Aluminium channels

IS 3921 Scope & Key Specifications for Aluminium Channels

Scope (Clause 2.0)

• Defines aluminium channels covered by this standard.
• Applies to standard dimensions, sectional properties, and marking of aluminium channels used in structural applications.

Key Specifications (Clause 6.1 & Table 1)

• Aluminium channel designations (e.g., ALC 40x20-0.44) specify:
  • Mass per metre (kg/m)
  • Sectional area (cm²)
  • Depth (h) and width (b) of section (mm)
  • Thickness of web (tw) and flange (tf) (mm)
  • Radius at root (mm)
  • Centre of gravity (Cy, cm)
  • Moment of inertia (Ix, Iy, cm⁴)
  • Radius of gyration (Tx, Ty, cm)
  • Modulus of section (Zx, Zy, cm³)

Dimensional Tolerances (Clause 6.2)

• As per IS 3965-1981 for aluminium sections.

Rounding Off (Clause 0.7)

• Final test/calculation results rounded per IS 2-1960, matching significant figures of specified values.

Example Table Extract (ALC 40x20-0.44)

This standard provides comprehensive sectional data for aluminium channels to aid design and quality control.

IS 3921 - Definitions and Symbols (Clauses 2.0, 3.1, 6.1)

Key Letter Symbols:

Important Formulas:

• Section Modulus: [ Z_x = \frac{I_x}{C_x}, \quad Z_y = \frac{I_y}{C_y} ]
• Radius of Gyration: [ r_x = \sqrt{\frac{I_x}{a}}, \quad r_y = \sqrt{\frac{I_y}{a}} ]

Table 1 Summary (Excerpt for Aluminium Channels):

IS 3921: Materials & Alloys for Aluminium Structural Sections

1. Alloys & Temper (Clause 5.1.1)

• Aluminium alloys must conform to IS: 733-1983.
• Common alloys used: 19000, 24345, 24534, 52000, 53000, 63400, 64423, 64430, 65032, 74530.
• Temper conditions as per IS: 733 for suitable strength and ductility.

2. Key Dimensions & Sectional Properties (Clause 6.1, Table 1)

• Sections are defined by Designation, Mass per meter, Sectional Area, Depth (h), Width (b), Thickness (tw, tf), Radius at root (r), Centre of Gravity (Cy), Moment of Inertia (Ix, Iy), Radius of Gyration (Tx, Ty), and Section Modulus (Zx, Zy).

3. Example from Table 1: Aluminium Channel ALC 50x30-1.14

• Mass = 1.14 kg/m
• Area = 4.23 cm²
• Depth (h) = 50 mm
• Width (b) = 30 mm
• Thickness web/flange = 4 mm
• Radius at root = 6 mm
• Ix = 15.80 cm⁴, Iy = 3.52 cm⁴
• Zx = 6.32 cm³, Zy = 1.72 cm³

Summary:

• Use IS: 733-1983 alloys listed above.
• Select aluminium sections

IS 3921 - Aluminium Channels: Dimensions & Sectional Properties

Key Points from Clause 6 (Table 1 Summary)

Typical Dimensions & Properties Example (ALC 60x30-1.55)

Additional Notes:

• Dimensional tolerances are per IS 3965-1981.
• Aluminium alloys conform to IS 733-1983.
• Use sectional properties for structural analysis (bending, shear,

IS 3921 - Manufacturing Requirements for Aluminium Channels

Key Points from Clause 6.1.1 & Table 1:

• Sections other than those in Table 1 can be manufactured by mutual agreement.
• Aluminium alloys and tempers must comply with IS 733-1983 (Clause 5.1.1).
• Table 1 provides detailed sectional properties for standard aluminium channels.

Important Specifications from Table 1:

Example (ALC 50x30-1.14):

• Mass/m: 1.14 kg
• Area: 4.23 cm²
• Depth: 50 mm
• Width: 30 mm
• Thickness: Web and flange 4 mm
• Radius at root: 6 mm
• Ix: 15.80 cm⁴, Iy: 3.52 cm⁴
• Zx: 6.32 cm³, Zy: 1.72 cm³

Summary:

• Use Table 1 for standard dimensions and properties.
• Custom sizes allowed with purchaser-manufacturer agreement.
• Follow alloy and temper standards per IS 733-1983.
• Sectional properties support design calculations for strength and stability.

flowchart TD
    A[Start: Select Aluminium Channel] --> B{Standard Section?}
    B -- Yes -->

IS 3921: Marking and Packaging of Aluminium Channels

Clause 8.1 - Marking Requirements:

• Channels must be clearly marked with:
  • Designation
  • Alloy and temper
  • Manufacturer's name
  • Lot number/year of manufacture

Clause 8.2 - ISI Certification Mark:

• Channels may carry the ISI Certification Mark.
• Use governed by Indian Standards Institution (Certification Marks) Act.
• ISI mark assures compliance with IS 3921 under strict inspection and quality control.

