paragraph is one successful example. Site-specific
methods must be edited at this point in this
specification. Note that all attachment
penetrations must be welded closed. Metal wall
studs or furring strips should be of equal or
greater thickness (gauge) than the shield steel when
shield steel is welded to supporting metal.
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Continuous [1.613] [_____] mm [16] [_____] gauge thick furring channels
spaced not more than 600 mm 24 in on center shall be secured to steel wall
studs by using self-tapping sheet metal screws. The steel sheets shall be
tack welded to the furring strips every 400 mm 16 in on center horizontally
and 600 mm 24 in on center vertically. A continuous full penetration EM
weld shall be made to join the sheets and form the shield. Welds shall not
form dimples or depressions causing fish mouths at the edge of the sheet.
3.2.7
Formed Closures
Formed closures shall be installed where indicated and/or necessary to
completely close all joints, openings, enclosures of pipe chases, and
structural penetrations, columns, and beams.
3.2.8
Sequence of Installation
Erection of the steel shall be sequenced to prevent steel sheet warpage.
Shielding components shall be installed and shall have passed initial
testing (part 1) before construction of any features that would limit
access for repairs to the shield.
3.2.9
Door Assemblies
Doors shall be mounted to perform as specified. Door framing shall be
continuously welded to the EM shield. The structural system supporting the
door frame shall provide proper support for doors and frame.
3.3
EM SHIELDING ENCLOSURE INSTALLATION (BOLTED CONSTRUCTION)
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NOTE: Either welded construction or bolted
construction will be used. Choose the appropriate
construction and delete the non-applicable paragraph.
For the EM shielding enclosure, choose either welded
or bolted construction. The unused method should be
deleted from the project specification. Welded
construction will usually consist of continuous
1.897 mm (14 gauge) thick steel plate and angles to
form the enclosure. Thicker material may be used if
it is more cost-effective or required for structural
reasons. Welded construction is used when a
shielded facility requires a long maintainable
service life of high-level protection, 100 dB
attenuation, or HEMP protection, 100 dB. Bolted
construction is associated with a lower level (50
dB) of maintained shielding effectiveness. Bolted
construction will usually consist of modular panels
bolted together with metal strips or channels.
Panels are commonly plywood with steel sheets
SECTION 13095A
Page 47
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