rubber air seal are fitted and can be easily removed and replaced without
the use of special tools and without the application of solders. The door
shall mate to the frame in a manner that allows the insertion of a brass
knife edge between the two rows of the radio frequency finger stock, to
obtain optimum conductivity and electromagnetic shielding.
High-temperature silver solder shall be used to attach the brass knife edge
components to the door panels and the 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
assembly.
2.5.3
Pneumatic Sealing Doors
Pneumatic sealing mechanisms shall achieve EM shielding by using pressure
to force the door panel against the frame surface. Contact areas of door
and frame shall be a peripheral strip not less than 75 mm 3 inches wide
completely around the door with a tinned or highly conductive noncorrosive
surface. After the door is in a closed position, the pneumatic sealing
mechanism shall exert pressure in not more than 10 seconds. The sealing
mechanism release shall be actuated in not more than 5 seconds. Manual
[override] [operation] shall not exceed a maximum of [155] [_____] N [35]
[_____] pounds. When the door is sealed, the attenuation around the edges
shall meet the EM shielding effectiveness requirements of this
specification. Swinging doors shall have a threshold of zinc-plated steel,
not less than 9.5 mm 3/8 inch thick. The door shall be provided with a
pneumatic system that maintains a nominal sealing pressure of [240] [_____]
kPa [35] [_____] psi. A label shall be attached to pneumatic doors warning
against painting of the mating surfaces.
2.5.3.1
Door and Enclosure Design
Doors shall be designed for long life and reliability without the use of EM
gaskets, EM finger stock, or other sealing devices other than the direct
metal-to-metal contact specified. The EM sealing device shall be fail-safe
upon loss of air pressure and shall readily allow manual opening of the
door. For either normal or fail-safe operation, the maximum time to reach
the open position shall be no more than 7 seconds. The enclosure design
shall include provision for removing the door for routine maintenance
without disturbing its alignment and EM sealing properties.
2.5.3.2
Control Panel
The inside and outside of the shielded enclosure shall contain a control
panel including the necessary opening and closing pneumatic valves. The
outside control panel shall also have a pressure regulator and filter. The
door air supply shall be capable of quick opening from inside the enclosure
to allow escape when opening pneumatic valves fail or malfunction.
2.5.3.3
Air System for Pneumatic Sealing
A complete air system including compressor, filter alarm, tank, lines, air
filter, dryer, air control valves, and controls shall be provided. Air
tank capacity shall be sized so that the air volume and pressure are
sufficient to operate the door through ten complete cycles after the loss
of normal power.
2.5.4
Magnetic Sealed Door Type
An EM seal shall be formed by a solid metal-to-metal contact around the
SECTION 13095A
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