Code of practice for maintenance of wood poles for overhead power and telecommunication lines

IS 6711: Scope - Key Points & Specifications

Scope:
IS 6711 covers specifications for wood poles used in overhead power and telecommunication lines, focusing on quality, inspection, and treatment.

Key Specifications & References:

• Rounding Off:
  Final test/analysis values must be rounded per IS 2-1960, retaining the same significant figures as the specified values.

• Terminology:
  Definitions from IS 707-1968 apply for wood poles.

• Inspection Details (Clause 4.1):
  Inspection reports must record:

  • Location, supplier, preservative treatment & absorption
  • Pole dimensions (length, diameter at ground & top)
  • Initial defects and biological attacks (termite/fungus) with severity codes:

    Code	Description	% Attack
    Sw/Sf	Slight termite/fungus	5-10%
    Mw/Mf	Moderate termite/fungus	10-25%
    Bw/Bf	Bad termite/fungus	25-50%
    Dw/Df	Destroyed by termites/fungus	>50%
    R	Recommended for rejection	Immediate

• Related IS Codes:

  • IS 876-1970: Wood poles for overhead lines
  • IS 5978-1970: Design code for wood poles
  • IS 2203-1962: Wooden cross arms

Summary Table: Biological Attack Severity

This scope ensures wood poles meet durability, dimensional, and treatment standards for safe overhead line use.

IS 6711 - Definitions (Clause 2.1)

• Reference: Definitions and terms are as per IS 707:1968 (Wood and Wood Products).
• The standard defers to IS 707 for terminology related to wood poles.

Key Points on Inspection (Clause 0.7 & 4.1)

• Rounding Off: Final test values must be rounded per IS 2:1960 with the same significant figures as specified.
• Inspection Report Details (Clause 4.1, Appendix A):
  Includes:
  • Locality, supplier, preservative treatment, absorption, treatment process.
  • Pole dimensions at installation (length, diameter at ground and top).
  • Initial defects and biological attacks (termite/fungus severity codes).
  • Dates of installation and inspection, inspection type.
  • Remedial measures recommended and carried out.

Biological Attack Legend (Severity of Damage)

Summary Table: Inspection Report Parameters

This concise framework ensures uniform understanding and assessment of wood poles per IS 6711 and related standards.

IS 6711 - Inspection of Wood Poles: Key Points & Specifications

Types of Inspection (Clause 3.1, 7.5)

• Routine Inspection

  • Excavate soil 7.5 to 15 cm deep, 10 to 15 cm wide around pole.
  • Sound pole with hammer from bottom to reachable height.
  • Detect softening (rot) and measure depth with increment borer if needed.

• Detailed Inspection

  • Excavate soil 40 to 60 cm deep, 25 cm wide.
  • Sound entire pole surface, especially near cracks, knots, bolt holes.
  • Use increment borer to measure rot depth.
  • Plug borer holes with treated wood dowels immediately.

Inspection Report (Appendix A)

Include:

• Locality, supplier, preservative treatment, absorption, treatment process.
• Pole dimensions: total length, diameter at ground and top.
• Initial defects and their positions.
• Dates of installation and inspection.
• Type of inspection (routine/detailed).
• Biological attack legend (termite/fungus severity).
• Remedial measures recommended and carried out.
• Inspector's initials.

Biological Attack Legend

Summary Table: Excavation for Inspection

This ensures timely detection of decay and structural integrity assessment of wood poles as per IS 6711.

IS 6711: Inspection Procedures for Wooden Poles

Types of Inspection (Clause 3.1 & 7.5)

1. Routine Inspection:

   • Excavate soil 7.5 to 15 cm deep and 10 to 15 cm wide around the pole base.
   • Sound the pole all around with a hammer from the excavation bottom upwards.
   • Detect softening (rot) by hammer sound.
   • Use an increment borer to measure rot depth if needed.

2. Detailed Inspection:

   • Excavate soil 40 to 60 cm deep and 25 cm wide around the pole.
   • Sound the entire pole surface with a light hammer, focusing on cracks, knots, bolt holes.
   • Measure rot depth with an increment borer.
   • Plug borer holes immediately with treated wood dowels.

