Three things decide whether a ceramic part lasts: the material, the design and the conditions it actually runs in.
A good material in a poor design still fails.
So does a good design in the wrong material.
This Blasch white paper looks at what makes a ceramic part last or fail in industrial service. It names three factors: material selection, design integrity and the real operating conditions the part sees, which are rarely the design conditions. Long term performance and uptime come from getting all three right together, not from the best value in any one datasheet.
A ceramic lid that carries its own weight with ease can still break when its top runs only a few degrees hotter than its bottom.
Room temperature values say little about a part that runs inside a furnace. What counts is strength and creep at temperature. A published comparison for reformer tunnel blocks shows the gap: super duty firebrick deflected 7.86% in a creep test at 1,427 °C, mullite bonded alumina 1.11% at 1,649 °C. Hot modulus of rupture was under 600 psi for the brick and 1,700 psi for the mullite bonded alumina.
A published finite element study of a reformer tunnel lid, 9 by 9 by 42 inches, found only about 10 psi of stress from its own weight at a constant 1,900 °F. A temperature difference of 10 °F between top and bottom raised it to about 1,500 psi, more than the hot strength of many refractories. The same study found that a mortared 10 ft wall section exceeds the hot strength of typical mortar, while the same wall built from individual blocks with their own expansion gaps stays below 4.5 bar.
The design lesson: let each part expand on its own, and do not tie parts together with mortar that has to crack. That is the principle behind self-supporting ceramic structures such as the StaBlox tunnel system.
Plants run harder than they were designed for: higher temperatures, longer campaigns, oxygen enrichment with larger temperature swings, start-ups and trips. A part has to be designed for those cycles, not for steady state.
Ask for the data at your temperature and for the failure mode you see. The test and modeling work behind Blasch parts is described on modeling and testing, and the lining side of the argument in Rethinking Refractory Design.
Often because of thermal stress. A temperature difference across a part can create far more stress than its weight.
Hot modulus of rupture and creep at the operating temperature, plus thermal shock resistance where the part cycles.
With finite element analysis for stress and CFD for flow and heat transfer, and in-house tests for thermal shock, creep and strength.
Tell us how it breaks and at what temperature. A Blasch engineer looks at material and design together.
