Method of test for the efficacy of preservatives and evaluating the natural durability of timbers used in cooling towers

IS 6497: Scope - Key Specifications & Tables

1. Specimen Sizes (Clause 4.1)

• Thin Specimen:

  • Size: 100 mm × 25 mm × 6 mm
  • Holes: 2 holes, 2 mm diameter
  • Used for flooded and extremely moist areas of towers
  • See Fig. 1 for brass nail positions

• Stake Specimen:

  • Size: 450 mm × 100 mm × 75 mm
  • Holes: 2 holes, 4 mm diameter
  • Used for alternate drying/wetting regions or structural members
  • See Fig. 2 for brass nail positions

2. Testing Method (Clause 5.1.1)

• Durability Evaluation:
  • Thin specimens: Weight loss method
  • Stakes: Rating method

3. Specimen Arrangement (Clause 4.4.1)

• 18 replicas per species and absorption level + 18 control specimens
• Mounted on wooden frame (Fig. 3)
• Reference species: Chir (Pinus roxburghii)

Summary Table of Specimen Dimensions

Notes:

• Specimens must conform to IS 2372:1963 for timber quality.
• Brass nails are used for fixing specimens (positions shown in figures).
• Testing ensures durability and efficacy of preservatives in cooling towers.

flowchart TD
    A[Select Timber Specimen] --> B{Specimen Type}
    B -->|Thin| C[100×25×6 mm, 2mm holes]
    B -->|Stake| D[450×100×75 mm, 4mm holes]
    C --> E[Install in flooded/moist areas]
    D --> F[Install in wet/dry

IS 6497: Referenced Standards & Key Specifications

Referenced Indian Standards (Clause 2.1):

• IS 401:1982 — Code of Practice for Preservation of Timber (3rd Revision)
• IS 2372:1963 — Specification for Timber for Cooling Towers

Specimen Sizes for Testing (Clause 4.1)

• Holes are for brass nail installation.
• Figures 1 & 2 in the standard illustrate specimen details.

Durability Evaluation (Clause 5.1.1)

• Methods: Weight loss and rating methods.
• Used for assessing preservative efficacy on thin specimens and stakes.

Notes on BIS and Standard Mark

• BIS governs quality control and licensing under the Bureau of Indian Standards Act, 1986.
• Standard Mark assures compliance and continuous quality checks.
• Indian Standards are periodically reviewed and amended.

If you need detailed tables on natural durability or preservative efficacy, refer to IS 401 and IS 2372 for comprehensive data.

flowchart TD
    A[IS 6497] --> B[IS 401:1982 Preservation]
    A --> C[IS 2372:1963 Timber Specs]
    B --> D[Preservative Efficacy Testing]
    C --> E[Specimen Size & Selection]
    D --> F[Weight Loss Method]
    D --> G[Rating Method]

This summarizes the key referenced standards and specimen specifications from IS 6497.

IS 6497 - Principle & Key Specifications Summary

• Specimen Sizes (Clause 4.1):

  • Thin specimen: 100 mm × 25 mm × 6 mm, with 2 holes of 2 mm dia (for flooded/moist areas).
  • Stake specimen: 450 mm × 100 mm × 75 mm, with 2 holes of 4 mm dia (for alternate wet/dry regions).

• Material: Timber must conform to IS 2372:1963 (Specification for timber for cooling towers).

• Durability Evaluation (Clause 5.1.1):

  • Thin specimens: Weight loss method.
  • Stakes: Rating method.

• Related Standards:

  • IS 401:1982 – Code of practice for preservation of timber.
  • IS 2372:1963 – Timber specification.

Specimen Details (Fig. 1 & 2 Summary)

Durability Evaluation Methods

flowchart LR
    A[Timber Specimen Selection] --> B{Area of Installation}
    B -->|Flooded/Moist| C[Thin Specimen 100x25x6 mm]
    B -->|Alternate Wet/Dry| D[Stake 450x100x75 mm]
    C --> E[Weight Loss Method]
    D --> F[Rating Method]

Note: Use IS 401 for preservation methods and IS 2372 for timber quality compliance.

IS 6497: Efficacy of Preservatives in Timber for Cooling Towers

Key Points from IS 6497:

• Test Methods:

  • Weight Loss Method: Used for thin specimens with high surface-to-volume ratio to accelerate preservative depletion.
  • Rating Method: Used for stakes (larger specimens) to evaluate deterioration visually.

• Specimen Size:

  • Thin specimens are sized to maximize surface area for rapid preservative leaching.

• Preservative Levels:

  • Testing involves 3 levels of preservative absorption.
  • Copper-Chrome-Arsenic (CCA) is the reference preservative.

