You know very well that some objects expand on heating.Similarly refractories also expand on heating. So it was recommended to provide expansion provisions for their expansion.
What happens if refractory was not provided with proper expansion provision?
If no expansion provision was provided,then it results in refractory cracking.
How to provide expansion provision for refractories?
General thumb rule for all refractory expansion provisions:
For each one meter, provide 2 to 3 mm of cardboard/plywood material. This expansion system applies for almost all refractory systems and it can solve major expansion problems.
The following diagram makes you understand easily :
