penetrations shall be sealed with full penetration circumferential EM welds.
3.2.3
Placement of Floor Shield
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NOTE: The shingle overlap method is one successful
method of floor shield placement. Designers have
the option to select other methods.
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Placement of the floor shield shall not begin until at least 14 days after
the pouring of the floor slab and Contracting Officer approval of all
required submittals. [The placement of the floor shield shall utilize [the
shingle overlap method] [_____].] [Individual floor sheet shall be
attached on the top and one side only with air-pressure drive tools to the
floor. Floor shielding sheets shall be overlapped 50 mm 2 inches at
joints, bent and laid flat on the concrete floor without voids or gaps, and
sealed with continuous EM welds at all seams and joints.] The floor shield
installation shall start at the center of the space.
3.2.4
Placement of Overslab
Before placement of the overslab over any portion of the floor shield, the
Contracting Officer's approval is required. Both visual and SELDS testing
of the shielding within the area to be covered shall be successfully
completed, any defects repaired and retested, and full test results
supplied to the Contracting Officer prior to placement of the overslab. A
vapor barrier shall be placed over the floor shield.
3.2.5
Welding
The shielding work shall be provided in accordance with the performance
criteria specified. Shielding steel structurally welded to the steel frame
shall be welded in accordance with AWS D1.1/D1.1M and AWS D1.3. EM
shielding seams shall be sealed EM-tight by the MIG method, using
electrodes structurally and electrically compatible with the adjacent steel
sheets. [Sheet steel shall be welded to support steel by plug or tack
welding at 300 mm 12 inches on center, and then sheet seams shall be
continuously EM welded to seal the enclosure] [_____]. Slag inclusions,
gas pockets, voids, or incomplete fusion will not be allowed anywhere along
welded seams. Weld failures shall be corrected by grinding out such welds
and replacing with new welds. A qualified welder shall perform welding,
both structural and EM sealing. Weldments critical to shielding
effectiveness are shown on the drawings and shall be performed in the
manner shown on the drawings. Where both structural integrity and
shielding quality are required for a given weldment, both criteria shall be
met simultaneously. Brazing shall conform to the documents discussed
above, where practical, and shall also conform to requirement of AWS BRH.
Structural, mechanical, or electrical systems penetrations shall be sealed
by providing a continuous solid perimeter weld, or braze to the shield as
specified. All shield joints and seams shall have a minimum 50 mm 2 inch
overlap and shall be sealed with a continuous solid weld. After testing,
the Contracting Officer will inspect and approve the installation prior to
covering by other trades.
3.2.6
Wall Shielding Attachment
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NOTE: The wall attachment method outlined in this
SECTION 13095A
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