• Scope:

  • Applies to timbers in cooling towers without heavy deposits from circulating water.

Typical Evaluation Procedure:

Visual Rating Scale (Example):

Summary:

• Weight loss % indicates preservative leaching.
• Visual ratings assess decay severity.
• CCA preservative sets benchmark performance.
• Testing at multiple absorption levels ensures reliability.

flowchart TD
    A[Prepare Specimens] --> B[Treat with Preservatives]
    B --> C[Expose to Environment]
    C --> D{Specimen Type}
    D -->|Thin| E[Measure Weight Loss %]
    D -->|Stake| F[Visual Rating]
    E --> G[Analyze Efficacy]
    F --> G

This method ensures reliable evaluation of preservative performance per IS 6497.

IS 6497 — Size and Selection of Timber Specimens

Specimen Sizes (Clause 4.1)

Number of Specimens (Clauses 4.4.1 & 5.1)

• Thin specimens: 18 replicas per species per absorption level + 18 control specimens.
• Stakes: 4 replicas per cooling tower.
• Specimens must be heartwood.
• Inspection at 1, 3, and 5 years (or 1, 2, 3 years if rapid deterioration).

Evaluation Methods (Clause 4.7.1)

• Thin specimens: Weight loss measurement.
• Stakes: Rating method based on visual deterioration.

Summary Table

flowchart LR
    A[Timber Specimens] --> B[Thin Specimens]
    A --> C[Stakes]
    B --> D[Size: 100×25×6 mm]
    B --> E[Weight Loss Evaluation]
    C --> F[Size: 450×100×75 mm]
    C --> G[Rating Method Evaluation]
    B --> H[18 replicas + 18 controls]
    C --> I[4 replicas]
    H --> J[Inspection at 1,3,5 years]
    I --> J

This ensures standardized specimen preparation and durability assessment per IS 6497.

IS 6497: Numbering of Specimens & Specimen Details

Numbering of Specimens (Clause 4.2)

• Marking Location: Left end of specimen, both sides.
• Number Format: 3 figures
  • 1st figure: Species code
  • 2nd figure: Treatment/Preservative code
  • 3rd figure: Serial number of specimen

Specimen Sizes & Details (Clause 4.1)

• Specimens must conform to IS 2372:1963.
• Defective specimens must be rejected after screening (Clause 4.1.1).

Arrangement for Testing (Clause 4.4.1)

• Use 18 replicas per species and absorption level + 18 control specimens.
• One treated specimen per absorption level + one control fixed on wooden frame (see Fig. 3).
• Reference species: Chir (Pinus Roxburghii Sargent).

Summary Diagram for Numbering

flowchart LR
    A[Specimen] --> B[Left End (Both Sides)]
    B --> C[Numbering: XYZ]
    C --> D[1st digit: Species]
    C --> E[2nd digit: Treatment/Preservative]
    C --> F[3rd digit: Serial No.]

This system ensures clear identification and traceability of specimens during testing.

IS 6497: Preservative Treatment - Key Points

1. Evaluation Methods

• Thin specimens: Weight loss method to measure preservative efficacy.
• Stakes: Rating method based on visual deterioration.
• Specimen size is chosen for high surface-to-volume ratio to accelerate preservative depletion.

2. Natural Durability (Clause 5.1.1)

• Deterioration evaluated similarly by weight loss (thin specimens) and rating (stakes).
• Refer to Table 5 (Natural Durability) for timber classification by durability (not fully provided here).

3. Testing Preservatives (Clause 4.3.1)

• For preservatives not in IS 2372:1963, test at three absorption levels.
• Use Copper-Chrome-Arsenic (CCA) as a reference preservative.

Summary Table: Evaluation Methods

Notes:

• Standard Mark ensures compliance with BIS quality control.
• Testing simulates conditions in cooling towers without heavy deposits.
• Always refer to the latest edition and amendments of IS 6497.

flowchart LR
    A[Timber Specimens] --> B{Specimen Type}
    B --> C[Thin Specimens]
    B --> D[Stakes]
    C --> E[Weight Loss Method]
    D --> F[Rating Method]
    E --> G[Quantitative Evaluation]
    F --> H[Qualitative Evaluation]

For detailed tables and preservative absorption levels, consult IS 6497 and IS 2372:1963 directly.

IS 6497: Preparation of Specimens - Key Points

1. Specimen Sizes (Clause 4.1)

• Thin specimens: 100 mm × 25 mm × 6 mm with two holes of 2 mm diameter (Fig. 1).
• Stake specimens: 450 mm × 100 mm × 75 mm with two holes of 4 mm diameter (Fig. 2).
• Timber must conform to IS 2372:1963.

