USACE / NAVFAC / AFCESA / NASA UFGS-08 56 46.10 20 (April 2006)
------------------------------
Preparing Activity: NAVFAC Replacing without change
UFGS-13093N (December 2001)
UNIFIED FACILITIES GUIDE SPECIFICATIONS
References are in agreement with UMRL dated January 2009
SECTION 08 56 46.10 20
RADIO FREQUENCY SHIELDED ENCLOSURES, DEMOUNTABLE TYPE
04/06
NOTE: This guide specification covers the requirements for radio frequency
shielded enclosures, demountable Type.
Edit this guide specification for project specific requirements by adding, deleting,
or revising text. For bracketed items, choose applicable items(s) or insert
appropriate information.
Remove information and requirements not required in respective project, whether
or not brackets are present.
Comments and suggestions on this guide specification are welcome and should
be directed to the technical proponent of the specification. A listing of technical
proponents, including their organization designation and telephone number, is
on the Internet.
Recommended changes to a UFGS should be submitted as a Criteria Change Request
(CCR).
NOTE: This guide specification covers the requirements for radio frequency
shielded enclosures, demountable Type, in sizes under 50 square meter 500 square
feet. For larger enclosures and for High Altitude Electromagnetic Pulse (HEMP)
protected enclosures, contact NAVFAC Engineering Innovation and Criteria Office
(Code EICO) before beginning design. Do not design HEMP enclosures utilizing
demountable shield construction. The electrical designer should refer to MIL-HDBK-419
Volumes I and II for special grounding and bonding requirements for EMI enclosures
and to NACSIM 5203 for TEMPEST enclosures. All metallic electrical conduits
which penetrate a TEMPEST shield must be isolated within 50 mm 2 inches of the
exterior of the shield by a nonmetallic conduit section at least 150 mm 6 inches
long to prevent conduction of information from the shielded enclosure. Although
not addressed in this specification, it is recognized that fiber optic cable
has gained acceptance as an effective method of transmitting data across the
boundary of shielded enclosures without filtering. If fiber optic cable is
used, describe the penetration of the shield in detail. For a discussion of
the advantages and disadvantages of fiber optic systems see NAVFAC DM-12.02.
Designer should consult these documents and other appropriate sources before
applying this guide specification to large scale EMI enclosures to HEMP and
to TEMPEST Projects. The potential requirement for thermal expansion joints
inherent to large scale enclosures is not addressed in this guide specification.
The extent and location of the work to be accomplished and wiring, equipment,
and accessories necessary for a complete installation should be indicated on
the project drawings.
NOTE: The following information shall be shown on the project drawings:
1. Assembly details;
2. Penetration details;
3. Location and method of mounting shielded enclosure within building;
4. Location of mechanical and electrical equipment within shielded enclosure;
5. Interior wall finish;
6. Suspended ceiling; and
7. Raised computer floor.
PART 1 GENERAL
1.1 REFERENCES
NOTE: This paragraph is used to list the publications cited in the text of
the guide specification. The publications are referred to in the text by basic
designation only and listed in this paragraph by organization, designation,
date, and title.
Use the Reference Wizard's Check Reference feature when you add a RID outside
of the Section's Reference Article to automatically place the reference in the
Reference Article. Also use the Reference Wizard's Check Reference feature
to update the issue dates.
References not used in the text will automatically be deleted from this section
of the project specification when you choose to reconcile references in the
publish print process.
The publications listed below form a part of this specification to the extent referenced. The publications are
referred to within the text by the basic designation only.
