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IS 6476 : 1987Aluminium bulb plates for marine application

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ASTM B928/B928M - 21 · DNV-RU-SHIP Pt.2 Ch.2 · EN 755-2
CurrentSpecializedSpecificationBIMMaterials Science · Structural Engineering and Structural Sections
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OverviewValues6InternationalTablesFAQ4Related

IS 6476:1987 is the Indian Standard (BIS) for aluminium bulb plates for marine application. This standard specifies the dimensions, sectional properties, tolerances, and material requirements for wrought aluminium and aluminium alloy bulb plates. These sections are primarily intended for use as structural stiffeners in marine applications like shipbuilding due to their high strength-to-weight ratio and corrosion resistance.

Aluminium bulb plates for marine application

Overview

Status
Current
Usage level
Specialized
Domain
Materials Science — Structural Engineering and Structural Sections
Type
Specification
International equivalents
ASTM B928/B928M - 21 · ASTM International (USA)DNV-RU-SHIP Pt.2 Ch.2 · DNV (Det Norske Veritas), Norway/GermanyEN 755-2:2016 · CEN (European Committee for Standardization)ISO 6261:2005 · ISO (International Organization for Standardization)
Typically used with
IS 733IS 1608IS 504IS 1817
Also on InfraLens for IS 6476
6Key values4Tables4FAQs

BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.

Practical Notes
! The bulb at the edge of the plate significantly increases the section's bending stiffness and buckling resistance, making it more efficient than a simple flat bar for stiffening ship plating.
! Alloy N8 is commonly specified due to its excellent weldability and resistance to corrosion in saltwater environments, a critical factor for marine structures.
! Ensure dimensional tolerances, especially straightness (camber and sweep), are checked upon delivery as they are crucial for fitting and welding during hull construction.
Frequently referenced clauses
Cl. 3Chemical CompositionCl. 4Mechanical PropertiesCl. 5Dimensions and TolerancesCl. 6Freedom from Defects
Pulled from IS 6476:1987. Browse the full clause & table index below in Tables & Referenced Sections.
aluminiumaluminium alloybulb plates

International Equivalents

Similar International Standards
ASTM B928/B928M - 21ASTM International (USA)
HighCurrent
Standard Specification for High Magnesium Aluminum-Alloy Sheet and Plate for Marine Service and Similar Environments
Covers high-magnesium 5xxx series alloy plates (e.g., 5083) specifically for marine service, which is a key material in IS 6476.
DNV-RU-SHIP Pt.2 Ch.2DNV (Det Norske Veritas), Norway/Germany
HighCurrent
Rules for Classification: Ships - Part 2 Materials and welding - Chapter 2 Metallic materials
Details material requirements for aluminium alloys used in ship construction, including profiles, properties, and testing.
EN 755-2:2016CEN (European Committee for Standardization)
MediumCurrent
Aluminium and aluminium alloys - Extruded rod/bar, tube and profiles - Part 2: Mechanical properties
Specifies mechanical properties for extruded profiles, including alloys 6082 and 5083 used in IS 6476, but is not specific to bulb plates or marine use.
ISO 6261:2005ISO (International Organization for Standardization)
MediumCurrent
Wrought aluminium and aluminium alloys — Rolled products for marine applications (sheet, strip and plate)
Provides general specifications for rolled aluminium products for marine use, covering relevant alloys but not the specific bulb plate extruded shape.
Key Differences
≠IS 6476:1987 uses older Indian alloy designations (e.g., HE30, NE8), whereas modern international standards use the global 4-digit system (e.g., 6082, 5083).
≠Temper designations in IS 6476:1987 (e.g., 'WP' for solution treated and aged) are less detailed than the modern alphanumeric system used internationally (e.g., T6, T651, H111, H116).
≠International standards like DNV Rules or ASTM B928M mandate more rigorous testing regimes and stricter certification/traceability requirements (e.g., EN 10204 Type 3.1 or 3.2 certificates) than the 1987 Indian standard.
≠While IS 6476 includes 6xxx series alloys (HE30), modern international marine standards place a stronger emphasis on 5xxx series alloys (like 5083, 5086) for superior seawater corrosion resistance, especially for wetted surfaces.
Key Similarities
≈All standards specify requirements for the same fundamental families of alloys suitable for marine construction: heat-treatable Al-Mg-Si (6xxx series) and non-heat-treatable Al-Mg (5xxx series).
≈The primary objective across all standards is to ensure materials possess adequate strength, ductility, and corrosion resistance for structural applications in a marine environment.
≈Key mechanical properties like Tensile Strength, 0.2% Proof Stress (Yield Strength), and Elongation are mandatory specified parameters in both IS 6476 and its international counterparts.
≈All standards recognize the importance of manufacturing control by specifying permissible dimensional and geometric tolerances (e.g., for thickness, straightness, twist) crucial for fit-up and fabrication.
Parameter Comparison
ParameterIS ValueInternationalSource
Alloy Designation Equivalent (HE30)HE306082EN 573-3:2019
Alloy Designation Equivalent (NE8)NE85083ASTM B928/B928M - 21
Min. Tensile Strength (Rm) for HE30-WP / 6082-T6309 MPa (31.5 kgf/mm²)≥ 290 MPa (for extruded profiles ≤ 25mm thick)EN 755-2:2016
Min. 0.2% Proof Stress (Rp0.2) for HE30-WP / 6082-T6255 MPa (26.0 kgf/mm²)≥ 250 MPa (for extruded profiles ≤ 25mm thick)EN 755-2:2016
Min. Elongation (%) for HE30-WP / 6082-T68%≥ 8% (on A50mm gauge)EN 755-2:2016
Min. Tensile Strength (Rm) for NE8 / 5083-H111275 MPa (28.0 kgf/mm²)≥ 275 MPaASTM B928/B928M - 21
Min. 0.2% Proof Stress (Rp0.2) for NE8 / 5083-H111125 MPa (13.0 kgf/mm²)≥ 125 MPaASTM B928/B928M - 21
⚠ Verify details from original standards before use

