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 MIL-HDBK-419A
2.2.3 Guidelines for Upgrading.
Use the information available from the corrected drawings and the facility survey to determine if modification
or upgrading of the facility is necessary. Compare the grounding, bonding, shielding, and lightning protection
networks and practices with the recommendations of Chapter 1 of this volume. While making these
comparisons, be particularly alert for indications of operational, installation, or maintenance problems (either
with a system or with an equipment) which may be directly or indirectly related to a noted deficiency. Where a
need for upgrading is indicated, determine what retrofit steps would be necessary and estimate the costs. If the
operational mission of the facility justifies the cost, proceed with the implementation.
The following guidelines may be used to help evaluate the survey findings and to help define the retrofit steps
which should be taken. This set of guidelines is not to be considered as all inclusive. Specific situations can be
expected to arise that will not be adequately covered by the guidelines. These situations must be recognized
and dealt with on an individual basis.
a.
If the measured resistance of the earth electrode subsystem is greater than 10 ohms, review Section
1.2.1 to help identify the reason for the high resistance (see also Volume I, Section 2.3). In addition, review the
past record (if available) of earth resistance measurements for signs of gradual increases in resistance as well
as sudden resistance changes. (Discard from consideration "zero" resistance readings and other similarly
unobtainable values. Review Section 2.2.2.2.1 for the correct measurement procedure.) Examine the resistance
readings for possible correlation with site changes (Section 1.2.1.3) and local climatic conditions (Section
1.2.1.4). Either of these situations could produce an increase in the resistance of the electrode and necessitate
upgrading the system to reachieve 10 ohms.
b.
Once the reason for the high resistance is established, determine the most appropriate method in
terms of cost and ease of implementation for reducing the resistance. Typical alternatives include the use of
more or longer ground rods, the installation of horizontal grids or wires (Section 1.2.2.3), chemical salting (see
Volume I, Section 2.9.3), or the drilling of wells down to the permanent water table.
c.
Carefully review the building drawings to insure that proper connections to the earth electrode
subsystem are provided for all elements of the facility (see Sections 1.2.3, 1.3.2.2.2, and 1.5). For example,
where building expansions have occurred or major equipment additions or relocations have been made, the earth
electrode subsystem should be expanded to serve the new areas. Where such expansions are made, they should
conform to Section 1.2.3.
d.
All specific earth electrode subsystem installation deficiencies such as grounding conductor sizes
not in conformance with MIL-STD-188-124A requirements or maintenance deficiencies such as loose or
corroded bonds and fasteners should be corrected as soon as possible.
e.
If no lightning protection subsystem exists for the structure, consult Volume I, Section 3.8 for
guidance in determining whether a subsystem needs to be installed. If a new subsystem is installed, it should
conform to the recommendations of Section 1.3.
f.
Where a structural lightning protection subsystem exists, all deficiencies noted during the survey
should be corrected. For example:
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