Study on spherical pressure vessel of ceramics for deep-sea buoyancy module applications

Remotely operated vehicles (ROVs) for deep-sea operation should be as light as possible for Improvement of maneuverability and payload increase. Engineering ceramics has been one of the candidate materials for deep-sea pressure vessels because of its high compressive strength. The plan, which lessens its specific gravity and enlarges its pressure tolerance, had been prepared with installation of ceramic macro-spheres into syntactic foam, however it had failed due to the chain reaction of collapse of the ceramics macro-spheres. The main purpose of this study is to establish the methodology of fabricating the ceramic pressure vessels for deep-sea operation. As the first step, the spherical pressure vessel of ceramics was studied for deep-sea buoyancy module application. It is very important to keep the reliability on the macro-sphere, and the shape (=sphericity and thickness) should be controlled as good as possible. Thus, the ceramic hemispheres were fabricated, and their local radius of curvature and wall thickness was precisely measured by use of the simple measuring instruments. The measured results showed that the spherical irregularities were significantly improved compared with the sample of approximately 20 years ago.