2.6.3.3
Access Doors
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NOTE: Determine whether an electrical push-button
to stop the fan by a person inside the casing is
required. If required, check the drawings to ensure
that the item is shown, and properly coordinated
with electrical drawings. Push-button station will
be used for Army and Air Force projects only.
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Provide access doors in each section of the casing. Weld doorframes in
place, gasket each door with neoprene, hinge with minimum of two brass
hinges, and fasten with a minimum of two brass tension fasteners operable
from inside and outside of the casing. Where possible, doors shall be 900
x 450 mm 36 x 18 inches located 450 mm 18 inches above the floor. Where
the space available will not accommodate doors of this size, use doors as
large as the space will accommodate. Doors shall swing so that fan suction
or pressure holds door in closed position, and shall be airtight. Provide
a push-button station, located inside the casing, to stop the supply.
2.6.3.4
Factory-Fabricated Insulated Sheet Metal Panels
Factory-fabricated components may be used for field-assembled units,
provided all requirements specified for field-fabricated plenums and
casings are met. Panels shall be of modular design, pretested for
structural strength, thermal control, condensation control, and acoustical
control. Panel joints shall be sealed and insulated access doors shall be
provided and gasketed to prevent air leakage. Panel construction shall be
not less than one mm 20 gauge galvanized sheet steel and shall be assembled
with fasteners treated against corrosion. Standard length panels shall
deflect not more than 13 mm 1/2 inch under operation. Details of
construction, including joint sealing, not specifically covered shall be as
indicated in SMACNA HVAC Duct Const Stds. Construct the plenums and
casings to withstand the specified internal pressure of the air systems.
2.6.3.5
Duct Liner
Unless otherwise specified, duct liner shall conform to ASTM C 1071, Type I
or II.
2.6.4
Sound Attenuation Equipment
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NOTE: Use sound attenuators or acoustical duct
liner only where acoustical treatment is required
and there are no other suitable alternatives. Do
not use acoustical duct liner in medical facilities.
Refer to UFC 3-450-02, Noise and Vibration, for
noise criteria. Sound power levels required should
be included in the appropriate schedule on the
drawings.
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a. For systems with total pressure above 1 kPa 4 Inches Water Gauge:
Provide sound attenuators on the discharge duct of each fan operating
at a total pressure above 1 kPa 4 inch water gauge, and, when
indicated, at the intake of each fan system. Sound attenuators shall
SECTION 15895
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