[AIR MOVEMENT AND CONTROL ASSOCIATION INTERNATIONAL (AMCA)AMCA 210(2007) Laboratory Methods of Testing Fans for Aerodynamic Performance Rating][ASTM INTERNATIONAL (ASTM)ASTM A 653/A 653M(2008) Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip ProcessASTM B 194(2008) Standard Specification for Copper-Beryllium Alloy Plate, Sheet, Strip, and Rolled BarASTM E 84(2008a) Standard Test Method for Surface Burning Characteristics of Building MaterialsASTM E 90(2004) Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and ElementsASTM F 1066(2004) Standard Specification for Vinyl Composition Floor Tile][INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS (IEEE)IEEE Std 299(2006) Standard Method for Measuring the Effectiveness of Electromagnetic Shielding Enclosures][NATIONAL FIRE PROTECTION ASSOCIATION (NFPA)NFPA 70(2007; AMD 1 2008) National Electrical Code - 2008 Edition][U.S. DEPARTMENT OF COMMERCE (DOC)DOC FED PS51(1971; R 1972) Hardwood and Decorative PlywoodDOC FED PS58(1974) Basic Hardboard][U.S. DEPARTMENT OF DEFENSE (DOD)MIL-PRF-15733(Rev H; Supp 1; Am 1; Am 2; Am 3) Filters and Capacitors, Radio Frequency InterferenceMIL-STD-220(Rev B; Notice 1) Method of Insertion-Loss MeasurementMIL-STD-461(Rev F) Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment][U.S. GENERAL SERVICES ADMINISTRATION (GSA)FS A-A-50032(Rev B) Fans, Ventilating, Propeller]1.2 GENERAL REQUIREMENTS
NOTE: Insert additional details describing the specific project for which this
specification is being used. Projects involving military communications equipment
must be designed to incorporate the applicable requirements of MIL-STD-188-124,
"Grounding, Bonding and Shielding for Common Long Haul/Tactical Communication
Systems." Be aware that standard manufactured shielded doors are not designed
for exposure to weather.
Section 26 00 00.00 20 BASIC ELECTRICAL MATERIALS AND METHODS, applies to this section, with the additions and
modifications specified herein. The enclosure[s] shall be capable of being erected, disassembled, and reerected
entirely from its interior without special tools [, except where RF enclosure ceiling is specified as being supported
by the structural ceiling above]. Provide enclosure[s] complete with [power line filters,] [telephone/signal
line filters,] [RF air vents,] [penetrations for compressed air lines, water lines and _____,] [coaxial cables,]
[lighting fixtures,] [workbenches with convenience outlets,] and door assembly. Provide each item with fittings
and hardware necessary for a complete and operable RF shielded enclosure. Where two or more units of the same
type, class, and size of equipment are required, these units shall be products of a single manufacturer. Provide
means of completely isolating the structure electrically from the building in which it is to be installed.
1.2.1 Mechanical Work
NOTE: Modify or delete these paragraphs as required for each project. Additional
items such as raised computer floors may be specified in the same manner.
NOTE: Insert appropriate Section number and title in blank below using format
per UFC 1-300-02.
Provide complete shielded enclosure[s] including work specified in [_____] [and [_____]].
1.2.2 Electrical Work
NOTE: Modify or delete these paragraphs as required for each project. Additional
items such as raised computer floors may be specified in the same manner.
NOTE: Insert appropriate Section number and title in blank below using format
per UFC 1-300-02.
Conform to the requirements of the NFPA 70, National Electrical Code. Provide a complete shielded enclosure[s]
including work specified in [_____] [and [_____]].
1.2.3 Acoustical Ceiling System
NOTE: Modify or delete these paragraphs as required for each project. Additional
items such as raised computer floors may be specified in the same manner.
Provide as specified in Section 09 51 00 ACOUSTICAL CEILINGS.
1.3 SUBMITTALS
NOTE: Review submittal description (SD) definitions in Section 01 33 00 SUBMITTAL
PROCEDURES and edit the following list to reflect only the submittals required
for the project. Submittals should be kept to the minimum required for adequate
quality control.
A “G” following a submittal item indicates that the submittal requires Government
approval. Some submittals are already marked with a “G”. Only delete an existing
“G” if the submittal item is not complex and can be reviewed through the Contractor’s
Quality Control system. Only add a “G” if the submittal is sufficiently important
or complex in context of the project.
For submittals requiring Government approval on Army projects, a code of up
to three characters within the submittal tags may be used following the "G"
designation to indicate the approving authority. Codes for Army projects using
the Resident Management System (RMS) are: "AE" for Architect-Engineer; "DO"
for District Office (Engineering Division or other organization in the District
Office); "AO" for Area Office; "RO" for Resident Office; and "PO" for Project
Office. Codes following the "G" typically are not used for Navy, Air Force,
and NASA projects.
Choose the first bracketed item for Navy, Air Force and NASA projects, or choose
the second bracketed item for Army projects.
