Development of small-sized models of low-cost alumina ceramic pressure-tight housings for ocean-bottom seismometers

Ceramics have some outstanding features needed for pressure-tight housings of underwater devices such as higher compressive strength, lower specific gravity and high resistance against corrosion. One of promising applications is pressure-tight housings for free-fall pop-up Ocean-Bottom Seismometer (OBS) because we can develop light and hard pressure-tight housings using made of ceramics, which have enough buoyancy even for deeper water application. In this paper, the results of Finite Element Method (FEM) analyses and hydraulic pressure tests of a small-sized model of ceramic sphere pressure-tight housings for OBS will be presented. Its rated hydraulic pressure is 80 MPa. In order to reduce the cost of production, we used alumina ceramic rather than silicon nitride ceramic with which we have already developed a ceramic pressure-tight housing for OBS. The results show that using alumina ceramic, we will be able to develop alumina ceramic pressure-tight housings for OBS having high reliability and applicable to deeper water than 8,000 m in depth.