The term "production run" is defined by API 936 as follows:
"Production Run: The quantity of material manufactured using the same formulation in an uninterrupted manufacturing operation."
- API Std 936, Section 3: Terms and Definitions
This distinguishes it from a test sample (a subset), a pallet (a packaging unit), or a bag (a smaller containment unit). The production run forms the batch basis for qualification and traceability.

Hydraulic bonded castables, such as those using calcium aluminate cement, cure through ahydration reactionthat requires the presence of water. Premature drying due to wind, sun, or heat can halt the hydration process, weaken the structure, and cause surface cracking. API 936 mandates thatno part of the exposed surface of the castable shall be allowed to dry more than 3 hoursbefore a membrane curing compound is applied.
This statement ensures:
Retention of sufficient surface moisture for ongoing hydration.
Prevention of microcracking, which can later act as stress risers during service.
Uniform strength development across the lining.
The curing compound forms a film that limits evaporation, allowing for continued hydration over the next 24-
48 hours.
Reference:
API Std 936, Section 6.3.2: "No portion of the exposed surface shall be allowed to dry more than 3 h prior to the application of the curing compound." ASTM C309(Referenced Standard): Specifies the performance requirements for curing compounds used in cement-based materials.