Design peculiarities of sealing joints for cable penetrators

Abstract

The purpose of this work is to describe and summarize main design principles of sealing joints for cable penetrators of deepwater vehicles. The study was performed on typical sealed areas of watertight cable penetrators, like soldered joint between copper sheath of a heat resistant cable with mineral isolation (KMZh) and cable penetrator body; polymeric termination of cable ends; sealing joint of metal penetrator body in pressure hull with circular elastomeric gaskets. The case study in this paper is a metal casing attached to KMZh cable by a heat-resistant silverized brazing alloy. The quality of soldering joints was estimated metallographically, i.e. by means of optical microscopy and electronic raster spectroscopy. Watertightness of KMZh cable is ensured by reactoplast-based polymers that must be not only adequate to their operational conditions but also comply with fire safety regulations for ships. Watertightness of penetrator interface with pressure hull is achieved by means of elastomeric gaskets. The study investigated main sealing joints of penetrators, as well as the mechanisms achieving watertightness of each given joint. Analysis in ANSYS software package yielded the optimal thermal scenario of casing warm-up offering the best quality of both soldering process and adhesion to the KMZh cable. The calculation was also performed for the minimum length of brazed joint of constant width so as to ensure strength and watertightness at different external pressures. Calculation results were performed by hydraulic tests of penetrator samples. The study also identified the peculiarities of polymeric sealant selection. A promising approach for cable termination manufacturing would be to use heat-resistant materials featuring shape memory effect.