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 Section 5:
CONSTRUCTION PHASE
5.1
Introduction. As the use of sensitive communication/electronic
equipment has increased the need for electromagnetic compatibility or radio
frequency interference (EMC/RFI), the shielding of enclosures by Naval shore
facilities has grown. There are two major reasons for installing a shielded
enclosure in a shore facility:
a) to exclude external electromagnetic energy from entering a
sensitive area such as a laboratory where very sensitive electronic equipment
is used to measure small signals, and
b) to prevent electromagnetic signals generated in an area from
escaping, such as an area where classified information is being processed.
There are a variety of construction techniques and materials used in the
construction of shielded enclosures, including screen rooms, foil rooms,
bolt-together (demountable) rooms and welded steel rooms. This handbook deals
primarily with demountable and welded steel shielded enclosures. Regardless
of the type of construction, the quality of the material and the workmanship
of the shielding contractor are critical considerations in the construction of
shielded enclosures. Frequent inspection by a qualified government
representative is vital to assure that the overall shielding system is
installed in accordance with the plans, specifications and the approved
submittals.
5.1.1
Shield Effectiveness Testing. Testing of the shielded enclosure
both during construction and after the shielded enclosure is assembled is a
must. Often, leaks in a shielded enclosure cannot be detected by visual
inspection. Therefore, testing is required using specialized electronic
equipment operated by qualified personnel. These tests must be accomplished
before any finishes are applied. Once the finishes are on the walls and
ceiling it is more difficult to determine the path of the leakage, and it is
both costly and time consuming to remove finishes to repair leaks in the
enclosure.
5.2
Submittals. Prior to allowing the contractor to begin working on
the shielded enclosure, all of the submittals must be reviewed and approved by
a qualified person. The submittals usually include shop drawings, catalog
data, instruction handbooks, certificates of conformance or compliance, a
testing plan, certified test reports, samples and construction schedules.
5.2.1
EMI Test Module. In the case of large shielded enclosures the
project may include a sample test module, a small version of the enclosure
approximately 8 ft cube. The contractor shall also submit an EMI Test Module
Fabrication and Testing Plan to the Resident Officer in Charge of Construction
(ROICC) for comment and approval. The test module must include the same
materials and techniques to be used in construction of the project enclosure
and must include samples of all typical floor, wall, and roof seams and all
nontypical seams at corners and floor/wall and roof/wall junctions. The
module must also include a typical EMI door, power filter, HVAC waveguide,
floor & roof drain (if there will be any in the facility), and a sample of all
other penetrations which will be made in the facility. All methods of
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