Rounding Off Values (Clause 0.7)

• Follow IS:2-1960 for rounding numerical results.
• Retain the same number of significant figures as the specified value.

Summary Table: Excavation Dimensions for Inspection

flowchart TD
    A[Start Inspection] --> B{Type of Inspection?}
    B -->|Routine| C[Excavate 7.5-15 cm deep, 10-15 cm wide]
    B -->|Detailed| D[Excavate 40-60 cm deep, 25 cm wide]
    C --> E[Sound pole with hammer]
    D --> F[Sound entire pole surface]
    E --> G{Softening detected?}
    F --> G
    G -->|Yes| H[Measure rot depth with increment borer]
    G -->|No| I[No rot detected]
    H --> J[Plug holes with treated wood dowels]
    I --> K[Inspection complete]
    J --> K

This ensures thorough assessment of pole integrity per IS 6711 standards.

IS 6711: Remedial Treatment for Biological Damage

Key Preservatives (Table 1 - Clause 5.1.1.1)

Refer IS:401-1967 for preservative composition and preparation.

Treatment Procedure (Clause 5.1.1.7)

• Apply two liberal brush coats of:
  • Hot creosote OR
  • 5% solution of pentachlorophenol in petroleum solvent
• Coverage: From top to 40-60 cm below ground level
• Frequency: Initially after 12 years of installation, then at every detailed inspection
• Ensure preservative penetrates holes, crevices, and damaged areas thoroughly.

Important Notes

• Only poles not rejected for excessive damage should receive remedial treatment (Clause 5.1).
• Maintain a detailed inspection report as per Appendix A (Clause 4.1).

flowchart TD
    A[Inspection of Pole] --> B{Condition}
    B -->|Excessive Damage| C[Reject Pole]
    B -->|Minor Damage| D[Remedial Treatment]
    D --> E[Apply Preservative]
    E --> F[Two Brush Coats Hot Creosote / 5% Pentachlorophenol]
    F --> G[Penetrate Holes & Crevices]
    G --> H[Record in Inspection Report]

This ensures enhanced service life and protection from biological deterioration.

IS 6711: Remedial Treatment for Mechanical Damages

Key Points from IS 6711:

• Clause 5.1:
  Remedial treatment applies only to poles not rejected due to excessive rot, insect attack, or mechanical damage.

• Treatment Method:
  Follow the procedure in Clause 5.1.1 (which covers biological damage treatment).

• Preservatives (Table 1):

• Additional Treatment (Clause 5.1.1.7):
  Apply two liberal brush coats of hot creosote or 5% pentachlorophenol solution in petroleum solvent, from top to 40-60 cm below ground level.
  • Initial treatment after 12 years of installation
  • Repeat with every detailed inspection
  • Ensure full penetration into holes and crevices

Summary for Mechanical Damage:

• Inspect poles thoroughly; reject if damage is excessive.
• For repairable poles, use the same preservatives and application methods as for biological damage.
• Ensure proper penetration and repeat treatments per inspection schedule.

Reference:

• For preservative composition & preparation, see IS 401-1967 (Code of practice for timber preservatives).

flowchart TD
    A[Inspection of Pole] --> B{Damage?}
    B -->|Excessive| C[Reject Pole]
    B -->|Repairable| D[Apply Remedial Treatment]
    D --> E[Use Preservatives from Table 1]
    E --> F[Apply 2 coats hot creosote or 5% pentachlorophenol]
    F --> G[Ensure penetration in crevices]
    G --> H[Repeat treatment every inspection]

This approach ensures prolonged service life of poles with mechanical damages by combining inspection, selective rejection, and preservative treatment.

Pole Replacement Criteria (IS 6711: Clause 6.3 & related)

• Replacement Trigger:
  Replace pole if:

  • Damage due to decay/defects exceeds safe limits.
  • Any permissible defect grows to 2.5 times its original size.

