Underwater-welding for saving while rescuing:
SOLUTIONS with Effective, Powerful Advice
Should I take the plunge?
Underwater-welding , enclosure welding, hyperbaric enclosure welding, wet Underwater-welding, high pressure water jet welding, other welding processes: friction welding, resistance welding, arc welding, tig welding, mig welding, oxyacetylene welding, electron beam welding, laser beam welding, welding techniques, welding information, welding links, welding tips, welding instructions, improving welding results, welding safety issues, joining questions needing answers: these are some of the items developed in this Site for the benefit of interested readers.
What is in here for me?
Underwater-welding, one of the best examples of adapting a well known process to the harsh and dangerous environment of the sea, demonstrates what necessity, ingenuity and continuing efforts could accomplish, mostly to save huge investments in offshore structures that were damaged and needed repair.
What is there, deep in the water? Does it pay?
The advantages are of economical nature, because Underwater-welding for marine maintenance and repair jobs bypasses the need to pull the structure out of the sea and saves much valuable time. If one thinks of Underwater-welding the hull of a ship or of a partially submerged oil drilling tower, one understands that the alternative may be extremely expensive, if at all possible.
The limitations of Underwater-welding concern the inevitable bulky and expensive setup to provide the welder with all the support needed, for respiration, for protection from cold, for special welding equipment, for remote surveillance camera, for special non destructive testing.
Is it risky?
The main risks for the welder performing Underwater-welding are the potential for electric shock, the possibility of producing in the arc mixtures of hydrogen and oxygen in pockets, which might set up an explosion, and the common danger sustained by divers, of having nitrogen diffuse in the blood in dangerous proportions. Curiously the risk of drowning is not listed with the hazards of Underwater-welding.
First there were no demands for quality. Underwater-welding was just applied to weld a patch until a more thorough repair could be performed. But as soon as more experience was gained, ambitious individuals and companies joined forces to improve results and to establish achievable specifications.
Let us continue…
… with some more details on Underwater-welding. There are three main ways to perform Underwater-welding. One is to build an enclosure, a pit, around the place of repair and to pump away all the water: that amounts to prepare the conditions for normal welding in air, although the place may be deep under sea level.
Another method of Underwater-welding consists in preparing an enclosure to be filled with gas (helium) under high pressure (hyperbaric) to push water back, and have the welder, fitted with breathing mask and other protective equipment, weld quite normally out of water but under pressure.
The third is the wet Underwater-welding method, where no attempts are made to dry up the location of welding. Instead the power of the arc generates a bubble of a mixture of gases which lets metal melting and joining occur more or less normally, using specially covered electrodes to avoid that too much hydrogen be absorbed in the weld. The skilled welder must also be a diver, equipped for Underwater-welding, with all the extra equipment and protection a welder must use.
There is also a less used method of Underwater-welding which features a special torch which sprays a cone of high pressure water, within which protective gas under pressure insulates the weld location from the water during welding.
Other Welding Processes.
Even if you are not familiar with Underwater-welding, you certainly know your processes. But how could a different one be selected?
By first knowing what other processes look like. One can certainly learn the most by enrolling in training courses, if it makes sense.
You know that there is no universal welding process perfectly adapted and convenient to whatever form and material joining. However in most cases one or more processes may be selected which permit acceptable welds to be performed.
How would you select your process? Is the process you use the best one? How would you improve on it? What is the best process?
Tip! : The « best » process is the the least expensive and available one that can be used to produce acceptable welds performing the functions of strength and stability required for the joint.
The following descriptive information of only the most important processes is provided for general orientation leaving more specific details to be found in the underlined referenced pages hereafter.
For practical purposes of designation, processes are usually divided between PRESSURE and FUSION WELDING. In the first type, pressure is always applied, with or without external means to provide heat, while melting temperature may or may not be reached. In the second type melting temperature is usually reached locally without the use of pressure.
Did you know that…
Welding history recognizes FORGE WELDING, which belongs to the pressure category, as one of the oldest processes performed in the blacksmith’s shop well before the twentieth century. Do you agree that it could be a very interesting experience for school-children to watch, if somebody wanted to revive the practice for a show? Would you organize that for your community?
This joining is achieved when two elements, usually steel bar ends, heated to white temperature in a coal burning forced air furnace, are brought rapidly together and hammered thoroughly on the anvil to expel any oxide layer which might be present and to work them intimately to complete union.
Similar but different…
A modern sophisticated version, called FRICTION WELDING was developed, which has some important applications, especially for mass production or for specialized repairs. In general it is not for job-shops, but small shops dedicated only to this specialty may thrive, given the right conditions.
Most important in the pressure category are RESISTANCE WELDING processes, further divided into spot, seam and projection welding, frequently highly automated. Many of our everyday household items and car bodies are held together by resistance welds. How would you decide if it is the right solution for your welding problems and how could you improve on it?
These processes share the fact that heating is produced by the resistance to the flow of a concentrated high electric current which is made to pass locally between special copper electrodes holding the elements to be welded together under applied pressure.
On the other hand…
Of the fusion welding processes developed in the twentieth century, and acclaimed as a real and important breakthrough, GAS WELDING, using an open FLAME, is probably one of the earliest of modern welding history. In this manual process the heat required for local progressive melting is provided by the flame of combustion of acetylene gas (other gases were tried and abandoned) with oxygen. A filler metal rod of appropriate composition may or may not be used as required.
In preparation for Underwater-welding there may be a need to perform flame cutting using hydrogen gas. (Flame welding is not used). See details in Cutting.
ARC WELDING represents a family of quite different processes, each one best adapted to its particular application niche. In these processes the energy required for melting the metals is provided by an electric arc, struck between the electrode, held by the torch, and the workpiece, usually clamped on a welding table.
Underwater-welding is mostly performed by variations on this process, taking into account the particular environmental and operator’s requirements.
In the general case, the electrode is either consumable, melting to provide filler material, or non consumable, being made from a refractory tungsten alloy. In this case, when needed, filler metal is provided separately either from a manually held filler rod or from a reel fed continuously in automatic or semi-automatic equipment.
The needed protective atmosphere is provided by gases from decomposition processes of suitable materials, enrobing the electrodes (sticks) or included in the core of specially prepared (flux cored) filler wires. Otherwise a stream of inert gas like Argon or carbon dioxide (CO 2) or mixtures thereof is continuously supplied to the molten pool through the torch.
Last but most important…
High Energy Welding processes are more specialized, in that they require sophisticated equipment, mostly precisely computer controlled, and are used for specific and important applications like aerospace, submarine (but not Underwater-welding!) and nuclear, or for mass production of delicate small implements.