How much of the weld metal must be removed if a complete penetration groove weld has a crack that is 4 inches in length?

In the case of a complete penetration groove weld that has developed a crack, it is critical to ensure that the removal process addresses not only the cracked section itself but also the areas surrounding it to prevent future failures. Removing additional material beyond just the crack helps to eliminate any potential defects that could contribute to further cracking or weaknesses.

Choosing to remove 8 inches, which includes the 4-inch length of the crack plus an additional 2 inches on each end, is a common practice in weld repair. This "beyond the crack" removal provides a margin of safety by ensuring that any stress concentration points or microcracks adjacent to the visible crack are also addressed. Such practices are grounded in weld repair guidelines and industry standards that emphasize the importance of thoroughness in repairs to maintain structural integrity.

The other options do not provide adequate coverage. For instance, removing only the length of the crack itself may leave defects unaddressed, while removing 6 inches or 10 inches may be excessive in certain contexts, potentially leading to unnecessary material loss or misalignment in weld repairs. Thus, the chosen answer strikes a balance between ensuring full integrity and efficiency in the repair process.