Loss of refractory as fragments or slabs break away from the hot face. Thermal spalling comes from steep or sudden temperature changes; mechanical or pinch spalling from compressive stress when expanding brick has no room; structural spalling, or peeling, from a slag- or vapor-infiltrated layer that has different properties from the brick behind it. Reading the spall shape and depth usually tells you which cause it was.
Spalling on the hot face is coming off in clean slabs about an inch thick, that's structural, the slag's soaked in.
Read the spall face: a flat slab parallel to the hot face usually means structural spalling, while broken edges at joints point to pinch.
Also heard as
- spall
- peeling
- pinch spalling
- thermal spalling
Related terms
Thermal shock resistance
Ability of a refractory to survive rapid temperature changes without cracking and spalling.
Explosive spalling
Violent failure of a castable during first heat-up when trapped steam pressure blows the lining apart.
Expansion joint
Gap deliberately left in a lining so bricks or castable can grow with heat without crushing or lifting.
Slag attack
Chemical dissolution and penetration of a refractory by molten slag, the main wear mode in metal processing.
Same word, different worlds
Flaking of large chunks from a bearing race or gear tooth after fatigue cracks below the surface link up.
Thermal SprayFlakes or chunks of coating breaking away from the surface, typically under thermal cycling or impact.
Gear EngineeringLarge, irregular flakes broken out of a tooth surface, usually where pits have grown and joined.
Concrete & CementChunks or flakes breaking away from a concrete surface or edge, often from corroding rebar beneath.
Sealants & WaterproofingConcrete, brick or stone breaking off in flakes or chunks at the surface.