Tank-top doubler

A tank-top doubler is a reinforcing plate welded onto the inner bottom (tank-top) plating to spread a concentrated load from a foundation or pillar into the double-bottom structure below. It is fitted under machinery seats, deck-cargo or container pedestal footings, and crane or pillar bases where the point load would over-stress the plating or cause local buckling. The doubler increases the local plate thickness and is sized so the load passes into a girder or floor beneath rather than punching the plate. Class surveyors check doublers for edge welds, corrosion in the trapped crevice, and adequate continuity into the supporting structure.