Welding Technology Archives

In this article, we will learn underwater welding, along with definition, working, types, challenges, applications, advantages, disadvantages, etc. Let's explore! What is Underwater Welding? Definition Underwater Welding Basics Underwater welding is a dangerous profession. It takes practice and experience. Apart from this, learning the process requires enrollment in a welding school. Such schools provide proper training under skilled instructors. The second step is getting into a certified driving school to learn diving. The whole process takes years. Not only proper training but experience and practice afterward is significant to become proficient. Underwater welding definition working types applications These are the main reasons that underwater welders are paid quite well. The Bureau of Labor Statistics has concluded that their hourly pay is about $28. Moreover, the job opportunities are rising at a rate of 9.5%. Salaries are rising at a rate of 3.5 %. Expert and skilled people are earning $100,000 yearly, which can go up to $150,000. It is one of the highly paid jobs without a college degree but involves a huge risk. Underwater Welding Definition Underwater welding is a high-pressure welding technique. It involves a person diving into the water to perform welding similar to on-ground welding. When it takes place in a dry environment, it is termed Hyperbaric welding. In the case of a wet environment that is underwater, it is called underwater welding. It is similar to welding on the ground. The techniques, basics, and equipment remain the same for both. However, underwater welding is a comparatively challenging and demanding field. History of Underwater Welding Before the 20th century, diving has existed for hundreds of years, but underwater welding was invented in the 1930s. The inventor was a Soviet engineer named Konstantin Khrenov. He put forward that underwater welding results in the frequent discharge of gas bubbles at the contact point with metal and arc. This issue leads to porosity in welds. Khrenov and his team introduced waterproof coating for electrodes. They performed a successful test in 1932 at the Black sea. The Soviets started to use it soon after its success. In the 1940s, Cyril Jenson, inspired by Konstantin, began his welding tests. Jenson expanded the underwater welding programs in the United States. He also introduced the arc-oxygen underwater cutting process. Underwater Welding: How it Works? Underwater welders make use of various options to perform welding tasks. Prior planning is a requirement before proceeding to ensure work safety. The main purpose of underwater welding is the repair and maintenance of marine structures. There are two types of workers. Those concerned with repairing dams, bridges, and small sea crafts are known as Hyperbaric Inland Welders. Those working on ships, underwater habitats, nuclear power facilities, and pipelines are offshore welders. The repairs are needed due to marine accidents or corrosion. The welding takes place at about 30 to 400 feet of salinity water. To understand clearly how underwater welding works, let’s get into the two main types. Major Types of Underwater Welding The two main types are wet welding and dry welding. Wet Welding Wet welding is defined as the process during which the site is surrounded by water. It is based on creating an electric arc between an electrode and the point to be welded. A common wet welding method is Shielded Metal Arc Welding (SMAW). It is widely used and is cost-friendly. During the process, to prevent hazards, ensuring safety is important. The surroundings are checked for any hazards before beginning the procedure. A layer of gaseous bubbles is created, which covers the weld. It prevents the contact of electricity with water and other corrosive or oxidizing agents. These safety measures are taken to keep the welders safe from being electrocuted. Wet welding is also carried out by other techniques like Friction welding and FCAW (Flux-cored arc welding). Dry Welding Dry welding is defined as the process during which the site is not wet and is separated from the water. It is also known as "habitat welding." It makes use of a hyperbaric chamber. First of all, a seal is created around the area that needs welding. Then, hoses are connected to push the water out to replace it with a mixture of gases like helium and oxygen. The chamber is pressurized to an appropriate depth which maintains a normal pressure hence preventing decompression sickness. The methods used in dry welding are dependent on the size of the hyperbaric chamber. Other techniques are habitat welding, pressure welding, dry chamber welding, dry spot welding. Besides, shielded metal arc welding and flux-cored arc welding (wet welding techniques) are also applicable. The current required for wet welding is 300-400 ampere. Techniques used in Underwater Welding The techniques used in underwater welding are discussed below. Each of them is used depending upon the repair as well as their limitations for the best outcome. GTAW (Gas Tungsten Arc Welding) It is also known as inert gas tungsten welding. It is most commonly used—the best and defects-free for welding metal to metal. The process needs a skilled person because it’s a bit complicated. It begins by forming an arc between non-consumable tungsten electrodes and the welding spot. It results in high-quality welds but