Each scrubber in this tanker inert gas system is fabricated in Ferralium® 255 alloy plate, chosen for its excellent corrosion resistance and high mechanical strength in a highly corrosive duty. Ferralium® 255 is a super duplex stainless steel, and that strength also suits it to the inert gas fan impellers, where high peripheral speeds are normal.
Why an inert gas system
Static electricity discharge is thought to be one cause of past tanker explosions, generated by high-pressure seawater jets cleaning empty tanks in the presence of air and residual oil vapour. Inert gas systems remove that risk by replacing normal air, and its oxygen content, so the conditions for ignition are never present. They are now installed in new tankers and retrofitted to older ships already in service.
How the scrubber works
The system cleans boiler smoke or diesel exhaust gas before the cold inert gas is blown into the holds: scrubbing, cooling, filtering (or dusting-off), chemically neutralising and demisting. In the scrubber, the main part of the system, the gas is sprayed and saturated with seawater, almost completely cleansed of sulphur, and finally dusted off by filtering down to less than a micron. The resulting liquid contains sulphurous and sulphuric acids heavily contaminated with chlorides, which can present a serious corrosion problem.
The build
The scrubber shown is one of three built by Societe Francaise d'Aerodynamique et de Thermodynamique (SOFRAIR), 1 Avenue de Chatou, F 92508 Rueil-Malmaison, France, for inert gas systems in three new tankers. It is approximately 43 1/2" in diameter and 157" in height.