Government approval is required for submittals with a "G" designation; submittals not having a "G" designation
are [for Contractor Quality Control approval.][for information only. When used, a designation following the
"G" designation identifies the office that will review the submittal for the Government.] The following shall
be submitted in accordance with Section 01 33 00 SUBMITTAL PROCEDURES:
SD-02 Shop Drawings
Radio frequency shielded enclosure
Include penetration details.
SD-03 Product Data
Telephone and signal line filters
Shielded air vents
Lighting fixtures
Exhaust fan
Door assemblies
SD-06 Test Reports
NOTE: When specifying nonlatching doors, delete door static load and sag tests
and cycle test for door latches. Retain cycle test for door hinges.
Door static load test
Door sag test
Swinging door closure test
EMI tests for line filters
Submit final report to Resident Officer in Charge of Construction within 30 days following
completion.
Attenuation testing
Seam leak detection testing
The results of EMI testing shall be submitted to the Contracting Officer on a daily basis
and test results incorporated into a EMI Shielding Test Final Report. Submit final reports within
30 days following completion of tests. List location of the permanent SELDS test leads.
SD-07 Certificates
Performance test plan
Qualifications of installation supervision personnel
Qualifications of testing agency
Certification of test equipment
Components of shielded enclosure individually and as a system, meet specified attenuation requirements.
SD-10 Operation and Maintenance Data
Shielded enclosure, Data Package 3[; G][; G, [_____]]
Submit in accordance with Section 01 78 23 OPERATION AND MAINTENANCE DATA.
1.4 RELIABILITY
Reliability to maintain high shielding effectiveness for long term usage with minimum maintenance shall be stressed
throughout the design, construction, and erection of the specified shielded enclosure. Particular attention
shall be paid to the total project so that corrosion and the installation of electrical service, power line filters,
ventilation, and connector panels do not derate the required shielding effectiveness. The enclosures will be
subject to varying moveable live floor loads and continuous use of the ventilation system and ac power line filters.
1.5 DELIVERY AND STORAGE
Deliver materials to the job site in undamaged condition. Store material to ensure proper alignment, and protect
material against dampness and accumulated moisture before and after delivery. Store materials under cover in
a well-ventilated enclosure, and do not allow materials to be exposed to extreme changes in temperature and humidity.
Do not store materials in the building until concrete and masonry are dry.
1.6 QUALITY ASSURANCE
1.6.1 Certificates
1.6.1.1 Performance Test Plan
Submit a performance test plan for SELDS and IEEE Std 299 testing of the facility. The test plan shall include
tester qualifications, equipment listings (including calibration dates and antenna factors), and proposed test
report format. The plan shall also address specific dates and durations that testing will be conducted during
the overall construction period so that the expert Government witness may be scheduled to observe the testing
and so that repairs may be made to the shield and retests conducted before the building finish materials are
installed. Finally, the test plan shall indicate the proposed dates and duration of the lowest and the highest
frequency tests following installation of the building finish materials [so that an expert Government witness
may be available for these final acceptance tests].
1.6.1.2 Qualifications of Testing Agency
Submit the experience and qualifications of an independent testing agency for review and approval. The testing
agency shall have recent experience in Shielded Enclosure Leak Detection System (SELDS) and IEEE Std 299 shielded
enclosure testing and shall list where and when the experience was obtained. Submit with the performance test
plan.
1.6.1.3 Certification of Test Equipment
Certify that test equipment for the attenuation testing has been calibrated within last 12 months.
1.7 MAINTENANCE
1.7.1 Contents
In addition, the manual shall contain the following information:
a. A complete set of assembly and disassembly drawings;
b. A schedule of recommended maintenance and adjustment procedures to ensure continuous shielding
effectiveness;
c. Allowable loads on top of room and on shelves mounted on walls, including permissible weights
of equipment that can be mounted on walls; and
d. Prescribed method of handling panels, cleaning of seams and contact fingers, bonding jumpers,
installing metallic items penetrating the shielding material without decreasing the attenuation
characteristics.
