boiler foundation and floor.
2.2.3.2
Welded Wall
a.
Inner Casing:
Provide No. 10 gage inner casing for tangent tube
construction.
b.
Insulation and Firebrick: Back up the walls and roof of the
furnace with not less than 63.50 mm 2 1/2 inches of block
insulation (816 degrees C1500 degrees F class) or ASTM C 155
insulating firebrick. Provide standard welded casing or lagging
to cover and protect insulation.
c.
Furnace Roof Tube Openings: Where necessary, such as where the
furnace roof tubes are separated to enter the drum, the opening
shall be completely inner cased and filled with ASTM C 401
castable refractory.
2.2.3.3
Tube and Tile Furnace Construction
Sides, front and rear walls, and the roof of the boiler, as far as is
practical, shall include water wall tubes backed up with not less than a
thickness of 63.50 mm 2 1/2 inches of super duty Class, regular type, ASTM
C 27 fire brick followed by high temperature block insulation 816 degrees C
1500 degrees F Class or ASTM C 155 insulating firebrick. Insulation shall
not be less than 127 mm 5 inches thick on the furnace walls and roof, 100 mm
4 inches thick on the side walls beyond the furnace, and 76 mm 3 inches
thick on the rear wall, consisting of two layers with staggered joints.
Plaster the entire exterior of the setting with a thin coating of plastic
high temperature cement before the casing is applied.
2.2.3.4
Drum, Header and Miscellaneous Insulation
a.
Drum Heads: Insulate drum heads with a minimum thickness of 51 mm
2 inches of calcium silicate blocks applied in two 25 mm one inch
layers with 25 mm one inch mesh wire fabric embedded between
layers. Entire surface shall be neatly finished with 13 mm 1/2
inch coat of smooth, hard finish hydraulic setting insulating
cement with one inch chicken wire mesh embedded therein. Neatly
finish drum heads with a field applied 0.47 kg 14 ounce per square
meter yard glass cloth.
b.
Drum Top and Header: Insulate the top half of the steam drum as
previously specified for drum heads, but finish with 16 gage
welded steel casing. Provide insulation to the flange on smoke
outlet of the boiler. Insulate headers and downcomer tubes with
not less than 38 mm 1 1/2 inch thick calcium silicate blocks
banded in place, covered with 13 mm 1/2 inch thick coat of
hydraulic setting insulating cement and enclosed in an 18 gage
metal lagging with openings for access to handhole fittings, as
required.
c.
Miscellaneous: Provide special firebrick and tile required in
connection with fitting of doors and seals, and around stoker and
headers. Build arches of wedge brick where arches are required
for door openings. Line doors exposed to furnace radiation for
full depth of door with plastic refractory properly fastened to
door.
Caulk expansion joints with temperature resisting caulking
material at points where setting joins parts of boiler. Provide
SECTION 15502N
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