May I ask that the horizontal distance from the foundation line inside the fire dike to the outer wall of the vertical storage tank should not be less than half of the height of the tank wall; the outer wall of the tank is merely...

The tank wall height refers to the height of the highest point on the outer wall of the storage tank above the ground level. I’m not sure if the original poster understands this; the top head does not need to be taken into consideration.

I haven’t seen a specific definition for this standard; thank you

I checked, and both the building codes and the petrochemical codes contain this provision; the explanation in clause 6.2.13 of the petrochemical codes is also quite clear, focusing mainly on the maximum horizontal distance of spray dispersion. The maximum horizontal distance of spray from a vertical storage tank is, according to the interpretation of the regulations, equal to half the height of the tank wall. By saying the height of the tank wall rather than the actual size of the wall, we mean this: the height of the tank wall = the length of the wall’s own dimensions + the foundation and other elements. Just as in everyday life, the height of a floor is measured starting from the ground level. Another example: in the case of a semi-buried storage tank, the height of its walls is quite small, referring only to the height of the walls that are above the ground surface.

According to the height of the straight edge section + the bottom discharge pipe

Regarding this, experts in formulating fire protection regulations explain that the tank wall height refers to the height of the equipment’s walls, without taking into account the height of the foundation; for special elevated tanks, however, the height of the foundation must be considered. I took a look at the 3 explanations of the provisions; this makes sense as well.