lightning protection for water steel tanks and zone of protection 1

[mabdelsattar]

We have steel water tank with 100m diameter and 23m height above the ground level. Also, we have two rooms 40m and 46m far from the steel tank. The inquiries are:
1- Should I make air terminal for lightning protection above the steel tank or itself protected as the steel sheet of tanks have thickness not less than 5mm and only bonded the tank bottom sheets to ground terminal.
2- Should I make lightning protection for those two concrete rooms (each 6m height and far from tank 40m, 46m respectively) or they locate in the protection zone of tank and don’t need lightning protection.
Thank for all in advance

 

[ScottyUK]

What code or standard are you working to?

 

[waross]

One theory of lightning protection is that air terminals primarily avoid strikes rather than conducting them. They still may take a hit, but many strikes may be avoided.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[mabdelsattar]

Standards: Comply with IEC/BS EN 62305 " Protection of Structures Against Lightning.

 

[ScottyUK]

Oh, the new standard. The old BS 6651 standard allowed use of the rolling sphere method which was fairly straightforward and could be easily assessed without modelling. The new one isn't a user-friendly standard.

The tank should be self-protecting, but my gut feeling is that the other structures will need independent protection unless they are an area where they're protected by a taller structure.

You'll have to consider the effects on devices sensitive to high energy impulses, such as electronic equipment, which wasn't present in BS 6651.

 

[7anoter4]

I have not BS EN62305-3 with me, but I have IEC 62305-3/2006 and I think it could be the same:
IEC 62305-3 Protection against lightning Part 3hysical damage to structures and life hazard.
5.2.5 Natural components
The following parts of a structure should be considered as natural air-termination components
and part of an LPS in accordance with 5.1.3.
a) Metal sheets covering the structure to be protected provided that its electrical continuity is assured by correct means and the thickness it is not less than 4 mm.
5.3.5 Natural components
The following parts of the structure should be considered as natural down-conductors:
a) the metal installations provided that its electrical continuity it is provided [by correct means as welding, brazing etc.]
However, the definition "metal installations" chpt.3.18 does not include tank metallic structure.
The protected distance is considered by using rolling sphere ,protecting angle and mesh methods.
For our case the distance will be 9.5 m rolling sphere and 9.8 m protected angle[in my opinion] for level I [LPL] case.

 

[mabdelsattar]

Thanks to all for enriching the discussion