provided. An adjustable stop to prevent the knee joint from
opening beyond 180 degrees shall be provided. The hanger pipes
and air headers shall be fabricated from 304L stainless steel in
accordance with ASTM A 240/A 240M. The upper hanger pipes shall
be Schedule 10S. Lower hanger pipes shall be Schedule 5S. Air
header pipes shall be 12 gauge. Header dimensions shall be as
indicated with dimensional tolerances in accordance 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,
and 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 hanger pipes
shall be welded to the upper swing joint and knee joint. The
header pipe shall be flange connected to the hanger pipe.
Diffuser connectors shall be welded to the header. The header
shall have welded end caps.
b.
Carbon Steel Systems: The upper swing joint and knee joint shall
be cast steel. Connection between the two sections shall be by
means of a stainless steel pin working in a graphite bronze
bushing. Bearings shall be graphite impregnated cast bronze in
accordance with ASTM B 584. Brass seal rings with labyrinth
grooves shall be provided between the two joint sections. A
grease fitting to lubricate the seal rings shall be provided. An
adjustable stop to prevent the knee joint from opening beyond 180
degrees shall be provided. The hanger and header pipes shall be
schedule [40] [80] carbon steel pipe in accordance with ASTM A 524.
Header dimensions shall be as indicated. Welding shall be
performed in the shop. After fabrication, the assembly shall be
painted with the manufacturer's standard finish. The hanger pipes
shall be welded to the upper swing joint and knee joint. The
header pipe shall be flange connected to the hanger pipe.
Diffuser connectors shall be welded to the header. The header
shall have welded end caps.
c.
Galvanized Steel Systems: The upper swing joint and knee joint
shall be cast iron. Connection between the two sections shall be
by means of a stud equipped with a spring to maintain seal between
the faces. Graphite impregnated bronze seal rings and bearings in
accordance with ASTM B 584 shall be provided. Grease fittings for
lubrication shall be provided. The hanger and header pipes shall
be schedule [40] [80] galvanized steel pipe in accordance with
ASTM A 53/A 53M. Header dimensions shall be as indicated. The
header shall consist of two lengths of pipe, flange connected to a
cast iron tee. The hanger pipes shall be screw connected to the
upper swing joint and knee joint, and flange connected to the
header tee. Diffuser connectors shall be welded to the header.
The header shall have gasketed, screwed end caps.
d.
Fiberglass Systems: The upper swing joint and knee joint shall be
of the trunnion sleeve type manufactured of glass reinforced
synthetic resin capable of continuously operating in pH levels of
5.0 to 9.0 and at gas temperatures up to 108 degrees C 225 degrees
SECTION 11375A
Page 23
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