Page 98 - 35_DS702_E_2014_Lightning_Protection_Guide

5.2.2.2 Natural components of a down
conductor
l 1
When using natural components of the structure as a down
conductor, the number of separately installed down conduc-
s l 2 tors can be reduced or, in some cases, no separately installed
down conductors are required.
The following parts of a structure can be used as natural com-
ponents of the down conductor:
l 3
¨ Metal installations
These components can be used as natural down conductors
Figure 5.2.2.1.1 Loop in the down conductor
provided that the various parts are safely connected on a
permanent basis and their dimensions meet the minimum
requirements for down conductors. These metal installa-
It is recommended to mount down conductors in such a way tions may also be incorporated into insulating material.
that the required separation distance s is maintained from all It is not permitted to use pipelines containing flammable
doors and windows (Figure 5.2.2.1.2). or explosive materials as down conductors if the seals in
Metal gutters must be connected with the down conductors at the flanges / couplings are non-metallic or the flanges / cou-
the points where they intersect (Figure 5.2.2.1.3). plings of the connected pipes are not conductively con-
The base of metal downpipes must be connected to the equi- nected in any other way.
potential bonding or earth-termination system, even if the ¨ Metal framework of the structure
downpipe is not used as a down conductor. Since it is connect- If the metal framework of steel frame structures or the in-
ed to the lightning current carrying gutter, the downpipe also terconnected reinforcing steel of the structure is used as
carries a part of the lightning current which must be diverted a down conductor, ring conductors are not required since
to the earth- termination system. Figure 5.2.2.1.4 illustrates additional ring conductors would not improve the splitting
a possible design. of the current.

s

Connection must be Only soldered or riveted Figure 5.2.2.1.3 Air-termination system
as short as possible, downpipes may be used connected to the gutter
straight and vertical as a down conductor

s s

Figure 5.2.2.1.4 Earth connection of a
Figure 5.2.2.1.2 Down conductors downpipe

www.dehn-international.com LIGHTNING PROTECTION GUIDE 97