Fireclay refractories: the approximate maximum safe working temperature (continuous service) for standard fireclay bricks is about how many degrees Celsius?

Introduction / Context:
Fireclay bricks are alumino-silicate refractories widely used for furnace walls, flues, and general linings. While laboratory refractoriness (softening under load or pyrometric cone equivalent) can indicate high temperatures, practical “maximum safe working temperature” for continuous service is lower and reflects creep, load, and atmosphere effects.

Given Data / Assumptions:

• Standard fireclay compositions (approx. 25–45% Al2O3, remainder SiO2).
• Continuous industrial service, not brief excursions.
• Moderate load and oxidizing/neutral atmospheres.

Concept / Approach:
Fireclay refractories soften gradually as glassy phases form and viscous flow increases. Although some grades may exhibit refractoriness up to around 1500 °C in short tests, continuous safe working limits are commonly placed nearer 1250–1350 °C for general-duty fireclays. Therefore, ~1300 °C is a widely taught rule-of-thumb for maximum safe working temperature under typical conditions.

Step-by-Step Solution:
Distinguish “refractoriness” from “safe working temperature.”Account for load/creep that lowers usable service temperature.Select 1300 °C as the practical upper bound for standard fireclay bricks.

Verification / Alternative check:
Vendor datasheets and handbooks list service limits near 1200–1350 °C for common fireclay grades, with super-duty/high-alumina bricks covering higher ranges.

Why Other Options Are Wrong:

• 1150: conservative for many standard fireclays.
• 1450/1550/1750: exceed continuous-service capability of typical fireclay; those ranges require high-alumina, silica, or other advanced refractories.

Common Pitfalls:
Confusing cone numbers with continuous service; ignoring load and atmosphere effects on creep.

Final Answer:
1300