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 MIL-HDBK-419A
2.2.2.2.3 Lightning Protection Network.
a.
First, make a sketch of the lightning protection network for the facility or compare the system as
installed with the engineering drawings.
(1) The sketch should include profile views of the facility's exterior either drawn approximately to
scale or dimensions indicated on the views to permit scaled drawings to be made later. On the sketch, indicate
the location of air terminals (lightning rods), the routing of roof and down conductors, connections to the earth
electrode subsystem, and the location and size of bonding jumpers. Are the air terminals located and installed
in such a manner so as to provide adequate protection (1:1 cone of protection) for all C-E buildings, structures,
antennas, and equipments?
(2) In most cases, engineering drawings should be available. If not shown already, add elements of
the lightning protection subsystem to the drawings.
b.
Some large existing facilities may have a UL Master Labeled System installed. If such a system
exists, indicate this fact in Section B, Part III of the Form.
c.
In Section C, Part III, of the Form, record the height (above the roof) and material of the air
terminals. Look for evidence of burning, pitting, or melting of a degree that seriously weakens (physically) the
air terminals. While inspecting the air terminals, be alert for other metallic extensions (railings, antenna
masts, etc.) extending above the air terminals or outside the cone of protection and note the existence of any
such extensions on the Form.
d.
Record the cable sizes and materials used for roof and down conductors. Examine both types of
conductors for unnecessary length, sharp or unnecessary turns (radii less than 20 cm (8 inches)), corrosion, and
mechanical damage.
e.
Check fasteners and mounting hardware for secure mounting, looseness, corrosion, and mechanical
damage. Verify that fasteners for connecting dissimilar metals (e.g., copper to aluminum) are of UL-approved
bimetallic construction. Record any noted deficiencies in Section F, Part III, of the Form.
f.
Be sure that the bonds and bonding inspection (Section 2.2.2.2.2) includes the lightning protection
subsystem.
g . Insure that interconnections between the lightning protection subsystem and the earth electrode
subsystem, structural metals, utility lines, etc., are recorded or noted on the sketch prepared earlier or are
shown on the facility drawings.
h.
Check for the adequacy of guards which provide mechanical protection for down conductors (see
Figure 2-8). Note any down conductors in areas with public access or subject to contact by equipment or
machinery. All such down conductors must be guarded with- metallic or nonmetallic (preferably) guards to a
height of at least 2.7 meters (9 feet) from grade or floor level. Such guards must be securely fastened in place
and not show appreciable physical degradation. Metal guards to include EMT and conduit must be bonded to the
down conductor at the top and bottom. Record all noted deficiencies in Section H, Part III.
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