• New Pole Installation:

  • Erect new treated solid or jointed wood pole.
  • Position at 1 m away from original pole location.

Inspection Procedures (Clause 7.5):

Pole Top Treatment (Clause 5.1.1.6):

• Remove soft/rot portions by scraping.
• Brush coat top 3 m (or affected portion below 3 m) with 5% pentachlorophenol solution in petroleum solvent.
• Fill scooped-out tops with paste of 5% pentachlorophenol + fly ash; cover suitably.

flowchart TD
    A[Inspect Pole] --> B{Defect > Safe Limit or Defect > 2.5x original?}
    B -- Yes --> C[Remove soil 40-60 cm deep, 25 cm wide]
    C --> D[Sound pole with hammer]
    D --> E[Use increment borer if rot suspected]
    E --> F[Replace pole with treated wood pole]
    F --> G[Install new pole 1 m away]
    B -- No --> H[Routine inspection with 7.5-15 cm excavation]
    H --> I[Sound pole, monitor defects]
    I --> A

Summary:
Replace poles when defects enlarge beyond 2.5 times original size or unsafe decay is found. Inspect routinely by excavation and hammer sounding, use preservative treatment on top portions showing rot.

IS 6711: Maintenance of Jointed Wood Poles — Key Points

• Replacement Criteria (Clause 6.3):

  • Replace pole if decay/defects exceed safe limits.
  • If any defect grows to 2.5 times original size, replacement is mandatory.
  • New pole must be installed 1 m away from the original position.

• Preservation:

  • Use treated solid or jointed wood poles only.
  • Follow the Code of Practice for Preservation of Timber (Second Revision) for treatment methods.

• Typical Defect Limits:

  • Decay or cracks should not reduce the cross-section below the safe structural capacity.
  • If the defect compromises strength, pole must be replaced.

Important Specification Summary

Maintenance Checklist

• Inspect poles periodically for decay, cracks, or splits.
• Measure defects; compare with original sizes.
• Treat poles as per preservation code.
• Replace poles exceeding defect limits.

flowchart TD
    A[Inspect Pole] --> B{Defect Size > 2.5× original?}
    B -- Yes --> C[Replace Pole 1m away]
    B -- No --> D{Decay beyond safe limit?}
    D -- Yes --> C
    D -- No --> E[Continue Maintenance]

This ensures structural safety and longevity of jointed wood poles in overhead lines.

IS 6711: Documentation and Reporting (Clause 4.1 & Appendix A)

After inspection of wood poles, a detailed report must be prepared and retained throughout the pole's service life. The report format is specified in Appendix A and includes:

Legend for Biological Attack Severity:

Rounding off values in reports should follow IS:2-1960 for consistency.

flowchart TD
   

IS 6711 - Inspection Report Format for Wood Poles

Key Specifications (Clause 4.1 & Appendix A):

The inspection report must include:

• Locality of installation
• Supplier (origin)
• Preservative treatment given and absorption
• Treatment process
• Dimensions at installation:
  • Total length
  • Diameter at ground level
  • Top diameter
• Initial defects and their positions
• Dates:
  • Installation
  • Inspection
• Type of inspection: Routine or detailed
• Biological attack details (with legend codes for severity)
• Diameter at ground level (current)
• Other observations
• Inspector's initials
• Recommended remedial measures and status of implementation

Legend for Biological Attack Severity:

Summary Diagram of Inspection Report Structure:

graph TD
    A[Inspection Report] --> B[Installation Details]
    A --> C[Preservative Treatment]
    A --> D[Dimensions]
    A --> E[Defects & Biological Attack]
    A --> F[Dates & Inspection Type]
    A --> G[Observations & Recommendations]
    B --> B1[Locality]
    B --> B2[Supplier]
    C --> C1[Treatment Given]
    C --> C2[Absorption]
    D --> D1[Length]
    D --> D2[Diameter Ground Level]
    D --> D3[Top Diameter]
    E --> E1[Initial Defects]
    E --> E2[Biological Attack Legend]