Heat transfer tube for LNG vaporizer, its production method, and LNG vaporizer using such heat transfer tubes

摘要

A heat transfer tube for an LNG vaporizer in which damage in the surface of the Al alloy substrate by corrosion is effectively prevented even when it is used in the lower portion of the panel or in the lower header where the surface is vigorously cooled and formation of the oxide coating is less likely to take place.;This heat transfer tube is used in an LNG vaporizer equipped with an Al alloy panel unit including a panel composed of a plurality of heat transfer tubes arranged in a row in the form of a curtain, and a lower header and an upper header respectively connected to the panel at its lower end portion and its upper end port ion; wherein the LNG is vaporized by heat exchange between seawater flowing down along the surface of the panel from the upper end portion of the panel unit and the LNG flowing through theheattransfertubes. In this LNG vaporizer, the outer surface of the heat transfer tube at least in the lower end portion of the panel and the outer surface of the lower head are subjected to surface roughening by blasting, and then, a coating of an Al-Mg alloy containing Mg at a content in the range of 1 to 80% by mass, and having a thickness of 100 to 1000 µm was formed by thermal spraying to realize protection by sacrificial corrosion. Formation as the corrosion protective of an A1 alloy coating containing Zn and/or Mn at a content in the range of 0.3 to 3.0% by mass with the proviso that the content of (Zn + Mn) is in the range of 0.3 to 3.0% by mass and containing Mg at a content in the range of 0. 3 to 5% by mass is also effective.