I want to know what the principle of underwater welding is

Is what’s described here sufficient? http://bbs3.zhulong.com/forum/detail1902081_1.html

Underwater welding can generally be classified into three categories based on the specific environment in which it is carried out: wet underwater welding, dry underwater welding, and partial dry underwater welding. 1. The method of welding the joints of welded parts in a wet state without employing any special drainage measures is known as wet underwater welding. For example, underwater stick arc welding is a typical form of wet underwater welding. The basic principle of this method is that when the electrode comes into contact with the workpiece, resistive heat vaporizes the water around the point of contact, creating a gas phase zone. As soon as the welding electrode moves slightly away from the workpiece, the arc ignites in the gas phase region; the heat from the arc then vaporizes a large amount of water present in that area. Together with the gases produced by the electrode coating, this creates a gas pocket of certain size around the arc, known as the arc cavity, which separates the arc and the molten pool formed on the workpiece from the water. It can be seen that the combustion of an arc in water is essentially the same as its combustion in the atmosphere; both are cases of gas discharge, with the only difference being the composition and pressure of the gas surrounding the arc. The heat from the arc causes water vapor to emit or ionize into gases, thereby causing the arc cavity to grow larger. However, once it reaches a certain size, it begins to rupture; some of the gases escape in the form of bubbles, and the arc cavity shrinks. Then, the gas generated by the arc heat causes the cavity to expand, and this process repeats itself. The arc cavity remains in a sub-stable state, with the arc burning within this sub-stable cavity, thus completing the welding process. 2. Dry underwater welding: a method in which gas is used to remove the water surrounding the welding area, allowing the diver welder to carry out welding in completely dry or semi-dry conditions. When performing dry underwater welding, it is necessary to design and manufacture complex pressure chambers or workspaces. 3. Local dry underwater welding: A method in which the diver welder and the workpiece are directly in water; a specially designed drainage cover is placed over the area to be welded, and air or a shielding gas is used to remove the water from within that cover, thereby creating a local gas-filled space for welding. Safety and protection for underwater welding: 1. Safe current level – In China, the safe current threshold for direct passage through the human body in underwater welding is 9 mA for alternating current at power frequency, and 36 mA for direct current. 2. Safe voltage: In China, the safe voltage for direct contact with the human body underwater is 12V for alternating current at line frequency, and 36V for direct current. 3. Safe distance from live conductors: When welding underwater, the electric potential gradient caused by leakage currents from welding electrodes and similar devices, as well as the current that enters the human body, are extremely weak; therefore, there is no safety issue, and generally no specific requirements are set for the safe distance from live conductors. 4. Location of the ground wire: Divers performing welding should face the grounding point and position the working area between themselves and that grounding point. Measures to prevent electric shock: 1. Direct current should be used for underwater welding; alternating current is prohibited. 2. Control electrical equipment that comes into direct contact with divers must use isolation transformers and have overload protection. It must not exceed the safe voltage level. 3. Regularly check the insulation and waterproof properties of equipment used underwater, as well as welding torches and cables. 4. When performing welding underwater, divers must wear special protective clothing and gloves. 5. Before starting work or during the process, if it is necessary to replace welding rods or cut welding wire, it is essential to inform those on land to disconnect the electrical circuit. 6. During arc initiation and maintenance, avoid having both hands in contact with the workpiece or the ground wire. 7. Be careful with the position of the ground wire; do not place yourself between the working area and the ground wire. 8. When performing underwater welding on structures that are under electric current (structures protected by external current), the electricity supply to those structures must be disconnected first. Occupational safety: In addition to complying with diving regulations and rules related to occupational health and safety in diving, divers must also pay attention to protection measures when welding underwater, especially regarding eye protection and protection against burns. 1. For eye protection, wear appropriate goggles. 2. To prevent burns, it is strictly forbidden to touch hot welds, welding rods, etc.; also, make sure that diving equipment and air tubes are not located in areas where hot substances may be sprayed.

I’ve learned it, but there’s still one question: what exactly is underwater cutting?

