The Damage Is Inside the Vessel, Where No One Looks Until Commissioning
A boiler looks indestructible, and its shell is. The vulnerability is internal and on the connections. The water and fire tubes, headers and drum internals are bare steel that corrodes the moment humid, salt-laden marine air circulates through the vessel, and that corrosion stays invisible until the boiler is opened at destination, sometimes after months in a yard. The machined faces, the nozzle flanges, manhole and handhole seats and instrument connections, are precision surfaces that must seal under pressure; a corroded or knocked flange face becomes a leak path the day the boiler is fired.
The proven defence is to make the vessel a sealed, dry micro-climate. BENZ drains and dries the boiler, then preserves the internals with VCI and desiccant and, where the OEM specifies it, holds the vessel under a low-pressure dry-air or nitrogen blanket so no oxygen-bearing moist air can reach the steel. Every opening is capped and blanked, nozzle and manway faces get fitted protectors over a film of rust preventive, and the shell is cradled on its design saddles and bolted to a heat-treated skid or steel base frame rated to its tonnage. Deck-cargo boilers receive additional heavy-duty weatherproof and, where needed, fiber-reinforced barrier wrapping against rain and sea spray.