Upon welding in light moisture conditions, when must the thermite weld be covered?

The correct answer pertains to the need for providing protection to the thermite weld following the shearing process. When welding in light moisture conditions, covering the weld immediately after shearing is essential to prevent moisture intrusion, which can compromise the integrity of the weld joint. Exposure to moisture can lead to various issues, such as weakening the bond or initiating corrosion at the weld site.

Covering the weld after shearing ensures that the structural integrity is maintained and that the weld is not adversely affected by environmental factors. It is also critical at this stage to account for any potential reactions between the molten metal and moisture, which could weaken the weld further.

Considering the other options, covering immediately before pouring does not address the need for protection in relation to moisture exposure as it misses the critical phase of handling post-shear. Similarly, covering after a cooling period may allow sufficient time for moisture to impact the weld if it is not adequately protected right after shearing. Covering after the initial setup also fails to address the timing associated specifically with the moisture concerns during and after shearing. Thus, covering post-shearing is the most vital step in ensuring a quality thermite weld under those conditions.