chemical feed. Continuous blowdown and chemical feed pipe inside
of drum shall be stainless steel.
2.2.2.2
Headers
Horizontal lower and upper side wall headers shall preferably be square.
However, round headers are acceptable, provided approved stoker seals are
provided. Provide rear wall and front wall headers. Protect the front
wall header by studs and pack with insulating cement. Provide headers with
key caps or gasketed type handhole fittings.
2.2.2.3
Tubes
Boiler design pressure shall not be less than 1724 kPa (gage) 250 psig.
Water tube rows and first two rows of main boiler bank shall be one gage
heavier than other tubes. Tubes shall be resistance welded or seamless,
ASME BPVC SEC II-A SA-178/SA-178M, Grade A carbon steel not less than 63.50
mm 2 1/2 inches O.D.; tubes shall not be reduced in size at the boiler
drums. Manufacturer shall indicate the size, weight, and kind of tubes on
the submittal drawings. Furnace walls and roof shall be water cooled.
Radii of bends in tubes shall be such that standard turbine type cleaners
can easily pass through the full length of the tubes.
a.
When a boiler is provided with welded wall construction, the tube
side walls, front wall, and furnace roof shall be of gastight
construction, tubes shall be skin cased for gastight construction.
b.
The width of the water wall tubes, as determined by the outside
diameter of the tubes, shall cover at least 50 percent of each of
the front, rear furnace, side walls, and roof of the boiler.
c.
Tube connections to upper drum shall be so arranged that the ends
of downcomer tubes shall be covered with water when the water
level in the steam drum is 50 mm 2 inches below the bottom of the
gage glass with the gage glass being centered at the normal water
level in the drum. Tube bends shall be free of wrinkles and at no
point of the bend shall the diameter of the tube be more than 3 mm
1/8 inch less than the minimum allowable diameter of the tubes.
d.
Space boiler and water wall tubes so that tubes may be removed and
replaced without disturbing another tube.
2.2.3
Boiler Setting and Insulation
Provide a complete setting including firebrick, refractory tile,
insulation, tile supports, supporting steel, steel casing, material for
expansion joints, and necessary work and materials to provide a complete
gas envelope for the convector and water walls.
2.2.3.1
Expansion Joints
Provide expansion joints where required to permit brickwork to expand
freely without interference with the boiler. Joints shall be of adequate
width, tightly sealed against leakage, and free from mortar, with the outer
100 mm 4 inches sealed with resilient material suitable for 927 to 1093
degrees C 1,700 to 2,000 degrees F. In addition, to allow for expansion of
the inner face, a series of 3 mm 1/8 inch wide vertical openings spaced
1.83 meters 6 feet apart shall be provided on the furnace side of the wall.
Proper provision shall be made for expansion and contraction between
SECTION 15502N
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