Under Water Welding
The direct introduction of arc in water, in order to join the material underwater. Specially designed equipment is applied for this job; including water proof electrodes and power supply system. A welder dives into the water to weld and directs the operator to open or cut off the current supply when required. In this process an arc produced from torch, enables to heat welding electrode and work metal and facilitates the transfer of molten droplets through gas bubbles. Slag formation as a result of flux melting, helps to monitor the cooling rate as required in underwater conditions.
In order to achieve sound and quality welds, dry hyperbaric welding procedure is preferred to underwater welding. Because in later case it is difficult to ensure the quality control requirements. However research has made it possible by some sort of non-destructive examination techniques.
Use of dry chambers to provide safe and isolated environment to weld underwater. These specially designed chambers provide not only a pleasant environment to breathe in but also a clean environment by regular discharge of hazardous gases, which are produced as a result of welding procedure. All types of arc welding process; Tungsten Inert Gas welding, Shield Metal Arc Welding, Metal Inert Gas Welding, Flux cored Arc Welding, can be utilized in this technique but on the other hand, elevated pressure may cause problems. Thus hyperbaric welding process is limited to particular depth of water where a welder can sustain himself to operate easily without any operational problem (happens at elevated pressure).
Another type of underwater welding is Dry-Wet welding process in which the welder dives inside the water while the part to be welded, is enclosed in small dry chamber. In this technique, specially designed enclosures are being used to keep the welding equipment and components to be welded, in dry condition. Pressure of shielding gas is kept high as per requirement of working level in water in order to provide adequate protection and also to expel water out to avoid any contact.
Most commonly used arc process Gas Metal Arc Welding (GMAW), is applied for dry-wet technique to weld under water up to 120 ft. The welder can easily see and manipulate the arc in enclosures by properly adjustment of gun. Highly trained welders are required (both as a welder and diver) for dry-wet welding who must be aware of safety precautions and high pressure problems. This technique don’t require large expensive dry chambers like used in hyperbaric welding. On the other hand it also helps to provide more quality welds when compared to wet under water welding.
Under water welding is applied in marine applications and for the installation of offshore oil pipelines. It is also used to apply weld repair on massive ships inside the water. Well the process is easy to operate at shallow depth while it is found more onerous when the pressure increases at considerable depth.
Safety considerations for underwater welding
- The hazards may be of greater extent in case of under water welding. A welder may be exposed to severe electric shock. For this, welding equipment must be waterproof and insulated, and a sound communication is required between welder and surface operator, to monitor the current supply.
- An underwater welder must be fully trained with diving skills and complete awareness of diver’s diseases that may be caused by breathing in hazardous gases. The problem occurs when the concentration of dissolved inert gases into the body, is greater than equilibrium state, these gases tends to be come out with an indication of bubbles formation.
- A diver may experience the undesired effects of joint and muscle pain. Even the Decompression sickness may lead to death due to uncontrolled breathing gases. For this decompression procedure must be carefully monitored by using diving meter or computer.