API 936 – Refractory Personnel Certification Practice Exam

Flashing is a critical aspect in the realm of refractory installation, particularly when ensuring optimal bond and performance of the materials involved. The reason "flashing" is not permitted after initial set if the surface has been exposed for more than 20 minutes is fundamentally related to the integrity and performance of the refractory layer.

Once the initial set occurs, the surface begins to develop a firm bond and any delay in applying subsequent layers can compromise this bond. If the surface has been exposed for more than the specified time, it can lead to a condition where the surface is no longer suitable for bonding effectively with new materials. This can result in gaps, poor adhesion, and ultimately, reduced performance of the refractory application.

Understanding this helps in recognizing the critical timing required in refractory work to ensure all layers adhere properly and maintain functionality. Thus, respecting the guidelines surrounding the timing of flashing is vital for success in refractory projects.