N66604-19-Q-1034_-_RF_Chamber_Specifications.pdf

ACOUSTIC-RF CHAMBER SPECIFICATIONS

These specifications describe the minimum acceptable quality and/or performance level requirements of the equipment being purchased. The contractor shall fabricate and install an Acoustic Electromagnetic Interference (EMI) Chamber with Shielded Antechamber in accordance with the following specifications:

1. General Specifications

An Acoustic EMI Chamber with Shielded Antechamber shall be installed at the Naval Undersea Warfare Center Division Newport. The building and room number will be provided in the contract.

All construction material shall be new and delivered to the job site in undamaged condition.

Material shall be stored to ensure proper alignment and to protect material against dampness and accumulated moisture before and after delivery. Defective or damaged materials shall be replaced by the Contractor at no additional cost to the Government.

2. Physical Specifications

2.1-Location and Dimensions of chambers

The Shielded Antechamber shall be installed at a distance of 3-6 inches away from the support column in Room 1 (see Figure 1). The Acoustic EMI Chamber shall be installed at a distance of 3-6 inches away from the column and wall between two rooms (identified as Room 1* and Room 2*). (Note: The distance between the antechamber and the wall between Room 1 and Room 2 will be greater than 6 inches due to the column.)

*Not actual room numbers. Actual building and room numbers will be provided in the contract.

Figure 1 - Acoustic EMI Chamber with Shielded Antechamber Location

The Acoustic EMI Chamber shall have 16 feet long x 16 feet wide x 12 feet high interior dimensions (pre-finished, sheet metal to sheet metal—aka prior to the installation of the RF absorbers). The exterior dimensions shall not exceed 17 feet long x 17 feet wide x 13 feet high.

The Shielded Antechamber shall have 8 feet long x 10 feet wide x 12 feet high interior dimensions (pre-finished, sheet metal to sheet metal note: the antechamber will not have RF absorbers). The exterior dimensions shall not exceed 9 feet long x 11 feet wide x 13 feet high.

2.2-Framing and Construction

Fabreeka pad, or equivalent pad, meeting the specifications in MIL-C-882 and MIL-E-5272 shall be installed between the existing floor in Room 2 and the Acoustic EMI Chamber with Shielded Antechamber to isolate vibration and reduce noise. The Fabreeka pad, or equivalent pad, thickness shall be approved by the Government prior to installation. The Fabreeka pad, or equivalent pad, shall be trimmed where needed to avoid pinch points. The Fabreeka pad, or equivalent pad, shall be protected from damage due to welding.

The Acoustic EMI Chamber with Shielded Antechamber shall have a welded steel frame construction, in accordance with International Building Code (IBC), Chapter 16, as modified by UFC 3-301-01.

The Chamber’s and Antechamber’s shielding panels material shall meet the specifications of ASTM A1008 or ASTM A568/A568M-17A steel. The panels shall have a minimum thickness of 14 gauge. The Acoustic EMI Chamber and Shielded Antechamber shall have a continuous welded seam construction and shall be field-welded. The Acoustic EMI Chamber and Shielded Antechamber shall be welded to each other.

2.3-Welding

All welding shall be performed in accordance with the latest edition of the AWS D1.1 Structural Welding Code-Steel and AWS D1.3 Structural Welding Code- Sheet Steel. All welded surfaces shall be flat and level.

Structurally weld the shielding steel to the steel frame 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 sheets to framework at 12 inches on center to support steel sheets, then use continuous seam welding to seal RF seams in the chamber.

Welded seams shall be free of slag inclusions, gas pockets, voids, or incomplete fusion anywhere along the seams.

In-process weld testing shall be conducted. Completed welds shall be inspected by the contractor after the welds have been thoroughly cleaned by hand or power wire-brush.

Welds shall be inspected by the contractor with magnifiers under bright light for surface cracking, porosity, slag inclusion, excessive roughness, unfilled craters, gas pockets, undercuts, overlaps, size, and insufficient throat and concavity.

Weld failures shall be corrected by grinding out such welds and replacing with new welds.

2.4-Finished flooring

The Acoustic EMI Chamber and Shielded Antechamber shall have a floor installed on Fabcel 25 pad, six layers, or equivalent pad. The Fabcel, or equivalent pad, shall be placed over the metal flooring and shall abut the interior walls. The finished floor, placed on top of the Fabcel 25 pad, shall consist of ¾ inches minimum thickness plywood (treated fire retardant plywood) with a vinyl surface covering. The edge of the plywood floor shall be between ¾ inches – 1 inch away from all the walls. The gap between the finished flooring and the walls shall be filled with flexible filler rubber material. Specific material detail is not necessary with the exception of it cannot have excessive expansion nor contraction characteristics due to heat. The bottom of the Acoustic EMI Chamber and Shielded Antechamber doors shall not extend below the top of the finished floor.

