Wooden cross arms

IS 2203: Scope - Key Specifications & Tables

Scope:
IS 2203 covers specifications for wooden cross arms used in overhead power lines, detailing dimensions, materials, and quality requirements.

1. Dimensions of Wooden Cross Arms for 11 kV Lines (Clause 7.1.2)

Note: Holes accommodate fittings like insulators, clamps, and pins.

2. Maximum Permissible Size of Knots (Clause 5.3.5)

3. Selection of Timber Species (Clause 4.1 & Annex A)

IS 2203 Key References Summary

1. Dimensions of Wooden Cross Arms (Clause 7.1.2, Table 2)

2. Maximum Permissible Knot Sizes (Clause 5.3.5, Table 1)

IS 2203: Definitions & Key Specifications for Wooden Cross Arms

1. Dimensions of Wooden Cross Arms (Clause 7.1.2, Table 2)

2. Maximum Permissible Size of Knots (Clause 5.3.5, Table 1)

IS 2203: Material Selection & Timber Species for Wooden Cross Arms

Timber Classification by Modulus of Rupture (MoR) in Green Condition (>25% moisture) [Clause 4.1]

Key Specifications:

• MoR tested per IS 1708:1986 on small green specimens.
• Moisture content should be above 25% during testing.
• Selection based on strength class ensures durability and load-bearing capacity.
• Use IS 287:1973 for permissible moisture content limits.
• Preservation methods per IS 2203 and IS 1708 ensure longevity.

Summary:

• Choose timber species from Group A for highest strength applications.
• Groups B and C are suitable for moderate load conditions.
• Ensure timber meets moisture and preservation standards for service life.

graph TD
  A[Timber Species] -->|MoR ≥ 85| GroupA[Group A: Very Strong (Sal)]
  A -->|65 ≤ MoR < 85| GroupB[Group B: Strong (Teak)]
  A -->|45 ≤ MoR < 65| GroupC[Group C: Moderate (Chir)]

This classification guides engineers in selecting appropriate timber for cross arms per IS 2203.

IS 2203: Defects and Quality Requirements for Cross Arms

1. Prohibited Defects (Clause 5.2)

Cross arms must be free from:

• Cross breaks
• Reaction wood
• Decayed or unsound knots, knots > 50 mm diameter
• Splits extending top-to-bottom or side-to-side
• Pitch seams

2. Permissible Defects (Clause 5.3)

Certain defects are allowed within limits specified, especially knots.

3. Measurement Standard

Defects measured as per IS 3364 (Part 2): 1976.

4. Key Table: Maximum Permissible Size of Knots (Clause 5.3.5)

Summary:

• No large or decayed knots (>50 mm) allowed.
• Smaller knots allowed but limited in size and distribution.
• Defect measurement per IS 3364 ensures uniform quality.

This ensures structural integrity and durability of wooden cross arms in transmission lines.

IS 2203: Manufacturing Details & Finishing of Wooden Cross Arms

1. Dimensions of Wooden Cross Arms (Clause 7.1.2, Table 2)

2. Permissible Defects - Maximum Knot Sizes (Clause 5.3.5, Table 1)

IS 2203 - Dimensions and Tolerances for Wooden Cross Arms

Key Points from IS 2203:

• Clause 6.2: Cross arms must have bevelled corners on the best edge to distinguish upper and lower halves.

• Clause 7.1.1: Cross arm dimensions and drilling details must match purchaser's drawings.

• Clause 7.1.2 (Table 2): Dimensions for 11 kV Wooden Cross Arms

• Clause 5.3.5 (Table 1): Maximum Knot Sizes

| Knot Location | Max Single Knot Diameter (mm) | Sum of Knot Diameters (mm

IS 2203: Preservative Treatment of Wooden Cross Arms

Key Specifications:

• Clause 8.1:

  • All cross arms made from non-durable species and sapwood of durable species must be preservative treated as per IS 401:1982 (same as wood poles).

• Clause 8.2 (Preliminary Treatment):

  • Untreated cross arms must receive prophylactic treatment promptly to prevent insect/fungal damage (per IS 401:1982).
  • Cross arms (treated or untreated) should be stacked on creosoted or treated crossers, at least 150 mm above ground for air circulation and decay prevention.

Marking Requirements (Clause 11.1):

Each cross arm must be clearly marked with:

• Group of wooden cross arm
• Timber species symbol (see Annex A)
• Year of manufacture
• Source of manufacture
• Year of preservative treatment

Reference: IS 401:1982 Treatment Summary (Typical)

Visual: Cross Arm Stacking for Treatment

graph LR
A[Ground] --> B[Treated Crossers (creosoted)]
B --> C[Cross Arms stacked 150 mm above ground]
C --> D[Good air circulation]
C --> E[Protection from decay agents]

Summary: Use IS 401:1982 for preservative treatment methods; stack cross arms properly; mark all treated arms as per IS 2203 Clause 11.1.

IS 2203: Storage and Handling of Wooden Cross Arms

Key Specifications & Tables (Clause 7.1.2, Table 2)

Storage & Handling (Clause 8.2)

• Preliminary Treatment: Untreated cross arms must receive prophylactic treatment per IS 401:1982 to prevent insect/fungal damage.
• Stacking: Cross arms (treated or untreated) must be stacked on creosoted or treated sleepers, 150 mm above ground for air circulation and protection against decay.
• Dimensional Tolerance: ±5 mm for external dimensions, ±2 mm for holes/slots

IS 2203: Testing and Inspection Key Points

1. Defects Measurement (Clause 5.1)

• Defects are classified as prohibited and permissible (Clauses 5.2 & 5.3).
• Measurement of defects follows IS 3364 (Part 2): 1976.

2. Maximum Permissible Size of Knots (Clause 5.3.5, Table 1)

3. Dimensions of Wooden Cross Arms for 11 kV Lines (Clause 7.1.2, Table 2)

IS 2203: Marking & Identification of Wooden Cross Arms

Key Specifications (Clause 11.1)

Each wooden cross arm must be marked legibly and indelibly with:

• Group of wooden cross arm
• Species of timber symbol (see Annex A)
• Year of manufacture
• Source of manufacture
• Year of preservative treatment

Species Symbols (Annex A)

(Refer Annex A for full list)

Maximum Permissible Knot Sizes (Clause 5.3.5, Table 1)

Cross Arm Hole Dimensions (Clause 7.1.2, Table 2)