PART 2 PRODUCTS
2.1 SHIELDED ENCLOSURE CHARACTERISTICS
2.1.1 Radio Frequency Interference Attenuation
The attenuation and shielding effectiveness requirements apply to the finished shielded enclosure[s] and enclosure's
components when all power line filters are installed and carrying current, ventilation systems are operating,
[the coaxial connector panels capped,] and shielded door[s] are in normal operation position. The specified
shielded effectiveness shall be achieved without using conductive tapes, gaskets, or cement materials. Provide
enclosure[s] having the following minimum magnetic, electric, and plane wave attenuation:
Magnetic - [60] [_____] dB at 14kHz increasing linearly to [100] [_____] dB at 200 kHz
Electric - [100] [_____] dB from 1.0 kHz to 50 MHz
Plane Wave - [100] [_____] dB between 50 MHz and 10 GHz
2.1.2 Sound Transmission Class (STC)
NOTE: STC 30 provides only minimum sound transmission loss. For greater sound
control, more detailed acoustical design requirements must be incorporated into
the specification.
Provide enclosure[s] having an STC of [30] [_____] dB minimum when tested according to ASTM E 90 [not including
sound transmission loss of surrounding building construction].
2.2 PANELS CONSTRUCTION
Flat steel sheet laminated to each side of a 20 mm 3/4 inch 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.]
2.2.1 Flat Steel Sheet
ASTM A 653/A 653M with Z180 G-60 coating, minimum 24 gage, phosphatized.
2.2.2 Plywood
DOC FED PS51 for exterior, sound grade hardwood, Type I.
2.2.3 Hardboard
DOC FED PS58 for standard type hardboard.
2.2.4 Adhesive for Laminating Steel Sheets to Structural Core
Waterproof type which maintains a permanent bond for the lifetime of the enclosure.
2.2.5 Floor Finish
NOTE: Indicate or specify whether other flooring is to be provided or higher
floor loads are required. This is most critical when raised floors are required.
Allowances must be made for elevated door thresholds. Vinyl composition 1 is
asbestos-free and should be specified for all projects.
Vinyl-composition tile, ASTM F 1066, Type IV, composition 1, 300 by 300 mm, 3 mm 12 by 12 inches, 1/8 inch, thick.
2.3 FRAMING-JOINING SYSTEM
The panels shall be joined and supported by specially designed members that clamp the edges of the panels and
provide continuous, uniform, and constant pressure contact against 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 35 kg 75 pounds applied normal 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. At corner intersections of walls, floor, or ceiling, provide a one-piece factory prewelded corner section
or trihedral corner framed with brass machined cast corner cap assemblies consisting of inner and outer parts.
The modular enclosure shall be designed for ease of erection, disassembly, and re-assembly.
2.3.1 Channels
The framing-joining system members shall consist of 3 mm 1/8 inchzinc-plated steel channels having 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.
2.3.2 Screw Fasteners
Screw fasteners shall be either zinc-plated or cadmium-plated steel, minimum size 6 mm 1/4 inch - 20 with pan
or flat Phillips heads. Fasteners shall be heat treated and hardened with minimum tensile strength of 930 MPa
135,000 psi.
2.4 DOOR ASSEMBLIES
NOTE: Do not accept doors that deviate from this specification without consulting
NAVFAC 15C. Probable deviations include: magnetic and electromagnetic doors,
other non-finger stock type doors, adhesive mounted finger stock, and requests
to approve doors tested to less than 10,000 open close cycles, among others.
The enclosure door shall be nonsagging and nonwarping and shall afford shielded effectiveness equal to the rest
of the enclosure when the door is closed. The shielded door shall be provided with [multiple rows] [at least
one row] of RF finger stock around the door or its frame. The fingers that form a contact between the door and
its frame shall be protected from damage due to physical contact and shall be concealed within the door and frame
assemblies. The door shall have a clear opening of [900 mm] [36 inches] [_____] wide and [2100 mm] [84 inch]
[_____] high. Door assembly shall be the same manufacture as the enclosure. Doors shall be reinforced steel
or laminated type. Laminated type shall be the same construction as enclosure panels, except the steel faces
shall be electrically and mechanically joined by channels or overlapping seams, both of which shall be continuously
seam welded along all joined surfaces.
2.4.1 Finger Stock
Contacts for doors shall be copper beryllium conforming to ASTM B 194, Condition HT. The finger stock shall
be secured to the door or frame without using special tools or soldering or adhesives and shall have a minimum
overlap of 50 mm 2 inches.