Key Values6

Quick Reference Values
Specified alloy grade for marine useN8 (Aluminium-Magnesium alloy)
Min. Tensile Strength (Alloy N8)295 MPa
Min. 0.2% Proof Stress (Alloy N8)195 MPa
Min. Elongation on 5.65√S₀ gauge length (Alloy N8)12 %
Tolerance on depth (d <= 100mm)±1.5 mm
Tolerance on web thickness (t w <= 6mm)±0.50 mm

Tables & Referenced Sections

Key Tables
Table 1 - Chemical Composition of Wrought Aluminium Alloys
Table 2 - Mechanical Properties of Bulb Plates
Table 3 - Dimensions and Sectional Properties of Bulb Plates
Table 4 - Dimensional Tolerances for Bulb Plates
Key Clauses
Clause 3 - Chemical Composition
Clause 4 - Mechanical Properties
Clause 5 - Dimensions and Tolerances
Clause 6 - Freedom from Defects

Related Resources on InfraLens

Cross-Referenced Codes
IS 733:1983Wrought Aluminium and Aluminium Alloy Plate, ...
→
IS 1608:2005Mechanical Testing of Metals - Tensile Testin...
→
IS 504:2020Ceramic Glazed Tiles — Specification
→
IS 1817:2016Methods of Test for Coating Thickness on Non-...
→

Frequently Asked Questions4

What are the primary aluminium alloys specified in this standard?+
The standard specifies Aluminium-Magnesium alloys, particularly grade N8, which is suitable for marine environments (Clause 3.1, Table 1).
What is the main purpose of the 'bulb' on these plates?+
The bulb acts as an integral flange to increase the section's moment of inertia and resistance to bending and local buckling, making it an efficient stiffener (Clause 1.1).
What are the minimum mechanical properties for an N8 alloy bulb plate?+
For alloy N8, the minimum ultimate tensile strength is 295 MPa, the minimum 0.2% proof stress is 195 MPa, and the minimum elongation is 12% (Table 2).
What is the straightness tolerance for these bulb plates?+
The deviation from straightness (camber) should not exceed L/1000, where L is the length of the plate (Clause 5.4.1).

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