2.5-Connector Access Panels

The Acoustic EMI Chamber and Shielded Antechamber shall have four (4) access apertures as follows and in accordance with Figure 1:

One (1) access aperture shall have a clear opening 24 inches wide x 12 inches high and shall interface between the Acoustic EMI Chamber and the Shielded Antechamber.

One (1) access aperture shall have a clear opening 24 inches wide x 12 inches high and shall interface between the Acoustic EMI Chamber and Room 1.

One (1) access aperture shall have a clear opening 8 inches wide x 8 inches high and shall interface between the Acoustic EMI Chamber and Room 1.

One (1) access aperture shall have a clear opening 8 inches wide x 8 inches high and shall interface between the Shielded Antechamber and Room 1.

Both of the 24 inches wide x 12 inches high access apertures shall have identical bolt pattern such that the access panels can be interchangeable between both locations. Both of the 8 inches wide x 8 inches high access apertures shall have identical bolt pattern such that the access panels can be interchangeable between both locations. The center of all four (4) access panels shall be 24 inches from the floor. All access aperture’s edges shall be ground smooth. Two (2) blanking panels shall be provided per each access aperture. All four (4) access apertures shall afford RF shielded effectiveness equal to the rest of the chamber when covered with bolt-on panels.

2.6-Doors

The Acoustic EMI Chamber and the Shielded Antechamber shall each have one (1) door that meets the specifications below:

The doors shall not warp or sag and shall afford shielded effectiveness equal to the rest of the chamber when closed.

The doors shall have a clear opening of 42 inches wide and 84 inches high.

The doors shall be reinforced steel or laminated type. Laminated type shall be the same construction as the chamber’s shielding 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.

The door assembly shall be designed to function properly throughout a minimum of 100,000 cycles and 22-years without the shielding effectiveness decreasing below the overall shield required attenuation.

The doors shall be installed with a minimum of two (2) rows of double-sided RF finger stock around the door or its frame to meet the performance specifications of Section 5. 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. Contact 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.

2.7-Grounding

The Acoustic EMI Chamber with Shielded Antechamber shall be grounded as below:

2.7.1-Exterior grounding

The Acoustic EMI Chamber shall be grounded to the Shielded Antechamber by means of the continuous welded seams between them.

The Shielded Antechamber shall be grounded to the existing Room 1 underground grounding system using a grounding lug as shown in Figure 2, and located as shown in Figure 3.

Figure 2 - Grounding Stud for Shielded Antechamber

Figure 3 - Ground Location

2.7.2-Interior grounding

The Acoustic EMI Chamber with Shielded Antechamber shall have a solid copper ground bus bar along the inside walls at a height of 42 inches off the floor and a distance of 2.5 inches from the wall. Copper ground bus bars shall have its minimum diameter 5/16 inch studs welded to the wall at distances no greater than every two (2) feet. Copper ground bus bar shall be minimum 1.25 inches x .25 inches thick.

The DC resistance between the existing underground grounding system and the copper ground bus bar inside the Acoustic EMI Chamber shall be no greater than 0.0001 Ohms.

3. Ancillary Equipment

3.1. - RF Absorber

The Acoustic EMI Chamber’s interior walls and ceiling shall be partially covered with EM absorber and ferrite tile, as shown in Figure 4 and Figure 5. The absorber material shall be in accordance with MIL-STD-461G, Section 4.3.2.1. The absorber and framing shall not extend more than 4.75 inches from the interior walls of the Acoustic EMI Chamber.

3.2. - Sound Pad

The Acoustic EMI Chamber’s interior walls and ceiling shall be partially covered in sound pad material, as shown in Figure 4. The sound pads or Acoustic-Board Ultra – Soundproofing Backer, or its equivalent, shall meet the Sound Transmission Class (STC) requirements of ASTM E90-04, ASTM E4413-04 STC = 15, and the thickness shall be no less than a 0.50-inch-thick or as approved by the Government.