2.4.2 [Latching Type
NOTE: Select the applicable paragraph(s) from the following:
NOTE: Specially designed door for electrical or pneumatic operation may be
specified; however, these special doors are not compatible with all demountable
enclosures.
The door shall be lever controlled with roller cam action requiring not more than 90 N 20 pounds of operating
force on the handle for both opening and closing. The door shall be equipped with a two or three-point latching
mechanism that provides proper compressive force for the RF seal. The mechanism shall be operable from both
sides of the door and shall have permanently-lubricated ball bearings at points of pivot and rotation. The door
latches and hinges shall be rated for a minimum of 10,000 cycles without loss of attenuation and without adjustments.]
[Nonlatching Type
NOTE: Nonlatching doors may be used for enclosures having many daily open-close
operations; however, they may not retain as high an attenuation over the long
term compared with doors having three-point latching mechanisms.
The door shall be equipped with three heavy-duty ball bearing hinges and a door pull. Door shall open and close
with a force not to exceed 20 N 5 pounds.]
2.5 LINE FILTERS
2.5.1 Power Line Filters
Shall conform to the requirements of Section 26 35 46.00 20 RADIO FREQUENCY INTERFERENCE POWER LINE FILTERS and
shall have current and voltage ratings as [indicated] [specified].
2.5.2 Telephone and Signal Line Filters
MIL-PRF-15733. Filters shall have an insertion loss of 100 decibels in the frequency range of 14 kHz to 10 GHz
measured according to MIL-STD-220, full load condition. Filters shall have a pass band of [_____] kHz to [_____]
kHz with a characteristic impedance of [_____] ohms.
2.6 WAVEGUIDE-TYPE AIR VENTS
Honeycomb-type air vents shall have cores fabricated of brass or steel, and each guide shall be electrically
and mechanically bonded to all adjacent guides. Air vents shall be a permanent part of the shielded enclosure
and shall have a shielding effectiveness equal to that of the total enclosure. Static pressure drop through the
vents shall not exceed 5 Pa 0.02 inch water gage at an air velocity of 3 m/s 600 feet per minute.
2.7 GROUNDING STUD
Enclosure shall have a permanently installed, solid brass or bronze grounding stud complete with hardware and
jamb nuts located in the entrance plate [unless otherwise specified or indicated]. The stud shall be 13 mm
1/2 inch diameter double-threaded bolt which allows a full 50 mm 2 inch running thread inside and outside of
the shielded enclosure.
2.8 SERVICE ENTRANCE PLATES (SET-UP PANELS)
Shall be minimum 3 mm 1/8 inch thick steel, sized [300 by 300 mm] [12 by 12 inches] [_____] and shall have a
6 mm 1/4 inch extruded brass frame for mounting to shielded enclosure wall panel.
2.9 NAMEPLATES
Major components of equipment shall have manufacturer's name, address, catalog number, model, style, and type
on a plate securely and conspicuously attached to each item of equipment. Nameplates for electrical apparatus
shall conform to NEMA Standards.
2.10 LIGHTING
NOTE: In shielded enclosures where electronic equipment is very sensitive to
EMI, specify a dual lighting system so that fluorescent lighting can be turned
off and incandescent lighting left on during sensitive tests or operations.
Provide lighting fixtures as indicated [and as specified in Section 26 51 00 INTERIOR LIGHTING]. Fluorescent
lighting fixtures shall meet the requirements of MIL-STD-461, Class C3, Group I for both conducted and radiated
interference.
2.11 EXHAUST FAN
NOTE: This paragraph cites only minimum requirements. Design calculations
are necessary to size HVAC to suit room size and equipment/personnel contained
within. Exhaust fan motors located inside shielded enclosure must meet MIL-STD-461,
Class C3, Group I.
FS A-A-50032, Type I, Class 1 for direct drive, Class 2 for belt drive, Style A for wall or window mounting,
Style B for roof or ceiling mounting, except that fans shall be centrifugal type with aluminum housing and wheel.
Additionally exhaust fans shall meet the electromagnetic compatibility requirements of FS A-A-50032. Motors
shall be completely shielded from the air stream. Provide exhaust opening and gravity closing type automatic
louvers. Provide exhaust which can supply 15 room air changes per hour. Capacity of fans shall be certified
in accordance with AMCA 210, and shall be not greater than 110 percent of the indicated capacity at indicated
pressure drop.
