From each production run, the testing frequency for erosion service refractory is one sample per:

API 936 establishes quality assurance testing frequencies based on usage, service condition, and criticality of application. Forerosion service refractory, which is subject to high-velocity particle impingement (e.g., in FCCU units), the standard testing frequency isone sample per 2 tons or less. This ensures that each significant quantity used in fabrication is represented by a test sample to verify compressive strength, density, and abrasion resistance.

Failure to meet this frequency may risk undetected variability in raw material batches or mixing inconsistencies.