The 3rd floor is really professional; thanks, it was very informative

We generally use wet underwater welding.

The principles of underwater cutting and underwater welding should be the same; it’s just that the welding torch is replaced by a cutting tool.

Underwater welding comes in three types: dry method, wet method, and partial dry method. 　　(1) Dry welding: This method involves using a large gas chamber to enclose the workpieces, with the welder performing the welding inside this chamber. Since welding takes place in a dry gas environment, it is relatively safe. At depths beyond the range where air exists, sparks are likely to be generated due to the increased pressure of local oxygen in the air environment. Therefore, inert or semi-inert gases should be used in the gas chamber. During dry welding, welders should wear special fire-resistant and high-temperature resistant protective clothing. 　　Compared to wet welding and local dry welding, dry welding offers the best safety levels, but it has significant limitations in terms of usability, which is why it is not widely used. 　　(II) Local dry welding: Local dry welding is an underwater welding method in which the welder performs welding underwater while manually removing the water from around the welding area; its safety measures are similar to those of wet welding. 　　Since local dry methods are still under research, their use is not yet widespread. .320 – (III) Wet welding: Wet welding is a method of underwater welding in which the welder performs the welding directly underwater, without manually removing the water from around the welding area. 　　Arc combustion underwater is similar to submerged arc welding, as it occurs within bubbles. When the welding rod burns, the coating on it forms a sleeve that keeps the bubbles in place, thereby stabilizing the arc, as shown in Figure 8-1. To ensure stable combustion of the welding rod underwater, a layer of flux of a certain thickness must be applied to its core, and the rod must be made waterproof by impregnating it with paraffin or other water-resistant substances. Bubbles are composed of hydrogen, oxygen, water vapor, and bubbles generated by the combustion of the welding rod coating ； Other oxides produced by the turbid smoke. To overcome the difficulties in arc initiation and maintenance caused by water cooling and pressure, the arc initiation voltage must be higher than that in atmospheric conditions, and the current is 15% to 20% higher than that used in welding under atmospheric conditions. 　　Underwater wet welding is the most widely used compared to dry welding and partial dry welding, but it has the lowest safety level. Since water is conductive, preventing electric shock becomes one of the main safety concerns in wet welding. Causes of accidents in underwater welding and cutting The hazards associated with underwater welding and cutting are characterized by the use of an arc or gas flame underwater, which poses a greater risk compared to welding in atmospheric conditions or ordinary diving operations. 　　Common accidents in underwater welding and cutting operations include electric shock, explosions, burns, scalds, drowning, crush injuries, as well as deaths or injuries caused by decompression sickness or asphyxiation. The main causes of such accidents are as follows: (1) Ships or other objects that have sunk underwater often contain ammunition, fuel containers, and chemical hazards; if work is carried out without first checking these conditions, explosions can occur during welding or cutting operations. 　　(2) Accidents occur due to tempering and scalding of the operator by hot metal droplets, or damage to breathing apparatus and diving gear such as wetsuits. 　　(3) Electric shock caused by insulation damage or improper operation. 　　(4) Collapses of underwater components can lead to injuries such as bruises, crush injuries, or even death. 　　(5) Drowning accidents caused by damaged air supply pipes, scuba suits, electric shocks, or sea storms. Safety Measures for Underwater Welding and Cutting (I) Preparation Work An important feature of ensuring safety in underwater welding and cutting is the need for extensive and diverse preparation work, which generally includes the following aspects: (1) Investigating environmental conditions such as weather, water depth, water temperature, and flow rate in the operation area. Operations can be carried out only when the wind force on the water surface is less than level 6 and the flow velocity at the operation site is less than 0.1 to 0.3 m/s. 　　(2) Before underwater welding or cutting, it is necessary to determine the nature and structural characteristics of the component to be welded or cut, as well as to check whether there are any flammable, explosive, or toxic substances present within it. Objects that may fall or collapse should be properly secured, especially during underwater cutting, to prevent damage to the air supply pipes and cables.