PART 3
EXECUTION
3.1
SHIELDING STEEL INSTALLATION
Install in strict accordance with the shielding manufacturer's/fabricator's
recommendations. Exercise care while handling and installing shielding
steel to ensure against damage. Clean exposed surfaces of dirt, finger
marks, and foreign matter resulting from manufacturing processes, handling,
or installation. Inside the enclosure, mount items including boxes,
conduits, fixtures, and switches directly to the structural steel members.
Do not allow mounting bolts and screws to penetrate shielding steel. Locate
electrical conduits as close to RF shielding as possible. If materials and
equipment penetrate the shielded enclosure, seam weld or solder materials
and equipment to both surfaces or shielding steel. Where the steel sheet
is much thinner than the penetrating member, provide a welded collar of
intermediate thickness for transition to accomplish the welding.
3.1.1
Surface Preparation
Clean and buff surfaces to ensure firm contact with shielding steel. Remove
paint or other coverings on mating surfaces of special boxes such as for
fire alarm systems, buzzers, and signal lights, including areas between box
and cover, box and wall, and box and conduit. Remove insulating material
to maintain a low-resistance ground system and to ensure firm mating of
metal surfaces.
3.1.2
Installation Supervision
Furnish the services of a qualified installation engineer or technician
regularly employed by the shielding manufacturer/fabricator for a minimum
of three 8 hour working days to instruct Contractor personnel in the
installation of the RFI shield. A qualified installation technician is
acceptable in lieu of a qualified installation engineer. After the
shielded enclosure has been completely installed including RF filters,
vents, and exhaust fans, furnish the services of the engineer or technician
described herein to inspect the installation for compliance with the
specifications. The inspection shall be made before any finishes or the
concrete topping coat are installed.
3.1.3
Floor Panel Setting
Place a polyethylene dielectric film of 0.15 mm 6 mil thickness over the
structural floor of the parent enclosure before any other work is set
thereon. Provide a 3 mm 1/8 inch thick layer of hardboard over the film,
with joints loosely butted. Over hardboard layer, provide an additional
layer of similar filler material of equal thickness as the projection of
the structural member from the bottom surface of the floor panel, leaving
no more than 6 mm 1/4 inch space between the hardboard and the structural
member. Along panel seams and at support channels, provide a refractory
glass cloth strip to protect subfloor and dielectric film from welding heat.
3.1.4
Welding
Provide the electromagnetic shielding work in accordance with performance
criteria specified. Structurally weld the shielding steel to the steel
frame in accordance with AWS D1.1/D1.1M, and seal electrical seams RF tight
by the MIG method, using electrodes structurally and electrically
compatible with the adjacent steel sheets. Plug weld or tack weld steel
sheet to framework at 300 mm 12 inches on center to support steel sheets,
SECTION 13094N
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