Safe Practices for Underwater Cutting and Welding
Precautions with Cutting Equipment and Oxy-Arc Welding
- Ensure proper grounding of the generator and chassis.
- Prevent any terminal or group short circuits.
- Secure all electrical connections.
- Maintain a position on insulating surfaces, avoiding grounded metal.
- Wear undamaged rubber gloves or dry gummed canvas when handling electrical components.
- Control the group switching converter to minimize sparking.
Safety Switch
A self-regulated safety switch (300-400 amp) is mandatory for cutting and welding circuits. Approved safety switches, like machete switches, ensure current flow only during active operations. Adhere to these rules:
- Interrupt the current when not cutting or welding, or when the electrode is positioned for operation.
- Keep the switch open when not in use.
- For reverse polarity methods, use an automatic, single-travel, four-pole safety switch to open both work and ground cables simultaneously.
- Avoid using the switch in combustible atmospheres.
- Utilize only examined, tested, and approved safety switches.
- With single-pole switches, verify no bridging and ensure complete isolation of the cable between the converter and switch group.
- Prevent wet, damaged, or worn cables between the switch and converter to avoid short circuits.
- Position the switch for accessible operation by an assistant or supervisor, especially during underwater operations (except emergencies). Activate the circuit only upon the diver’s explicit instruction, confirming each change via intercom.
Safety Switch (Detailed)
This power failure device isolates the current flow to the diver in welding circuits. It features open/closed positions, or a switch/contactor for secondary power control. The diver must have absolute control over circuit activation. Also known as a machete switch, it protects against electric shock during cutting or welding.
Figure 3.8 illustrates a typical four-pole safety switch for underwater applications. Single-pole machete switches should be placed on the ground wire, with a lever handling the maximum welding current. Mount the switch vertically on a non-conductive material (wood, plastic). The open-circuit potential across the poles is approximately 80 volts. Enclose the switch in a non-conductive, covered box to prevent accidental contact.
Wetsuits
Maximize protection against electrical shock and arc eye damage. Drysuits, including gloves and masks with internal mouthpieces, are generally recommended. Observe these precautions:
- Avoid body contact with grounded work when the safety circuit is closed and a stripped electrode could contact the diver.
- Maintain complete isolation from all electrical circuits, including torches, electrode holders, grounded workpieces, and electric igniters.
- Use standard wetsuits only in good condition, with intact cellular structure and no tears or defects compromising insulation.
- Gas torches can be used underwater without protective gear, but electric igniters require standard safety precautions and rubber gloves. Gloves and goggles are mandatory on the surface.
- Rubber gloves or canvas-sticker gloves are required.
- Use a welding shield with appropriate lenses for underwater conditions during cutting or arc welding.