Cygnus thickness gauges detecting scrubber corrosion
23/11/2020
Exhaust gas cleaning systems (EGCSs), more commonly known as ‘scrubbers’, are currently being installed on thousands of vessels worldwide in order to comply with the IMO 2020 Sulphur Cap. As a recent innovation within the maritime industry, they have not been without some early issues, including EGCS corrosion. The wash water from scrubbers, containing the pollutants it has filtered, is acidic and therefore highly corrosive. The effect of the acidic nature of the corrosive scrubber wash water on the integrity of the ship is further aggravated by the high temperatures of exhaust gases. It is now firmly established that the structural integrity of the scrubber and associated pipework (for example SOx scrubber discharge water line) need to be regularly checked for signs of corrosion.Ultrasonic thickness gauging is a simple, inexpensive and reliable method to engage proactively with a schedule of preventative maintenance on scrubbers. Already, many companies around the world are choosing to use Cygnus thickness gauges on their vessels as part of routine scrubber structural integrity checks. Areas of particular interest and concern for vessels are the scrubber discharge outlet and the overboard pipe.
Cygnus Instruments was born into the marine industry; the company’s first gauges were designed 40 years ago specifically for hull inspection work. As a result, its MK5 units are all purpose-designed for a tough life on board a ship: they are waterproof (to IP67), drop proof and shock proof (to US MIL STD 810G standard). Readings taken can be logged and uploaded to simple software in order to be referred to later; thus, wall thinning and corrosion can be easily monitored over time and any issues can be caught and addressed at an early stage.
In addition, the Cygnus range of gauges all read through coatings of up to 20 mm thickness, which means there is no need to remove any of the important (and expensive) protective coatings or epoxy that safeguard against external scrubber corrosion. For heavily corroded metals where there is a thin or no coating left, Cygnus Plus gauges incorporating echo-echo and single-echo measuring modes coupled with the Measurement Stability Indicator (MSI™) can give the quick and reliable readings needed.
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