Permanent Linear Change: Why the Test Temperature Matters
Read PLC values with their firing temperatures and sign before using them in lining comparisons.
Permanent linear change, often shortened to PLC, reports the lasting dimensional change after a specimen is heated and cooled under a defined test. The sign matters: negative values describe shrinkage and positive values describe expansion. A number without its firing temperature is incomplete.
Compare the same exposure
A PLC value after 800°C cannot be ranked directly against one after 1,600°C. Check specimen preparation, soak, and measurement method. If a datasheet gives a range, record the range rather than turning it into a single average for a supplier comparison.
Link the value to construction
Shrinkage or expansion can affect joints, anchors, and interfaces between lining layers. The lining designer needs the relevant temperature profile and geometry, not just a material ranking. A low PLC figure also does not remove the need for expansion allowance or a controlled heat-up plan.
When reviewing a proposed grade, keep the PLC test condition beside density and strength results. Browse Royal's product data and discuss unusual movement or cracking with the technical team.