2.2.2.3
HTW Generator Roof
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NOTE: For personnel safety, the design temperature
of the casing surface should not exceed 65 degrees C
(150 degrees F). Should the designer wish to use a
design surface temperature between 55 and 65 degrees
C (130 and 150 degrees F), an economic evaluation
must be performed. The evaluation must determine if
the additional capital costs for insulation outweigh
the cost savings due to reduced boiler radiation
losses.
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Refractory lining conforming to manufacturer's requirements shall consist
of not less than 65 mm 2-1/2 inches of high-duty refractory backup behind
the roof tubes and sufficient thickness of high temperature block
insulation or mineral-wool blanket suitable for the temperature encountered
to limit casing temperature in the furnace area to [55] [_____] degrees C
[130] [_____] degrees F, with a surface air velocity of 508 mm/second 100
fpm and an ambient air temperature of 25 degrees C 80 degrees F when
operating at full capacity. Manholes and other inspection and access
openings, and identification plates and stamps shall have insulation
finished neatly against a metal ring provided for this purpose.
2.2.2.4
Bridge Walls
Bridge walls exposed on all sides to radiant heat and the products of
combustion shall be constructed of super-duty refractory not less than 457
mm 18 inches thick, conforming to manufacturer's requirements. Walls having
only the front side exposed to radiant heat and the products of combustion
shall have front facing and cap constructed of 225 mm 9 inches of
super-duty refractory and back facing of not less than 225 mm 9 inches of
low-duty firebrick. The base of the wall shall be common brick.
2.2.2.5
Settling Chamber
Settling chamber for the removal of fly ash shall be provided below the
last pass of each HTW generator. Chamber shall have means for frequent
cleaning without shutting down the HTW generators.
2.2.2.6
Expansion Joints
Expansion joints shall be provided where indicated and elsewhere as
required to permit all 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 mineral wool suitable for 925 to 1095 degrees C 1700 to 2000
degrees F. In addition, to allow for expansion of the inner face, a series
of 3 mm 1/8 inch wide vertical openings, spaced 1.8 m 6 feet apart, shall
be provided on the furnace side of the wall. Proper provision shall be
made for expansion and contraction between boiler foundation and floor as
specified.
2.2.2.7
Firebrick
Firebrick shall be laid up in air-setting mortar. Each brick shall be
dipped in mortar, rubbed, shoved into its final place, and then tapped with
SECTION 15555A
Page 24
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