Aluminium bulb plates for marine application
1987 Edition

IS 6476 identifies aluminium-magnesium alloys suitable for marine bulb plates, emphasizing corrosion resistance and mechanical strength in marine conditions. Preferred alloys include grades such as Aluminium 5083 and 5052, known for their excellent weldability and durability in seawater environments. These alloys typically contain a magnesium content of around 4-5% to enhance corrosion resistance. The standard also specifies mechanical properties and surface finish requirements to ensure long-lasting performance in marine applications.

The standard classifies aluminium bulb plates into two main categories: those without welding flanges (designated as AMB) and those with welding flanges (designated as AMBW). Standard depths commonly range from 50 mm to 150 mm, with widths, flange thicknesses, and bulb radii adjusted according to the depth to maintain structural efficiency. Sectional properties provided include cross-sectional area, moment of inertia about principal axes, section modulus for bending design, and radius of gyration for stability assessments. Detailed tabulations of these parameters are available in the annexes of IS 6476.

Yes, IS 6476 explicitly includes specifications for aluminium bulb plates equipped with welding flanges. Clause 5.2 and Table 2 of the standard provide detailed dimensions and mass data for these profiles. In contrast, bulb plates without welding flanges are covered under Clause 5.1 and Table 1. The maximum permitted edge radius for these sections is 0.8 mm, ensuring appropriate fit and performance in marine structural assemblies.

Corrosion resistance in IS 6476 is achieved through the selection of appropriate aluminium alloys that naturally form a protective oxide layer, such as aluminium-magnesium alloys suited for marine environments. The standard mandates proper surface treatments and dimensional controls to enhance durability against saltwater exposure. Additionally, strict quality assurance measures ensure the absence of defects that could compromise corrosion resistance, thereby guaranteeing sustained performance of the bulb plates in harsh marine conditions.

IS 6476 recommends adherence to dimensional tolerances as specified in IS 3965-1981, ensuring allowable deviations to maintain interchangeability and proper fit. Test results and calculations must be rounded in accordance with IS 2-1960 to maintain consistency in reporting. Quality control practices include dimensional inspections, verification of chemical and mechanical properties, surface finish evaluations, and documentation for traceability. The standard also references ISO 1175-1986 for marine aluminium sections, aligning manufacturing processes with international best practices.