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.

IS 6497

: 1990

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

CurrentSpecializedTesting MethodMaterials Science · Timber and Timber Stores

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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

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.

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.