arrangement. Insulation shall be suitable for sustained flue gas
temperature of 480 degrees C 900 degrees F with intermittent temperatures
up to 650 degrees C 1200 degrees F and the wall section shall provide a "U"
factor of approximately 0.26. Stacks shall be fabricated of steel
conforming to ASTM A 242/A 242M for both inner and outer shell. Inner
shells of each section shall be provided with an air-sealed and concealed
expansion and contraction device to allow for differential expansion of
inner and outer shells. Stacks shall be extended above the roof to the
height indicated. Plastic materials polyetherimide (PEI) and
polyethersulfone (PES) are forbidden to be used for vent piping for
combustion gases.
2.14
BLOWOFF TANK
Blowoff tank [shall be constructed of 28 MPa 4000 psi reinforced concrete
as specified in Section 03300A CAST-IN-PLACE STRUCTURAL CONCRETE, and shall
be fitted with a bolted steel manhole cover and frame. Blowoff pipe, vent
pipe, and drain pipe to sewer shall be installed in pipe sleeves built into
the concrete. The space between the pipe and sleeves shall be filled and
caulked with lead wool or similar material to make a water-tight
connection. The tank shall be divided into two sections by a baffle to
form a sediment chamber] [shall be constructed of steel in accordance with
NBBPVI NB-27.]
2.15
PUMPS
2.15.1
Boiler Feed Pumps
Boiler feed pumps shall be sized and designed for the specific application.
Pumps having a combined rating of flow and head that results in a wattage
horsepower rating less than 185 kW 250 bhp shall be furnished to meet the
design requirements of API Std 610. The pump shall be end-suction, top
discharge and be supported at its centerline. Pump sizes with higher
ratings than the above shall be horizontal-split case, multistage
centrifugal pumps. Casing construction shall be either volute or diffuser
design and shall also be supported at its casing centerline. All pump
ratings shall have, nominally, an excess in capacity of 10 percent above
the maximum continuous rating of the service. The required net positive
suction head (NPSH) at the pump design flow, head, and speed shall not
exceed 80 percent of the available system NPSH at the same flow, assuming a
low level in the storage tank. The pump's suction specific speed shall not
exceed 9000 at the pump's best efficiency point (BEP). The guaranteed NPSH
requirements shall reflect 3 percent breakdown criteria. The pump's
head-capacity (H-Q) curve shall be constantly rising to shutoff with no
point of inflection. There shall be no restriction to operation at any
point from minimum continuous flow to design flow.
2.15.1.1
Casings
Pumps shall have integrally cast suction and discharge flanges that shall
be drilled to meet the design pressure of the application. The maximum
operating temperature, for design purposes, of any feedpump shall not be
less than 204 degrees C 400 degrees F. Casings shall be drilled, tapped,
and provided with vent and drain connections. Pumps designed for this
service shall not require cooling at ratings below 375 kW 500 bhp. This
applies to both frame cooling or seal cooling. Below 375 kW 500 bhp, pumps
shall employ antifriction radial and thrust bearings lubricated by flinger
rings in a sealed housing. Seals shall be mechanical and air-cooled flush
piping conforming to API Std 610, Plan 23. Above 375 kW 500 bhp, pumps
SECTION 15559A
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