2. Specimen Preparation (Clauses 4.1.1, 4.7.2)

• Screen specimens carefully; reject defective ones.
• After exposure, clean specimens in tap water.
• Use 0.05% HCl solution if calcareous deposits are present.
• Dry specimens in an oven at 100–105°C until constant weight.
• Apply an adjustment factor to account for weight loss due to preservative leaching or exudation during drying.

3. Specimen Arrangement (Clause 4.4.1)

• Use 18 replicas per species and absorption level, plus 18 control specimens.
• Fix one treated specimen and one control specimen per absorption level on a wooden frame (Fig. 3).
• Use Chir (Pinus roxburghii) as a reference species.

Summary Table of Specimen Dimensions

flowchart LR
    A[Specimen Selection] --> B[Screen & Reject Defective]
    B --> C[Cleaning]
    C --> D{Calcareous Deposits?}
    D -- Yes --> E[Clean with 0.05% HCl]
    D -- No --> F[Clean with Tap Water]
    E --> G[Dry at 100-105°C till constant weight]
    F --> G
    G --> H[Apply Adjustment Factor for Weight Loss]
    H --> I

IS 6497: Installation Key Points

Specimen Sizes (Clause 4.1)

• Thin Specimen:
  • Size: 100 mm × 25 mm × 6 mm
  • Two holes, diameter 2 mm
  • Used for flooded and extremely moist areas
• Stake:
  • Size: 450 mm × 100 mm × 75 mm
  • Two holes, diameter 4 mm
  • Used for alternate drying/wetting regions or structural members

Installation (Clause 4.5.1)

• Frames with Thin Specimens must be installed in:
  • Flooded areas
  • Extremely moist regions of the tower
• Quantity & Location:
  • 9 frames in the fill area or lower inside casing
  • 9 frames on the upper inside casing or lower drift eliminators

Additional Notes

• Brass nails are positioned as per Fig. 1 and Fig. 2 (not shown here).
• Specimens must conform to IS 2372:1963 timber standards.

flowchart LR
    A[Thin Specimen Frame] -->|9 Frames| B(Fill Area / Lower Inside Casing)
    A -->|9 Frames| C(Upper Inside Casing / Lower Drift Eliminators)
    D[Stake] --> E(Structural Members / Alternate Drying & Wetting Areas)

This ensures proper monitoring of timber durability in different environmental conditions per IS 6497.

IS 6497: Inspection and Examination Summary

Specimen Details (Clause 4.1)

• Thin Specimens: 100 × 25 × 6 mm, 2 holes of 2 mm dia (for flooded/moist areas)
• Stake Specimens: 450 × 100 × 75 mm, 2 holes of 4 mm dia (for alternate wet/dry areas)

Inspection Schedule (Clause 4.6.1)

• Inspect installed specimens at 1, 3, and 5 years after installation.
• Third inspection period may be adjusted based on specimen condition.
• For thin specimens, remove 3 frames each from flooded and moist areas for evaluation.

Evaluation Methods (Clause 5.1.1)

• Thin specimens: Weight loss method to assess deterioration.
• Stake specimens: Rating method for deterioration.

Key Evaluation Formula

Weight Loss (%) for Thin Specimens:

[ \text{Weight Loss} = \frac{W_i - W_f}{W_i} \times 100 ]

• (W_i) = Initial weight before exposure
• (W_f) = Final weight after exposure

Inspection Flowchart

flowchart TD
    A[Install Specimens] --> B[Inspect at 1 Year]
    B --> C[Inspect at 3 Years]
    C --> D[Inspect at 5 Years]
    D --> E{Condition Assessment}
    E -->|Good| F[Continue Monitoring]
    E -->|Poor| G[Adjust Inspection Frequency]

Note: Specimens must conform to IS 2372:1963 timber standards and be carefully screened (Clause 4.1.1).

IS 6497 – Evaluating Deterioration of Timber

Key Methods (Clause 4.7 & 3.1)

• Thin specimens:
  • Deterioration evaluated by weight loss (%).
  • High surface-to-volume ratio accelerates preservative depletion.
• Stakes:
  • Evaluated by a rating (grading) method based on visual inspection.

