Welding with a melting electrode in the underwater position can be performed on alternating and direct current. Underwater welding work A direct or reverse polarity direct current is usually applied, providing more stable arc burning and less power consumption and electrodes. Gorenje In addition, direct current when working in water is less dangerous for the human body. The choice of polarity depends on the type of work and the type of electrodes.
The physical process of underwater arc welding is similar to air welding, but the high density and thermal conductivity of the medium, as well as the difficulty of maintaining the arc, give it specific features. In addition, the welding arc under water is enclosed in a pulsating vapor-gas bubble, which is formed as a result of dissociation and evaporation of water, as well as combustion of the electrode coating and metal. The composition of the gas bubble is dominated by hydrogen (70-74%) and carbon monoxide (14-24%).
Higher current parameters than in air welding allow to compensate for energy losses on water electrolysis and due to the cooling effect of water and hydrogen, which has a high thermal conductivity at high pressure. To excite the arc, the source of the welding current at idle must have a voltage of 70-90 V, and to maintain the arc, a voltage of 29-35 V. the welding current also increases Significantly.
Specifications of electrodes for underwater welding
Electrodes for underwater welding are coated with a thick layer of refractory lubricant that meets a number of specific requirements. When the electrode melts, a 1.5-2.0 mm peak is formed, which helps to maintain the gas bubble near the arc and prevents short circuits, which is important in difficult underwater welding conditions.
Due to the deionizing influence of hydrogen, the value of components ionizing another space increases. The role of slag protection is limited compared to its role in the air, as the gas bubble contains a small amount of oxygen and nitrogen, and the cooling effect of the medium reduces the zone of thermal influence, although it makes it sharper. Thus, it is easier to ensure high quality weld weld metal. The coating, moreover, necessary requirements of water resistance. Its components must not contain water-soluble substances, leach or react with water. the coating is covered with a layer of waterproofing material (paraffin, celluloid, vinyl and other resins).
When working under water, electrical safety is of particular importance. Due to skin hydration and other reasons, the electrical resistance of the diver’s body is drastically reduced. In addition, due to the spread of current in an electrically conductive medium, the probability of closing the electrical circuit through the diver increases. In this regard, a voltage of more than 12 volts in water is a threat to human life. Deadly dangerous is considered to be 0.1 a current. These circumstances, as well as the inability to provide immediate assistance to the diver requires enhanced protective measures.
Underwater welding work
Electric holder for underwater welding
1)-rod bronze; 2)-bronze glass;3)-contact tip; 4)-cap textolite; 5)-handle textolite; 6)-rubber ring; 7)-brass ring; 8)-bushings steel; 9)-welding cable.
For underwater welding, electrode holders made of dielectric materials are used. Only flexible cables are used as welding cables. They are connected by quick couplings.
Equipment for underwater electro-oxygen cutting