Figure 4 - Acoustic EMI Chamber’s Coverage Area Top View

Figure 5 - Acoustic EMI Chamber’s Coverage Area

3.3. - Air Vents

Honeycomb-type air vents shall be installed and 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 Acoustic EMI Chamber and Shielded Antechamber and shall have a shielding effectiveness equal to that of the total chamber. At a minimum, provide two 14-inch square supply and one 14-inch square return waveguide-type air vents.

3.4. - Power Requirements

The Acoustic EMI Chamber shall have power filters installed to accommodate the following:

440VAC, 60Hz, 3-phase, 3-wire, delta power (One 100Amp circuit) 115VAC, 60Hz, 3-phase, 3-wire, delta power (One 50Amp circuit) 115VAC, 60Hz, single phase, 2-wire, delta power (Three 20Amp circuits)

The Shielded Antechamber shall have power filters installed to accommodate the following:

115VAC, 60Hz, single phase, 2-wire, delta power (Two 20Amp circuit)

3.4.1. - Power filters:

Design filters to reduce conducted RF energy in electric power lines according to MIL- PRF-15733J, and UL 1283 for facility type power line filters. Insertion loss between load side of filter and power supply side shall be not less than 100 dB at 14 kHz to 10 GHz.

Each filter unit shall be capable of being mounted individually and shall include one filter for each phase conductor of the power line and the neutral conductor. Load terminal and power input compartments shall have no knockouts, and each compartment shall have one threaded conduit hub. Seam weld hubs in place, and size and locate hubs as required for conduits indicated. Overload requirements shall be in accordance with MIL-PRF- 15733J. Provide pass band suitable for use with 60 Hz power source. Total harmonics generated by the insertion of a power line filter shall not increase line voltage distortion by more than 2.5 percent with a unity power factor load.

Perform insertion loss measurements using procedures defined in MIL-STD-220C.

Power receptacles shall be installed in a power raceway along the interior walls of the Acoustic EMI Chamber and Shielded Antechamber. The power filters shall be connected to the labelled power receptacles inside the Acoustic EMI Chamber and Shielded Antechamber. Power receptacles shall be evenly distributed throughout the Acoustic EMI Chamber and Shielded Antechamber. Power receptacle quantities shall be as many as permitted per NFPA 70 standard. The receptacles shall be installed as low as possible, as permitted per NFPA 70 standard. The bottom of the power receptacle raceway shall be 4-5 inches above the floor.

Power for the receptacles inside the Acoustic EMI Chamber shall be provided from the contractor installed power filters located over the Acoustic EMI Chamber. Power for the receptacles inside the Shielded Antechamber shall be provided from the contractor installed power filters located over the Shielded Antechamber.

3.4.2. - Lighting

Permanent lighting sources shall be installed in the interior of the Acoustic EMI Chamber and Shielded Antechamber. All lighting shall comply with OSHA regulations 1926.26 and 1915.82. Lighting fixtures shall meet the requirements of MIL-STD-461 for both conducted and radiated interference.

Power for the light fixture inside the Acoustic EMI Chamber shall be provided from the power filters located over the Acoustic EMI Chamber. Power for the light fixture inside the Shielded Antechamber shall be provided from the power filters located over the Shielded Antechamber.

4. Fire Protection

4.1. - Fire Alarm

Install two (2) fire alarm system filters. Fire alarm system filters shall meet the specifications of MIL-PRF-15733J. 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 14 kHz to 10 GHz with a characteristic impedance of 600 ohms.

4.2. - Sprinkler System

A water sprinkler system shall be installed in the Acoustic EMI Chamber and the Shielded Antechamber. The water sprinkler system shall meet the specifications of NFPA 13, as modified by UFC 3-600-01.

5. Performance Specifications

The RF shielding effectiveness performance requirements apply to the finished Acoustic EMI Chamber and Shielded Antechamber when all power line filters are installed and carrying current, ventilation systems are operating, the connector access panels are capped, lighting, and shielded door are in normal operation position. The specified shielding effectiveness shall be achieved without using conductive tapes, gaskets, or cement materials. Acoustic EMI Chamber and Shielded Antechamber shall, at a minimum, have the following magnetic, electric, and plane wave attenuation using the measurement procedures per IEEE-STD-299-2006:

Magnetic Field: 42 dB @ 60Hz increasing linearly to 120 dB @ 14kHz. 120dB from 14kHz to 1MHz.

Electric Field: 120dB from 1kHz to 18GHz.

Plane Wave: 120dB from 1MHz to 18GHz.

6. Testing

The contractor shall conduct performance testing and ensure the fabricated and installed Acoustic EMI Chamber with Shielded Antechamber meets the performance criteria stated in Section 5.