Key Specifications from Table 1 (Clause 6.1)

Example: Aluminium Channel ALC 100x50-4.09

IS 3921: Quality Control and Testing - Key Points

1. Rounding Off Test Results (Clause 0.7)

• Final test values must be rounded as per IS 2:1960.
• Number of significant digits in the result should match that of the specified value.

2. Marking and Identification (Clause 2.7 & 6.1)

• Aluminium channels are marked based on a density of 2.7 g/cm³.
• Table 1 provides detailed sectional properties for standard aluminium channels including:
  • Mass per metre (kg/m)
  • Sectional area (cm²)
  • Depth (h), Width (b), Thickness (tw, tf) in mm
  • Radius at root (mm)
  • Centre of gravity (cm)
  • Moment of inertia (Ix, Iy in cm⁴)
  • Radius of gyration (Tx, Ty in cm)
  • Modulus of section (Zx, Zy in cm³)

3. Testing and Compliance

• Testing methods should confirm adherence to the dimensional and mechanical properties listed.
• Use the sectional properties from Table 1 for structural design and verification.

Example Table Extract (Aluminium Channel ALC 50x30-1.14)

Summary Diagram of Sectional Properties

flowchart LR
    A[Aluminium Channel Section] --> B

Use of ISI Certification Mark per IS 3921

Clause 8.2 Summary:

• Channels (wrought aluminium and aluminium alloy sections) may be marked with the ISI Certification Mark.
• The ISI mark certifies compliance with the Indian Standard under a strict system of:
  • Inspection
  • Testing
  • Quality control supervised by ISI
• Continuous conformity checks by ISI ensure product reliability.
• Licensing for ISI mark use is governed by the Indian Standards Institution (Certification Marks) Act.
• Manufacturers/processors must obtain a license from ISI to use the mark legally.

Key Points on ISI Mark Usage

Additional Notes

• ISI mark indicates product quality and standard conformity.
• Manufacturers must maintain a quality control system approved by ISI.
• ISI conducts random checks on marked products to ensure ongoing compliance.

flowchart LR
    A[Manufacturer] --> B{Apply for ISI License}
    B -->|Approved| C[Produce ISI Marked Products]
    C --> D[Continuous ISI Inspection & Testing]
    D -->|Compliant| E[Market Products with ISI Mark]
    D -->|Non-compliant| F[License Revoked / Penalty]

For detailed licensing conditions, contact ISI regional offices listed in the standard or visit the ISI website.

Rounding Off Numerical Values as per IS 3921

• Standard Reference: IS 2-1960 governs rounding off rules.
• Rule: Final test or calculated values must be rounded off to the same number of significant places as specified in the standard.
• This ensures uniformity and compliance in reporting.

Summary of Rounding Off Rules (IS 2-1960):

• Retain the number of decimal places or significant figures as per the specified value.
• Example: If specified value = 3.55 (2 decimal places), round off 3.546 as 3.55, 3.544 as 3.54.

Additional Notes from IS 3921:

• Dimensional tolerances for aluminium sections follow IS 3965-1981.
• Refer to TABLE 1 in IS 3921 for sectional properties of aluminium channels with values rounded as per these rules.

flowchart TD
    A[Observed/Calculated Value] --> B{Number of Significant Figures?}
    B -->|Match Specified| C[Round off as per IS 2-1960]
    C --> D[Final Rounded Value]
    D --> E[Compliance Check]

In brief: Always round off final values to the same significant figures as the specified standard value, following IS 2-1960 rules for consistent compliance.

IS 3921: Key Formulas, Tables & Specifications for Aluminium Channels

Table 1: Indian Standard Aluminium Channels

• Provides dimensions, mass, and sectional properties for various aluminium channel designations (e.g., ALC 40x20-0.44).
• Properties include:
  • Mass per metre (kg/m)
  • Sectional area (cm²)
  • Depth (h), Width (b), Thickness of web (tw) and flange (tf) (mm)
  • Radius at root (mm)
  • Centre of gravity (Cy, cm)
  • Moments of inertia (Ix, Iy, cm⁴)
  • Radius of gyration (rx, ry, cm)
  • Modulus of section (Zx, Zy, cm³)

Important Letter Symbols (Clause 3.1):

Notes:

• Mass per metre is based on aluminium density = 2.7 g/cm³ (Clause 2.7).
• Use Table 1 for design and analysis referencing sectional properties directly.

Example Extract (from Table 1):