Quantcast Chapter 2 Existing Facilities

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MIL-HDBK-419A
CHAPTER 2
EXISTING FACILITIES (Not Protected Against EMP)
2.1 INTRODUCTION. This chapter presents steps and procedures for verifying, upgrading, and evaluating the
grounding, bonding, and shielding networks in an existing facility not protected against EMP. The specific items
to consider during the evaluation of the facility are identified in Section 2.2 with a suggested survey form
provided in Section 2.2.2.4. In addition, inspection procedures are given in Section 2.3. These procedures are
directed toward verifying that the grounding, bonding, and shielding networks have not been compromised, that
the basic resistance goals continue to be met, and that corrosion is effectively controlled.
2.2 UPGRADING.
For an existing facility with electrical wiring already installed, with an earth electrode subsystem (frequently
only a connection to the water system) present, and (commonly) with electrical/electronic equipments in place,
the installation of the grounding, bonding, and shielding networks described in Chapter 1 may not be
straightforward. In recognition that major retrofitting, with the attendant costs and operational disruption,
may be required in order for the facility to conform to the recommended practices and procedures, it is
necessary that a comprehensive grounding, bonding, shielding, and lightning protection survey be made of the
entire facility.  The findings of the survey should be entered on the Survey Form. The results should be
critically analyzed to determine the extent to which the existing system fails to conform to the
recommendations set forth in Chapter 1. In areas of nonconformance, the performance history of equipments
and subsystems in the facility should be examined to establish, if possible, any relationships which exist between
noted deficiencies and operational problems.  Then the decision to retrofit and the extent of any such
retrofitting can be made based on the relative need to improve and on the overall cost of the retrofit. Figures
2-l and 2-2 are typical for building expansion.
Before upgrading, altering, or expanding the grounding, bonding, or the shielding of a facility, it is necessary to
define and analyze the existing system. This definition and analysis should include as a minimum the following
steps:
a.
Obtain or prepare an accurate and complete set of drawings to show what is initially in the facility.
b.
Determine the condition, integrity, and effectiveness of the grounding, bonding, and shielding
systems as they exist before changes are made. This determination will usually consist of a combination of
visual inspections, analyses of facility drawings, and electrical measurements.
Comprehensively document the findings of steps a and b and maintain for future reference.
c.
d.
Compare the findings with the facility requirements to determine if improvements are needed.
Once the need for changes or improvements in the system is determined, take whatever action is needed to
rectify the deficiencies noted during the survey.
2-1





 


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