Gas carrier calls Euroservices terminal on 25/07/2015 for cleaning corroded cargo tanks.
Liquid samples taken during propane discharge operations at previous unloading port indicated "3a" at the ASTM copper strip corrosion standard. As a result, there was a reasonable assumption that cargo tanks were contaminated by the off-spec propane cargo, resulting in corrosion.
After gasfreeing and bringing the tanks under breathable air, SGS-surveyor performed a visual inspection in Zeebrugge. A wall wash from the surface of the cargo tanks was taken in order to determin the level of corrosion. Analysis of the wall wash samples at the SGS Laboratory indicated level "4a" at the ASTM copper strip corrosion standard. As a result cargo tanks were found unsuitable for further trading in LPG. Hydro jet cleaning using suitable chemicals became inevitable.
In order to clean the entire surface of the cargo tanks with high pressure water, scaffolding became imperative.
During the cleaning operation SGS surveyor took wall wash samples at regular times to monitor the process. In the end, we reached our goal; "1a" at the ASTM copper strip corrosion standard.
After removal of the scaffolding, the cargo tanks were dried with our shore based hot air fans. Our fans produce 15000 cbm of hot air per hour. Hoses are inserted in the cargo tanks via the open tank lids. Once completely dry and accepted by surveyor, the cargo tanks were closed in order to start nitrogen purging from shore. Finally, the cargo tanks were gassed-up with propane using our shore vaporizer and our shore flare.
The vessel left Zeebrugge with perfectly cleaned cargo tanks under propane vapours, ready to load next cargo!
Similar cleaning operations have been performed many times at our terminal in the past from last cargoes ammonia and LPG. As a result we have gathered quite some expertise in cleaning contaminated/corroded cargo tanks of LPG carriers.