UE guarantees that there won't be any contamination of the cylinder's interior or contents.
No submerging required - because UE uses sound waves, or ultrasound, to look for defects, there is no need to submerge cylinders in water.
Maintains a pristine environment - since the valve isn't removed from the cylinder's neck, there is less opportunity for contaminates to enter the cylinder's interior. Elimination or reduction of these contaminates ensures a higher quality of gas and less ptential in-service damange. This is particularly important for medical, specialty, and electronic gas users.
No baking needed - again, since no water is introduced to the interior, there is no need to bake out the cylinder to remove water traces.