What are the two primary concerns when welding on in-service piping and equipment?

The correct response highlights the significant issues encountered during welding on in-service piping and equipment, specifically burn through and cracking.

When welding occurs on in-service components, one of the primary concerns is burn through. This happens when excessive heat is applied during the welding process, which can lead to penetration through the wall of the pipe or container, causing structural integrity issues or leaks in the system. In-service piping often contains fluids under pressure, and burn through can create hazardous situations, including leaks or catastrophic failures.

Cracking is another major concern. The heat from welding can change the microstructure of the material, especially in high-stress areas, leading to the formation of cracks. These cracks may become more pronounced under operational conditions, as they can negatively impact the material's mechanical properties and lead to failure over time.

Thus, the combination of these two factors—burn through and cracking—makes them the primary concerns during welding on in-service piping and equipment, ensuring both safety and compliance with operational standards. In contrast, while distortion, stress, oxidation, corrosion, hardening, and the heat-affected zone are all relevant considerations in welding, they are secondary to these immediate risks when addressing in-service operations.