC has the expertise and the inventory to support your operations.
Need certified underwater cutting equipment? Browse our range of Cutting & Welding Gear here or contact our team for advice on setting up a safe cutting station.
