How to read a refractory test certificate

Every consignment of refractory should come with a test certificate. The numbers on it tell you whether the material matches what you ordered and how it will behave in service. Here is what the common values mean.

Chemical analysis

Shows the main oxides as percentages. For fireclay and high alumina bricks, Al₂O₃ (alumina) is the key figure, since it largely decides the grade. Fe₂O₃ (iron oxide) and alkalis are impurities; lower is generally better, especially under reducing conditions or at high temperature.

Bulk density and apparent porosity

Bulk density is the weight of the brick per unit volume. Apparent porosity is the share of open pores. Dense bricks with low porosity resist slag and gas penetration better; insulating bricks are deliberately light and porous so they conduct less heat.

Cold crushing strength (CCS)

The load a brick can take at room temperature before crushing. It indicates how well the brick was pressed and fired, and how it will handle handling, transport and mechanical load.

Refractoriness (PCE)

The pyrometric cone equivalent indicates the temperature at which the material softens under heat alone. It is a basic check of grade, but it does not tell you how the brick behaves under load.

Refractoriness under load (RUL)

The temperature at which the brick starts to deform under a fixed load. This is usually more useful than PCE for walls and roofs that carry weight at high temperature.

Permanent linear change (PLC)

How much the brick permanently expands or shrinks after reheating to a set temperature. Large shrinkage opens joints in service, so a low PLC means a more stable lining.

Thermal conductivity

Mainly relevant for insulating materials. The lower the value at your operating temperature, the better the material insulates.

What to check on delivery

• Grade and specification match your purchase order
• Values are within the range of the relevant standard or data sheet
• Batch or lot numbers match the marking on the material
• Certificate is dated and signed by the manufacturer

JISPL supplies test certificates with every consignment. If any value is unclear, ask us and we will explain it.