Welding Underwater

Method of arc welding under water based on the ability of the arc burning steadily in a gas bubble under intense cooling of the surrounding water. The gas bubble is formed due to evaporation and decomposition of water vapor and gases and molten metal coating of the electrode.

Underwater Welding

Around the burning of the arc, a large amount of gases, which leads to increased pressure in the gas bubble and a partial release of gas bubbles on the surface of the water. Water decomposes in the arc of a free hydrogen and oxygen, the latter is connected to the metal, forming oxides. Suspended in water, the products of combustion of the metal and coating, consisting mainly of iron oxides to form a cloud of mist, which makes it difficult to monitor the arc.

Steady burning of the arc under water can be explained by the principle of minimum energy Steenbeck, ie, an increased cooling section of the arc is compensated by an increase in the number allocated to it energy. To compensate for heat losses due to the cooling effect of water and the presence of large amounts of hydrogen arc voltage under water requires a high (30-35 C).

Underwater welding is carried out on direct and alternating current. The dc arc is more stable than in AC, as a constant current decomposes the water even before the initiation of the arc, and an alternating current decomposes water and forms a gas bubble at the time of a short circuit under the action of heat.

With increasing depth, and ambient pressure of the arc resistance is not broken, only increases the voltage and current increases. Underwater welding is possible in the fresh river water and salty water. As sources of supply and use of single-station multioperator welding machines, welding transformers and transformers with open circuit voltage of 70-110 V.

Manual arc welding under water using electrodes with a diameter of 4-6 mm. Water-resistant coating is achieved by impregnating compositions such as paraffin, a solution of celluloid in acetone solution in dichloroethane resin, nitro, etc.

To use special underwater welding electrode that has a reliable electrical insulation over the entire surface. The change of the electrode is made only after switching off the welding current. Welding chain has forward and reverse cables.

When welding under water do lap joints, T-, angular, less butt, and often means relying electrode. Arc welder moves without hesitation across the joint while maintaining a constant angle of inclination of the electrode. Method based electrode can be welded joints in all positions. Welding in the vertical position produce a top-down, while the electrode is tilted to the side of welding.

Current strength in underwater welding electrode resting in the bottom position set higher than when welding under normal conditions. When welding in the vertical current is reduced by 10%, and in the overhead position - 15%.

Technique diver-welder weld under water is more complex than in air. This is due to poor visibility in the water tightness, heavy and awkward to move diving equipment, the need for additional costs to overcome the flow resistance welder's ability to breach on the ground, unsuitability of the human body to work at great depths. In this regard, the welds are frequently observed defects: lack of fusion of one of its edges, undercuts, nodules, pores, etc.

In addition to manual welding are used for underwater operations such as semi-PASR-300-2, "Neptune". Semiautomatic PASR-300-2 steel can be welded to a depth of 60 meters as protection use carbon dioxide. Semi is designed for a nominal strength of the current 300 A. In the MIG arc is stable suspensions formed small that almost does not prevent the observation arc.

Welding technology:

manual arc welding semi-automatic welding argon arc welding machine welding electroslag welding plasma welding laser welding electron beam welding

gas welding resistance welding spot welding seam welding projection welding butt welding welding underwater welding in space