What is the minimum sample requirement for gunning as-installed testing?

The minimum sample requirement for gunning as-installed testing is one sample per each gunning crew per material per shift. This approach is essential because it ensures that each crew is adequately monitored for the quality and consistency of the refractory material being applied. By requiring a sample for each crew, it helps to validate that the gunning application adheres to the necessary specifications and performance standards for that particular shift.

Sampling from each crew also accounts for potential variations in application technique, equipment used, and other environmental factors that may influence the performance of the material. This practice offers a more comprehensive quality assurance process, helping to ensure that the repaired or installed refractory linings will perform reliably under operating conditions.

While the other options may suggest different sampling strategies, they do not provide the same level of assurance and oversight critical to maintaining refractory installation standards during each work shift.