structural core of either plywood or hardboard. Panels shall have a flame
spread rating of less than 25 when tested according to ASTM E 84. Flat
steel shall conform to ASTM A 653/A 653M with G-60 coating, minimum 0.5512
mm 26 gauge thick, zinc-coated phosphatized. Plywood shall conform to PS1
for exterior, sound grade hardwood, Type I. Hardboard shall conform to AHA
A135.4, Class 4, SIS, for standard type hardboard. Adhesive for laminating
steel sheets to structural core shall be a waterproof type which maintains
a permanent bond for the lifetime of the enclosure.
2.4.2
Framing
Panels shall be joined and supported by specially designed framing members
that clamp the edges of the panels and provide continuous, uniform, and
constant pressure for contact to connect the shielding elements of the
panels. The walls shall be self supporting from floor to ceiling with no
bracing. Deflection of walls under a static load of 335 N 75 pounds
applied normally to the wall surface at any point along the framing members
shall not exceed 1/250 of the span between supports. [Ceilings shall be
self-supporting from wall to wall.] [Ceilings shall be supported by
adjustable, nonconducting, isolated hangers from the structural ceiling
above.] Ceilings shall be designed to have a deflection under total
weight, including ceiling finish, of not more than 1/270 of the span. A
one-piece factory pre-welded corner section or trihedral corner framed with
a brass machine cast corner cap assembly consisting of inner and outer
parts shall be provided at all corner intersections of walls and floor or
ceiling. The modular enclosure shall be designed for ease of erection,
disassembly, and reassembly.
2.4.3
Channel
The framing-joining system members shall consist of 3 mm 1/8 inch thick
zinc-plated steel channels having a minimum 16 mm 5/8 inch overlap along
each side of the contacting surface. Screw fasteners shall be spaced at 75
or 100 mm 3 or 4 inch intervals. Screw fasteners shall be either zinc or
cadmium-plated steel, minimum size 6 mm 1/4 inch - with a pan or flat
Phillips head. Fasteners shall be heat-treated and hardened with a minimum
tensile strength of 931 MPa 135,000 psi.
2.4.4
Sound Transmission Class (STC)
Enclosure panels shall have an STC of [30] [_____] dB minimum when tested
according to ASTM E 90.
2.4.5
Penetration Plates (Bolted Construction)
Plates shall be a minimum 3 mm 1/8 inch thick ASTM A 36/A 36M steel plate,
sized [450] [_____] by [450] [_____] mm [18] [_____] by [18] [_____] inches
and shall have a 6 mm 1/4 inch thick extruded brass frame for mounting to
the shielded enclosure wall panel. Penetration plates shall extend at
least 150 mm inches beyond all penetrations.
2.5
EM SHIELDED DOORS
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NOTE: Edit these paragraphs depending on type of
door used on project.
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SECTION 13095A
Page 20