2.12 COAXIAL CABLE PENETRATIONS
For each coaxial cable entering the shielded enclosure, provide RF waveguide threaded insert with cap and chain
on shielded room side of enclosure.
2.13 SOURCE QUALITY CONTROL
NOTE: When specifying nonlatching doors, delete door static load and sag tests
and cycle test for door latches. Retain cycle test for door hinges.
2.13.1 Door Static Load Test
The door shall be mounted and latched to its frame, then set down in a horizontal position such that the door
will open downward and only the frame is rigidly and continuously supported from the bottom. A load of 2kPa
40 psf shall be applied uniformly over the entire surface of the door for at least 10 minutes. The door will
not be considered acceptable if this load causes breakage, failure, or permanent deformation which varies the
clearance between door leaf and stops to vary more than 2 mm 1/16 inch from the original dimension.
2.13.2 Door Sag Test
The door and its frame shall be installed normally and opened 90 degrees. Two 23 kg 50 pound weights, one on
each side of the door, shall be suspended from the door within 125 mm 5 inches of the outer edge for at least
10 minutes. The door will not be considered acceptable if this test causes breakage, failure, or permanent deformation
which varies the clearance between the door leaf and floor frame more than 2 mm 1/16 inch from its original dimension.
2.13.3 Swinging Door Closure Test
Door shall be operated 5000 complete open-close cycles. The door will not be acceptable if the closure test
causes any breakage, failure, or permanent deformation that causes the clearance between door and frame to vary
more than 2 mm 1/16 inch from the original dimension.
PART 3 EXECUTION
3.1 INSTALLATION
3.1.1 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 hours 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.
3.1.2 Panel Installation
Lay panels in a straight line with true, level, and even surfaces and with the joints in alignment; install them
in accordance with the shielding manufacturer's recommendations. Exercise care while handling and installing
metal shielding panels to ensure that panels are not damaged. Clean exposed surfaces of all 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 RF panels with 16 mm 5/8 inch long,
zinc-plated, self-tapping screws. Keep electrical conduits as close to RF shielding as possible. Do not use
framing-joining system bolts to mount material and equipment. If material and equipment penetrate shielded enclosure,
seam weld or solder materials and equipment to both shielding surfaces.
3.1.3 Surface Preparation
Clean and buff surfaces to ensure good electrical contact with shielding surface. 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.
3.1.4 Floor Panel Setting
Place a polyethylene film of 6-mil thickness over the structural floor of the parent room before any other work
is set thereon. Provide a 3 mm 1/8 inch thick layer of hardboard over this film with joints loosely butted.
Over this layer provide an additional layer of similar filler material of equal thickness as the projection of
the framing-joining member from the bottom surface of the floor panel leaving no more than 6 mm 1/4 inch space
between the hardboard and the framing-joining member.
3.2 FRAMING-JOINING SYSTEM
Tighten screws with a calibrated adjustable torque wrench so that equal torque can be set on each screw. (Proper
torque values will be approximately 9 Nm 80 inch pounds, but may vary somewhat depending on the manufacturer).
3.3 DOOR ASSEMBLIES
Mount so that the clearance between the door edges and frame shall not vary more than 2 mm 1/16 inch and the
innerface of the door periphery does not vary more than 2 mm 1/16 inch from the plane of the face of the stop.
Through-bolt hinges to the door and the frame.
3.4 LINE FILTERS
Provide filters for incoming electrical power lines [, including neutrals,] and for incoming telephone and signal
lines. Support filters independently of the shielding.
3.5 WAVEGUIDE-TYPE AIR VENTS
[Provide each inlet and return air duct with the number and size of waveguide-type air vents at each location
where the ducts enter the shielded enclosure.] [As a minimum, provide each enclosure with one 300 mm 12 inch
square and one 300 mm 12 inch square return waveguide-type air vent.]
3.6 EXHAUST FAN
Mount on [wall] [or] [ceiling] over the exhaust vent on the exterior surface of shielded enclosure. Provide
power from electrical source exterior to the shielded enclosure.
3.7 CONDUCTOR INSTALLATION
Provide filtered conductors in conduit, except for coaxial cables, from filter to shielding and penetrate the
enclosure through threaded rigid steel conduits. [Twist conductors leading from the filters and conductors inside
the shielded enclosure approximately 10 turns per foot in the conduit.]
