F. All areas of high stress shall be ribbed to provide increased
strength. Each rotating bearing surface shall be provided with
ring type air seals. The assemblies shall be held together by a
13 mm 1/2 inch diameter stainless steel rod with locking nuts.
The hanger and header pipes shall be reinforced thermosetting
resin pipe in accordance with ASTM D 2310, Type I, Grade l, Class
F, ASTM D 2992, and ASTM D 2996. The pipe shall be in accordance
with the following: 275.8 MPa 40,000 psi minimum hoop stress; 65.5
MPa 9,500 psi minimum tensile strength; 131.0 MPa 19,000 psi
minimum axial compression strength; minimum 55 Barcol hardness;
54.75 degree wind angle; 2.8 mm 0.110 inch minimum wall thickness.
Ultraviolet protection shall be provided for the pipe material.
The liner resin shall be 85 to 89 percent resin with glass filler
and shall be at least 0.51 mm 0.020 inch thick. Joints shall be
filled epoxy adhesive joints. Header dimensions shall be as
indicated. The hanger shall be flange connected to the header.
2.4.3.3
Supports and Guides
Supports and guides shall be provided as required for support and leveling
of the header.
2.4.4
Fixed Header Air Distribution System
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NOTE: Delete inapplicable header types and
materials of construction.
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A fixed header air distribution shall be provided as indicated and shall
consist of a dropleg assembly, fixed headers, and supports. The system
shall be compatible with the air main and the specified diffusers.
2.4.4.1
Drop Leg Assembly
A drop leg assembly shall be provided to connect the fixed headers to the
air main. The assembly shall be of the dimensions indicated.
2.4.4.2
Fixed Headers
The fixed headers shall be of the dimensions and configuration indicated.
Header connections shall be of a type allowing rotational adjustment of
individual header sections and shall be of sufficient strength to transmit
the longitudinal forces caused by expansion and contraction of the header.
The headers shall be designed to allow expansion and contraction over a
temperature range of 70 degrees C 125 degrees F without damage to the
system. Rotation of the header due to thermal expansion and contraction
shall be prevented. Fixed headers shall be stainless steel systems or
fiberglass systems as follows:
a.
Stainless Steel Systems: All welded parts of the system shall be
fabricated from 304L stainless steel in accordance with ASTM A
240/A 240M. [Stainless steel pipe shall have a 2D finish in
accordance with ASTM A 480/A 480M.] Pipe wall thickness shall be
as follows: 250 mm 10 inches diameter and less shall be 1.5875 mm
0.0625 inch (16 gauge) thick; 300 mm 12 inches diameter shall be
1.9837 mm 0.0781 inch (14 gauge) thick; 350 mm 14 inches through
450 mm 18 inches diameter shall be 2.7788 mm 0.l094 inch (12 gauge)
thick; 500 mm 20 inches diameter shall be 3.1750 mm 0.1250 inch
SECTION 11375A
Page 24
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