and the specified diffusers.
2.4.2.1
Air Supply Riser Assembly
**************************************************************************
NOTE: Include this paragraph if distribution system
is mounted on a T-wall.
**************************************************************************
An air supply riser assembly shall be provided for each removable header to
connect the drop leg to the air main. The riser assembly shall consist of
a vertical pipe projecting from the air main through a floor sleeve cast in
the concrete T-wall, an elbow, a butterfly valve between the elbow and the
drop leg, and required supports and anchors.
2.4.2.2
Air Supply Lateral Assembly
**************************************************************************
NOTE: Include this paragraph if distribution system
is mounted on a Y-wall.
**************************************************************************
An air supply lateral assembly shall be provided for each removable header
to connect the drop leg to the air main. The lateral assembly shall
consist of piping, a butterfly valve, and required supports and anchors.
2.4.2.3
Removable Header Assembly
The removable header assembly shall consist of a drop leg and a header.
The upper end of the header assembly shall be a 90 degree elbow with face
ring and neoprene gasket for connection to the air supply assembly. The
connection to the air supply assembly shall be a quick coupling flange.
The lower end of the drop leg shall be flanged for connection to the
header. Headers shall have welded end caps and a beveled flange for
connection to the drop leg. Diffuser connectors shall be provided for
field installation of diffusers. The removable header assembly shall be
designed to withstand a vertical load that results in a moment of 56.5 N m
500 inch-pounds at the diffuser connection without permanent deformation.
Lifting lugs shall be provided on the assembly as required for removal of
the header. Removable header assembly shall be stainless steel systems or
galvanized steel systems as follows:
a.
Stainless Steel Systems: The removable header assembly shall be
fabricated from 304L stainless steel complying with ASTM A 240/A
240M. Drop legs and headers shall have a nominal wall thickness
of 2.7788 mm 0.1094 inch (12 gauge). Header dimensions shall be
as indicated with dimensional tolerances complying with ASTM A
530/A 530M and ASTM A 554. Welded wrought stainless steel
fittings and welded stainless steel tubular products shall be
fabricated in accordance with ASTM A 774/A 774M and ASTM A 778.
All welding shall be performed in the shop. Filler wire shall be
added to all welds to provide a cross section equal to the parent
material. Butt welds shall have full penetration to the interior
surface. Interior weld beads shall be smooth, evenly distributed,
with an interior projection not exceeding 2 mm 1/16 inch. Outside
weld areas shall be wire brushed with stainless steel brushes.
After fabrication, the assembly shall be passivated by pickling
and shall be completely neutralized. The quick-coupling flange
shall be nickel plated ductile iron with a stainless steel hinge
SECTION 11375A
Page 21
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