demands precision. The welder holds a torch with one hand and introduces a filler rod in the weld pool with another hand. At the same time, welders control electric current to weld puddles through a foot pedal. So it's multitasking work that needs to be on point. GMAW (Gas Metal Arc Welding) This process involves forming an electric arc between a metal inert gas wire electrode and a workpiece. It heats the area, joining both together. At the same instant, a shielding gas is introduced that prevents atmospheric contamination. There are four ways to carry out the metal transfer in GMAW; globular, spray, pulsed spray, short-circuiting. Each of them differs in terms of advantages and drawbacks. FCAW (Flux-cored Arc Welding) In this process, an electric arc produces heat that fuses base metal in the joint welding area. The filler wire is tubular cored and consumable. The arc causes filler wire and metallic workpiece to fuse, creating a weld joint. Instead of a solid metal electrode, FCAW uses a tubular, hollow electrode filled with flux. It is divided into two types; one relying completely on flux core for a successful weld while the other uses an external shielding gas. SMAW (Shielded Metal Arc Welding) It is an older and most commonly used technique of welding. Another name for SMAW is "stick welding." The weld is formed by connecting a power supply to a flux-coated electrode, a metal stick, or a rod placed in an electrode holder. Electricity touches base metal by passing through the electrode. The magnetic flux forms a shielding gas to protect the electric arc between the metal and the weld zone. PAW (Plasma Arc Welding) The process of PAW is similar to TIG. An arc is produced between a pointed tungsten electrode and a workpiece. The difference is that the electrode is positioned within the torch body to separate the plasma arc from the shielding gas envelope. The arc is constricted when plasma is forced through a fine-bore copper nozzle. Based on the rate of flow of plasma gas and the diameter of the bore, there are three methods to carry out PAW; Micro plasma welding, medium current welding, and keyhole welding. Pressure Welding This technique combines workpieces by applying a large force, also termed solid-state welding. The basic principle is the use of mechanical pressure. This process can include various methods like explosion, ultrasonic, diffusion, resistance, and friction welding. Dry Spot Welding It applies to small chambers where good sealing is ensured for carrying out this process. Welding is done by placing electrodes inside the chamber. Dry Chamber Welding It requires a small-sized chamber that accommodates only the upper body of the welder. A diver enters the chamber from the bottom. FCAW and SMAW are employed in dry chamber welding. Challenges in Underwater Welding The occupation of underwater welding is quite appealing with good wages. Despite this fact, it is very dangerous and risky even after experience and practice. These dangers may prove to be fatal, while others are known to cause long-term health problems. Some of these risks are explained below. Electric shock Electric shocks are the most common. Since water is a good conductor of electricity to result in electrocution, the welder needs to be experienced to properly fix the weld; otherwise, it can result in electric shocks because arcs are quite unstable. All the equipment is tested well for any defects before starting the process. They must be working properly and should contain a waterproof electrode. Explosions The mixing of hydrogen and oxygen forms hundreds of gas pockets. They can result in explosions if ignited. While performing wet welding, if popping sounds are heard, it indicates gas pockets formation. In this case, the welder should stop welding immediately, and the defective point should be located to avoid hazards. Drowning Even after acquiring all skills, drowning can be a cause for workers' death. Sometimes the equipment is faulty. The mask, oxygen tank, or any other equipment is faulty, which can cause trouble. In many other cases, underwater obstacles can also become an issue. Moreover, deep down, the visibility lessens, so a person cannot see clearly. All these factors can cause explosions. So, a thorough inspection of equipment must be made by the staff to ensure safety. Decompression illness Decompression illness is caused by nitrogen bubbles that enter the bloodstream. They result in adverse symptoms like rashes, joint pain, paralysis, and even death. Other symptoms are nausea, muscle fatigue, difficulty in thinking, and weakness. The bubble enters because divers sometimes move too quickly from high-pressure region to low-pressure region. Hearing problems The work is such that welders have to spend a lot of time in a high-pressure zone. It can affect ears causing permanent or temporary hearing issues. The high pressure may result in lung damage too. Long-term health problems Apart from ear, lung, and nose damage, chronic pain, lost limbs, lack of cognitive abilities, and memory difficulties later in life can also occur. The levels of oxygen are also low. The body is affected in many ways. Due to these reasons, the workers work in shifts so that no one stays underwater for a long period. Hypothermia The temperature in the water is very cold. Human bodies need a specific temperature for the organs to function properly. If the diver spends too much time in this