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Geothermal Energy
Published in Robert Ehrlich, Harold A. Geller, John R. Cressman, Renewable Energy, 2023
Robert Ehrlich, Harold A. Geller, John R. Cressman
Spallation is the process by which fragments of a piece of material are ejected due to either impact or stress. Spallation drilling involves no drill bit that can wear out due to contact with the rock. Instead, a flame jet makes contact with a small area of the rock at the bottom of the borehole, and the induced thermal stresses in the rock cause small fragments of it (spalls) to be ejected.1 The fragments are small enough that the injection of high-pressure water carries them up the water-filled drilling pipe. Oxygen must be supplied to allow combustion underwater in a similar manner as done in underwater welding. The spallation technique has been demonstrated and found to work well, and it is likely to be a significant improvement over conventional drilling methods, in terms of both speed and cost—especially if it can make the cost dependence on depth linear rather than exponential (Figure 6.12).
Friction Surfacing of Metals
Published in B. Ratna Sunil, Surface Engineering by Friction-Assisted Processes, 2019
Producing underwater surface coatings is another development in friction surfacing research as demonstrated by Li and Shinoda [31]. Underwater welding and localized repairing of the surfaces is necessary to increase the life span of the offshore structures. In such applications, conventional fusion based welding processes are not effective due to the surrounding environment and different thermal events during solidification. Several studies on underwater friction welding demonstrate the advantage of adopting solid-state welding processes for offshore applications [31–35] used AISI 440Chardenable martensitic stainless steel with 1%C and 17% Cr as consumable rod and a low carbon steel (SM50C) as substrate and demonstrated underwater friction surfacing by using tap water as the medium. It was observed that the offset of the coating centerline with reference to the sliding axis of the rotating consumable rod was almost eliminated in underwater friction surfacing unlike in friction surfacing carried out in air. More uniform shape was observed for the deposited coating in the case of underwater friction surfacing. The deposition efficiency which is usually consumable rod rotation speed dependant was observed as less insignificant in the underwater compared with air. Additionally, the deposited surface layers exhibited uniform fine micro-structure and hardness distribution compared with deposits developed in air. From the overall findings, it can be understood that friction surfacing can also be used as a promising tool for underwater applications.
Geothermal Energy
Published in Robert Ehrlich, Harold A. Geller, Renewable Energy, 2017
Robert Ehrlich, Harold A. Geller
Spallation is the process by which fragments of a piece of material are ejected due to either impact or stress. Spallation drilling involves no drill bit that can wear out due to contact with the rock. Instead, a flame jet makes contact with a small area of the rock at the bottom of the borehole, and the induced thermal stresses in the rock cause small fragments of it (spalls) to be ejected.1 The fragments are small enough that the injection of high-pressure water carries them up the water-filled drilling pipe. Oxygen must be supplied to allow combustion underwater in a similar manner as done in underwater welding. The spallation technique has been demonstrated and found to work well, and it is likely to be a significant improvement over conventional drilling methods, in terms of both speed and cost—especially if it can make the cost dependence on depth linear rather than exponential (Figure 6.13).
Underwater wet FCA-welding of high-strength steel X70 through the use of flux-cored electrode
Published in Welding International, 2020
Underwater welding in the water environment is widely used for the installation and repair of oil and gas pipelines, oil and gas production platforms, surface and submarine ships, in the construction of berths and coastal structures. Research on wet underwater welding using coated electrodes [1,2] is well known. The development of technologies for wet underwater welding and an increase in productivity are associated with the solution of complex metallurgical problems of alloying, deoxidation of the weld, reduction of hydrogen porosity and slag inclusions [3–5]. To create reliable underwater welded structures with high performance, it is necessary to provide a high level of strength, ductility and impact toughness, in accordance with the requirements of regulatory documents [6].