How should Permanent Linear Change test specimens be measured?

The measurement of Permanent Linear Change test specimens is critical for assessing the dimensional stability of refractories after they undergo high-temperature exposure and subsequent cooling. The standard practice involves measuring the specimens along the longest dimension, which is typically the length of the specimen. In this case, measuring along the 9-inch dimension at the corners is the appropriate method. This approach captures the effects of thermal expansion and contraction more accurately by reflecting the maximum deviation, which can occur along the longest surface of the material.

By focusing on the corners and ensuring that the longest dimension is measured, the test provides a reliable indicator of how much the material changes size due to thermal stresses encountered during use. This is essential for ensuring the quality and longevity of refractory materials in industrial applications, as the goal is to evaluate how these materials hold up under high temperatures without significant dimensional instability.