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IS 6497 : 1990Method of test for the efficacy of preservatives and evaluating the natural durability of timbers used in cooling towers

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EN 807 · EN 84 · ASTM D1413-07(2021)
CurrentSpecializedTesting MethodMaterials Science · Timber and Timber Stores
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Link points to Internet Archive / others. Not hosted by InfraLens. Details
OverviewValues7InternationalTablesFAQ4Related

IS 6497:1990 is the Indian Standard (BIS) for method of test for the efficacy of preservatives and evaluating the natural durability of timbers used in cooling towers. This standard specifies a laboratory method to test the effectiveness of wood preservatives and to determine the natural durability of timber species intended for use in cooling towers. The test simulates the unique environment of a cooling tower, involving continuous water flow and exposure to soft rot microorganisms, to assess material degradation.

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

Overview

Status
Current
Usage level
Specialized
Domain
Materials Science — Timber and Timber Stores
Type
Testing Method
International equivalents
EN 807:2013 · CEN (European Committee for Standardization), EuropeEN 84:1997 · CEN (European Committee for Standardization), EuropeASTM D1413-07(2021) · ASTM International, USAASTM D2017-05(2021) · ASTM International, USA
Typically used with
IS 401IS 1708IS 218
Also on InfraLens for IS 6497
7Key values1Tables4FAQs
Practical Notes
! This is an accelerated test method that simulates the biological attack (specifically soft rot fungi) on timber inside a cooling tower.
! The results are comparative and are used to rank the performance of different timber species or preservative treatments under controlled laboratory conditions.
! This standard was reaffirmed in 2021, indicating its continued relevance without any technical updates.
Frequently referenced clauses
Cl. 3Test SpecimensCl. 4ApparatusCl. 5Test ProcedureCl. 6Evaluation of Results
Pulled from IS 6497:1990. Browse the full clause & table index below in Tables & Referenced Sections.
timberwood preservatives

International Equivalents

Similar International Standards
EN 807:2013CEN (European Committee for Standardization), Europe
MediumCurrent
Wood preservatives - Determination of the toxic effectiveness against soft rotting micro-fungi and other soil inhabiting micro-organisms
Tests preservative efficacy against soft rot using an unsterilized soil bed, a key decay type in cooling towers.
EN 84:1997CEN (European Committee for Standardization), Europe
MediumCurrent
Wood preservatives - Accelerated ageing of treated wood prior to biological testing - Leaching procedure
Specifies a leaching pre-treatment, which is an integrated part of the IS 6497 test procedure.
ASTM D1413-07(2021)ASTM International, USA
LowCurrent
Standard Test Method for Wood Preservatives by Laboratory Soil-Block Cultures
A fundamental lab method for preservative efficacy, but uses pure fungal cultures and soil contact, not a simulated water-spray environment.
ASTM D2017-05(2021)ASTM International, USA
LowCurrent
Standard Test Method for Accelerated Laboratory Test of Natural Decay Resistance of Woods
Covers the evaluation of natural durability, but uses a standard soil-block method rather than a cooling tower simulation.
Key Differences
≠IS 6497 uses a unique custom-built apparatus to simulate the cooling tower environment with continuous hot water spray, integrating decay and leaching. International standards typically separate leaching (e.g., EN 84) from the biological test (e.g., EN 807, ASTM D1413), which is conducted in soil beds or on agar.
≠The Indian standard uses unsterilized, non-standardized garden soil as a source of mixed micro-flora. In contrast, standards like ASTM D1413 mandate the use of specific, pure strains of wood-destroying fungi, while EN 807 uses unsterilized soil with specified properties (pH, water holding capacity).
≠The test temperature in IS 6497 is elevated (40 ± 2 °C) to simulate cooling tower conditions. Most international lab decay tests, such as ASTM D1413 and EN 807, are conducted at a lower, near-optimal temperature for fungal growth (around 27 °C).
≠IS 6497 is an integrated test method for a specific end-use application (cooling towers). The international approach is more modular, where results from separate tests (leaching, soft rot, brown rot) are combined to assess suitability for a given Use Class or Hazard Class.
Key Similarities
≈The primary criterion for evaluating durability and preservative efficacy in all compared standards is the percentage of mass loss of the wood specimens after the test period.
≈All methods require the inclusion of untreated, non-durable wood specimens (e.g., Semul in IS 6497, Pine/Beech sapwood in EN standards) as 'feeder' or 'control' blocks to verify the virulence of the biological attack during the test.
≈All standards specify rigorous procedures for the initial and final conditioning and weighing of test specimens to ensure accurate and reproducible calculation of mass loss, typically involving oven-drying to a constant weight.
≈The overall objective is shared: to provide a laboratory-based, accelerated method to compare the relative performance of different wood species or preservative treatments against microbiological degradation.
Parameter Comparison
ParameterIS ValueInternationalSource
Test Specimen Size (mm)100 x 25 x 650 x 25 x 15EN 807
Test Specimen Size (mm)100 x 25 x 619 x 19 x 19 (cube)ASTM D1413
Test Temperature40 ± 2 °C27 ± 2 °CEN 807
Test Duration (Preservative Efficacy)12 weeks12 weeksEN 807 / ASTM D1413
Inoculum SourceUnsterilized garden soilPure cultures of specified fungiASTM D1413
Inoculum SourceUnsterilized garden soilSpecified unsterilized test soil (loam based)EN 807
Leaching ProcedureIntegrated into test via continuous water spraySeparate pre-test procedure over 14 daysEN 84
Reference Timber for Test ValidationSemul (Bombax ceiba)Beech (Fagus sylvatica)EN 807
⚠ Verify details from original standards before use

Key Values7

Quick Reference Values
Standard test specimen size100 mm x 25 mm x 6 mm
Number of specimens per test set10
Standard test duration12 months
Water flow rate in apparatus20 to 25 litres/h
Mass loss for Class I (Very Durable) timber< 5%
Mass loss for Class II (Durable) timber5 to 10%
Mass loss for Class V (Perishable) timber> 30%
Key Formulas
Percentage mass loss = ((W1 - W2) / W1) * 100 — Where W1 is initial oven-dry mass and W2 is final oven-dry mass after test.

Tables & Referenced Sections

Key Tables
Table 1: Durability Classification Based on Mass Loss
Key Clauses
Clause 3: Test Specimens
Clause 4: Apparatus
Clause 5: Test Procedure
Clause 6: Evaluation of Results

Related Resources on InfraLens

Cross-Referenced Codes
IS 401:2001Code of Practice for Preservation of Timber
→
IS 1708:2014Methods of Testing Small Clear Specimens of T...
→
IS 218:2014Glass Beads for Road Marking
→

Frequently Asked Questions4

What is the primary purpose of this test?+
To evaluate the resistance of timber (natural or treated) to soft rot decay under conditions simulating a cooling tower environment.
How is the durability of timber classified after the test?+
It is classified based on the percentage mass loss after the test. For example, Class I (Very Durable) corresponds to less than 5% mass loss, as per Table 1.
What are the standard dimensions of the timber test specimen?+
The standard test specimen size is 100 mm x 25 mm x 6 mm, as specified in Clause 3.1.
How long does the test take?+
The standard duration for the test procedure is 12 months, according to Clause 5.11.

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