Permanent Linear Change (PLC) is a factor used to judge the suitability of refractories in ranges of temperature limits. Refractory materials can undergo mineral formation, phase transformation or shrinkage when heated. These processes may result in either volume expansion or reduction. Upon cooling to room temperature, the material will possibly be larger or smaller than the original dimensions. PLC is the property of shaped refractory to retain their original size after undergoing through a given temperature-time treatment and subsequent cooling down to room temperature. It is a crucial parameter for the design of refractory lining.
The EN 993-10 Standard was issued in 1998 and is based on the PRE/R19 elaborated in 1972.