Double groove joints always require:

Double groove joints necessitate the weld to be deposited from both sides to ensure a complete and robust connection. This type of joint typically has grooves on both the top and bottom surfaces, which allows weld material to fill both sides of the joint effectively. By depositing weld on both sides, the integrity of the weld is enhanced, resulting in a stronger bond that is essential in applications where the joint must withstand significant loads or stress.

Other options may involve techniques or processes that are beneficial in certain contexts, but they are not requirements for welding double groove joints. While a separate weld procedure could be beneficial, it is not always mandatory. Back gouging is a technique used to prepare the base material for further welding but is not a defining characteristic of double groove joints. The twin arc welding process is a specific method that could be applied in some situations but is not universally required for all double groove joints. Thus, the correct understanding revolves around the need to deposit weld from both sides to achieve the desired joint characteristics.