Sustainable Subsea Pressure Housing for Shallow Water Applications

Abstract

The design of subsea pressure housing (SPH) with parameters such as hydrostatic external pressure, temperature and salinity prevailing in the marine environment requires a proper selection of materials. The housing is designed to accommodate the data acquisition electronics that is capable of handling a higher sampling rate and a larger capacity power pack for subsea ambient noise measurement mooring system operating at an ocean depth of 100 m in the shallow waters of the Indian coast. The scope of the housing design includes sustenance and operation of the system for a minimum of six months in an open ocean environment withstanding extreme events like cyclones and storm surges prevalent in the sea. The main aim of this paper is to present the work carried out on the design of SPH with three different materials such as high-strength stainless steel (SS316L), aluminium alloy (Al6061-T6) and titanium alloy (Ti-6Al-4V) for shallow-water applications. The design of SPH in a cylindrical shape with an internal diameter of 0.33m (330 mm) and length of 0.7m(700 mm) to withstand a pressure of 1MPa (10 bar) and hoop, axial and Von Mises stresses has been accomplished as per the American Society of Mechanical Engineers (ASME) code/standards. The buckling of cylindrical pressure housing and principle stresses were calculated through a finite element analysis (FEA) using ANSYS software.Further comparative studies on three materials mentioned above on the criteria of maximum stress, critical buckling pressure, formability, corrosive properties and cost of fabrication were carried out. The pressure housing with SS316L material is found to be an optimal choice for shallow-water applications in the open ocean. The subsea housing thus designed has been fabricated with SS316L and operated in the shallow waters of Goa successfully for a period of six months continuously.