Rating System for Stakes (Clause 4.7.5)

Weight Loss Calculation (for thin specimens)

[ \text{Weight Loss (%)} = \frac{W_i - W_f}{W_i} \times 100 ]

• (W_i) = Initial weight
• (W_f) = Final weight after exposure

Summary:

• Use weight loss % for thin specimens.
• Use grading 1 to 5 for stakes based on visual condition.
• Grade 4 indicates end of useful life.

flowchart TD
    A[Start Evaluation] --> B{Specimen Type?}
    B -->|Thin Specimen| C[Measure Initial Weight \(W_i\)]
    C --> D[Expose Specimen]
    D --> E[Measure Final Weight \(W_f\)]
    E --> F[Calculate Weight Loss %]
    B -->|Stake| G[Visual Inspection]
    G --> H[Assign Grade 1 to 5]
    H --> I{Grade}
    I -->|1 to 3| J[Continue Monitoring]
    I -->|4| K[End of Useful Life]
    I -->|5| L[Complete Destruction]

This ensures consistent evaluation of timber deterioration as per IS 6497.

IS 6497: Natural Durability of Timber - Key Points

1. Evaluation Methods

• Weight Loss Method: Used for thin specimens to measure deterioration quantitatively by weight loss.
• Rating Method: Used for stakes, visually graded from 1 (start of attack) to 5 (complete destruction). Grade 4 indicates end of useful life.

2. Specimen Preparation

• Specimens must be from heartwood.
• Sizes as per Clause 4.1 (not detailed here).
• Number of replicas:
  • Thin specimens: 18 per cooling tower
  • Stakes: 4 per cooling tower

3. Inspection Periods

• Standard: 1, 3, and 5 years after installation.
• If rapid deterioration: 1, 2, and 3 years.

4. Grading Scale for Stakes (Clause 4.7.5)

Summary Table: Natural Durability Testing

flowchart LR
    A[Heartwood Specimens] --> B[Thin Specimens]
    A --> C[Stakes]
    B --> D[Weight Loss Method]
    C --> E[Rating Method (1 to 5)]
    D --> F[Inspection at 1,3,5 years]
    E --> F
    F --> G[Evaluate Natural Durability]

Note: For detailed sizes and preparation, refer to Clause 4.1 of IS 6497.

Evaluation Method per IS 6497

Key Points from Clauses 4.7 & 4.7.4:

• Thin specimens: Deterioration evaluated by weight loss.
• Stakes: Deterioration evaluated by rating method.
• Size/shape of thin specimens ensure large surface-to-volume ratio to accelerate preservative depletion.

Adjustment Value Calculation (Clause 4.7.4):

[ \text{Total dry weight before leaching} = a + b ]

Where:

• (a) = Oven-dry weight before treatment
• (b) = Net retention of preservative (dry salt)
• (c) = Oven-dry weight after 18 weeks leaching in tap water

[ \text{Chemical leached out} = (a + b) - c ]

[ \text{Leached out percentage} = \frac{(a + b) - c}{a + b} \times 100 ]

• Use average of 10 specimens as the adjustment value.

Summary Table:

flowchart TD
    A[Start: Oven-dry weight (a)] --> B[Add preservative retention (b)]
    B --> C[Calculate total (a+b)]
    C --> D[Leaching in water for 18 weeks]
    D --> E[Measure oven-dry weight after leaching (c)]
    E --> F[Calculate chemical leached out = (a+b)-c]
    F --> G[Calculate leached out % = ((a+b)-c)/(a+b)*100]
    G --> H[Average over 10 specimens]

This method ensures reliable evaluation of preservative efficacy and timber durability in cooling towers.

IS 6497: Figures and Specimen Details Summary

Specimen Sizes & Details (Clause 4.1)

• Position of brass nails is specified in figures.
• All dimensions are in millimeters.

Specimen Numbering (Clause 4.2)

• Number stamped on the left end, both sides.
• Format:
  [Species][Treatment/Preservative][Serial Number]

Arrangement for Testing (Clause 4.4.1)

• 18 replicas per species per absorption level + 18 control specimens.
• Mounted on wooden frame (Fig. 3).
• Reference species: Chir (Pinus Roxburghii Sargent).

Evaluation Methods (Clause 5.1.1)

• Thin specimens: Weight loss method.
• Stakes: Rating method.

Quick Reference: Specimen Dimensions

| Specimen Type | Length (mm) | Width (mm) | Thickness (mm) | Hole Diameter (mm) |
|---------------|-------------|------------|----------------|--------------------|
| Thin Specimen | 100         | 25         | 6              | 2                  |
| Stake         | 450         | 100        | 75             | 4                  |

Diagram: Specimen Setup (Conceptual)

graph LR
    A[Wooden Frame] --> B[Thin Specimens (100x25x6)]
    A --> C[Control Specimens]
    B --> D[Brass Nails Position (per Fig. 1)]
    C --> E[Brass Nails Position (per Fig. 1)]

For detailed nail positions and hole locations, refer to Figures 1, 2, and 3 in IS 6497.

Note: Use IS 2372:1963 for timber conformity and ensure