3.7.4
Shielded Enclosure Leak Detection System (SELDS) Testing
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NOTE: SELDS testing the welds in the floor
shielding is usually performed on the interior only
because it is not possible to "sniff" on both sides
(assuming the shield is on the ground level). Dye
penetrant may also be used to test the welds where
SELDS testing is not possible. The SELDS can be
obtained commercially from the following: 1.
Carnel Labs Corporation 21434 Osborne Street Canoga
Park, CA 91304 Telephone: (818) 882-3977 2.
Rayproof Shielding Systems Corporation 50 Keeler
Avenue Norwalk, CT 06854 Telephone: (203) 838-4555
3. Retlif Corporation 795 Marconi Avenue
Ronkonkoma, NY 11779 Telephone: (516) 737-1500
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The leak detection system shall use a 95- to 105-kHz oscillator and a
battery operated hand-held receiver. The receiver or "sniffer" shall have
a ferrite loop probe capable of sensing leaks within 6 mm 1/4 inch of the
probe location with a dynamic range of 140 dB. Testing shall be conducted
in accordance with test equipment manufacturer's instructions. Test loops
or leads shall be placed under the shield floor or into inaccessible
locations prior to installation to assist in the detection of seam leaks in
the floor, ceiling and walls. The loop or lead wires shall be placed
between the vapor barrier and the structural slab for the floor shield with
the leads brought to an accessible location. The test leads shall be
insulated stranded copper conductors 2 to 2.5 mm 5/64 to 3/32 inch diameter
and bonded to the shield only at the end. Test leads shall be placed in
plastic conduit for protection and shall not exceed 45 m 150 ft in length.
The surface area of the shield will determine the number of test leads
(drive points) that are required. Drive points shall be installed on the
shielding exterior and attached to two sets of diagonally opposing corners
during construction. The distance between test lead connections on a
shield surface shall not be more than 20 m 66 ft. The maximum testing area
shall be 400 sm 4300 sf. If the shield area exceeds this requirement,
additional drive points shall be provided. Bonding of the test leads to
the shield is accomplished by brazing or high-temperature soldering. Test
leads from the drive points shall be run to a lockable test cabinet for
connection to the SELDS oscillator. If more than one test cabinet is
required for a given area or building, test leads that would be common to
different surface areas shall be duplicated at each test cabinet to ensure
that test point parings are maintained. The Contractor shall record the
location of the permanent test leads and shall provide this information to
the Contracting Officer for permanent reference. Welds and seams shall be
100 percent tested. Seams shall be continuously probed with the test
receiver set to detect abrupt changes of shielding level greater than 10 dB
on the shielding unit scale. Points having a change greater than 10 dB
shall be clearly marked and shall have the weld repaired to meet the
specified requirement. Each repaired point shall be retested until there
are no points on seams which fail the test.
3.7.5
EM Shielding Effectiveness Testing
Services of an EM shielding testing specialist, approved by the Contracting
Officer, shall be furnished to test the shielded enclosure. The laboratory
shall be equipped and staffed to perform field tests of EM shielded
enclosures and shall perform these tests as a normal service. Test
SECTION 13095A
Page 53
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