3.8 GROUNDING
NOTE: If not specified in Division 16, "Electrical," the following sentence
shall be added: "Wires inside the enclosure and for a distance of at least 15
meters 50 feet outside of the enclosure shall be enclosed in a grounded, threaded
rigid steel conduit system."
Extend the grounding stud through and [bolt] [weld] it to the electrical power panel with a minimum No. 4 AWG
insulated stranded copper conductor to effectively serve as a single grounding point for the completely assembled
shielded enclosure, both internally and externally.
3.9 SERVICE ENTRANCE PLATE
Install RF connectors for coaxial cable and other RF shielded cable on entrance plate. Soft solder connectors
to the plate. If location of plate is not indicated, mount plate in wall panel adjacent to power line filters.
3.10 FIELD TESTS
3.10.1 Seam Leak Detection Testing
NOTE: SELDS testing the seams in the floor shielding is usually very difficult
because you cannot "sniff" on both sides (assuming the shield is on the ground
level). To circumvent this problem SELDS loops may be positioned beneath the
floor shield for SELDS testing.
Continuously test seams during fabrication using the SELDS, commonly known as a "sniffer." Upon completion of
the basic shielded enclosure, before applying any metal primer or installing any accessories, test the entire
shielded enclosure with the SELDS. Install terminal points on the shielding exterior and permanently attach
test leads on two sets of diagonally opposing corners during construction for use with the SELDS. Continuously
probe seams with the test receiver set to detect abrupt change of shielding level greater than 10 dB on the "shielding
unit" scale. Clearly mark points having change greater than 10 dB and repair the seam to meet the specified requirement.
Retest each repaired point until there are no points on seams which fail test.
3.10.2 Attenuation Testing
[Furnish the services of an independent testing laboratory, approved by the Contracting Officer, to test the
shielded enclosure. Certify that laboratory is equipped and staffed to perform field tests of RF shielded enclosures
and performs the tests as a normal service.] [Final acceptance testing will be by the Government.] Conduct
the final shielding acceptance test after penetrations have been completed, specifically including electrical
and other utility penetrations. In addition, the Contractor may schedule a complete or abbreviated test to verify
that the shielding assembly is adequate prior to conducting final shielding acceptance test.
3.10.2.1 Test Method
NOTE: Expert Government witness should be present for all final acceptance
testing. Note that IEEE Std 299 requires one magnetic field test (150 kHz),
three electric field tests (200 kHz, 1 MHz, 18 MHz), and one plane wave test
(400 MHz). Also, note that IEEE Std 299 and NSA 65-6 differ on positioning
of source and receiver. IEEE Std 299 requires source outside and receiver
inside the shield, while NSA 65-6 requires source inside and receiver outside
(to simulate TEMPEST conditions). For TEMPEST shielding effectiveness testing,
continuous sweeping of seams at one or more plane wave frequencies should also
be specified, in addition to testing around all door panels, filters, air duct
penetrations and all other penetrations of the shielding at all test frequencies.
If enclosure is designed specifically for attenuating microwave frequencies,
specify additional test frequencies above 1 GHz. Such testing is expensive
and should only be used when a firm requirement exists (e.g., NSA-65-6).
The test procedure, frequencies, and equipment shall be as specified in IEEE Std 299 [plus the additional frequencies
specified in the contract]. Perform the test as soon as possible after completion of the shielded enclosure,
including installation of services, power/telephone/signal lines, RF filters, and waveguide vents. Conduct tests
with doors closed and the filters under normal load conditions.
3.10.2.2 Additional Test Points
NOTE: Use this paragraph if design includes strict tolerances, high attenuation
requirements, and many penetrations.
Measure additional test points beyond those specified in IEEE Std 299. Test points include the periphery of doors
and covers, handles, latches, power filter penetrations, air vent filters, telephone and control line filter
penetrations, and points of penetration by pipes, tubes, and bolts.
3.10.3 Final In Service Testing
Upon completion of acceptance checks, settings, and tests, show by demonstration in service that equipment and
devices are in operating condition and performing the intended function. Give the Contracting Officer five working
days advance notice of the dates and times for checks and tests.