cold area, it results in heat loss from the body, ultimately causing organ damage, loss of consciousness, etc. Properly insulated wet rubber suits will protect against extreme cold temperatures. If not, the welder will drown. Distractions Planktons are sometimes attracted to welding lights. The planktons will attract the fish. This disturbance can distract the welder and lead to a menace. Sharks and other dangerous underwater creatures can attack humans; therefore, the workers need to be very cautious. But the workers are constantly connected to the team and mostly have someone along with them to assist with the repair. Applications of Underwater Welding Underwater pipelines Underwater welding is necessary for the installation, maintenance, and repair of pipelines. Offshore oil drilling Crude oil is extracted from the sea bed. The setting for oil drilling comprises large machinery and equipment partially submerged in water. Welding has a huge application here. Shipyards Applications of welding can be found in shipyards or dockyards as well. These are areas where ships of all sizes are repaired and manufactured. Underwater power plants Nuclear power plants are not only constructed on the land. They are also present underwater to increase electricity production. Thus, the demand for underwater welding has increased. Mining Raw materials are extracted from sea beds. It's a huge industry. So. For smooth running, it needs underwater welding. Ships Large ships often need repairs in the submerged areas. Hence underwater welding is required. Advantages of Underwater Welding Dry Welding The whole process takes place in a chamber that is resistant to ocean currents and is well illuminated. It has an Environmental control system. It ensures the complete safety of workers.Non-destructive testing, also known as non-destructive evaluation, is based on analysis of techniques, materials, structures, welding defects, etc., without causing harm to the original part.High-quality welds are produced due to low levels of H2 and an ideal environment.Permanent welds with a better strength of the structure are achieved.NDT inspection, alignment of pipes, and monitoring other things.The equipment used is faster and easier to move.They are the best choice for emergency repairs.The danger of explosion is minimized to a larger extent.Welding complex structures will need customization to surround the entire area of the weld. It is cheaper and can easily be attained.A controlled environment enables even distribution of heat.Gas is delivered at a pressure higher than that of water, even at greater depth. It keeps the area being repaired dry.It is possible at and below the sea surface.Dry hyperbaric welding conditions are compared to underwater conditions for best results. Wet Welding It is used repeatedly and across the globe because of its low cost.Wet welding can be carried out with great speed. So, it saves time.Welding equipment of good quality is used.Building enclosures can waste time. It doesn't require enclosures. So the process is effectively and quickly carried out by machinery and equipment that are not too expensive.It is used in welding offshore structures that can’t be fixed using other procedures.Special techniques allow welding at a depth of 100,000 feet. Disadvantages of Underwater Welding Dry Welding The chamber is complex.Heavy equipment is needed, which is quite costly.Cost is high and increases periodically with depth.Arc constricts, and higher voltages are required at greater depths.The chamber used in one job cannot be used in other jobs. Every time a different one is constructed. Wet Welding Water quenches the metal weld continuously. Although quenches are known to increase the tensile strength of weld simultaneously, it decreases ductility. It leads to porosity and hardness of the metal.Water existence is a major concern.The welder cannot see properly, which affects the outcome.Due to water vapor dissociation in the arc region, a large amount of hydrogen is there in the welding area. This H2 enters the heat-affected zone (HAZ) and metal resulting in embrittlement, microscopic fissures, and cracks. The embrittlement can seriously damage the structure.Increasing depth, pressure, and temperature are factors contributing to cracks formation. Despite many advantages, there are plenty of disadvantages. Underwater welding exposes the workers to greater health risks and death in the worst circumstances. Conclusion There are numerous advantages and applications of underwater welding. Due to advancements in technology and science, it is very effective. Nowadays, its scope has tremendously increased. Despite being dangerous, this profession has a scope and is quite practical. Since welding underwater is quite dangerous therefore these welders are given high wages. The modern era has made it easier and safer to a larger extent, and the risks are reduced to greater extremities. There are various new techniques introduced to carry out the welding. Industries like oil drilling for extracting crude oil are growing rapidly. Industries play a substantial role in a country's economy. With all these factors, underwater welding is a vital and famous profession to pursue. It is much needed due to its diverse applications. Check out to our a few interesting articles,What is weldingArc weldingWelding defectsWhat is pumpProgressive cavity pumpGlove valvePiston pumpsReference Articles