weight, minimum, steel pipe conforming to ASTM A 106/A 106M Grade B.
Blowoff valves shall be the balanced seatless type unless otherwise
approved.
2.2.4.10
Steam Nonreturn Valve
Steam nonreturn valve of size and pressure rating shown shall be installed
in the steam supply line from each boiler. Valves shall be arranged to
close automatically when there is a pressure differential of 34.5 kPa 5 psi
between the boilers and steam headers and shall also be arranged to operate
as stop valves. Valves shall be set with the stem up, either inclined or
vertical, and shall be of the rising stem type. Valves shall be of the
angle or straight-way type and shall operate without chattering, hammering,
or sticking. Valves shall be cast steel.
2.2.4.11
Feedwater Regulator
Feedwater regulator, sized for the application, shall be connected
complete with all necessary piping and accessories for automatic operation.
Valved bypass shall be provided around control valve. [Units shall be
provided with device to lock regulator in existing position in case of
power failure.] [Units shall be provided with manual/automatic selector
panel located on instrument panel.] Feedwater control element shall be
provided with a drain valve. The feedwater line shall be fitted with a
thermometer well.
2.2.4.12
Soot Blowers
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NOTE: Manually operated rotary soot blowers are
normally supplied on boilers up to 6 Megawatts (20
million Btuh). The designer shall delete the
inappropriate type of soot blower.
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Soot blowers shall be furnished as required to effectively clean all tube
surfaces within the boiler. Steam blowing pressure shall be adjustable.
Elements within the boiler shall be constructed of heat-resisting alloys
suitable for the flue gas temperature encountered and shall be removable
without disturbing the boiler tubes. Soot blowers shall be furnished
complete with necessary auxiliaries and shall be connected in accordance
with the manufacturer's recommendations. Soot blowers shall be
[permanently-mounted, rotary type manually-operated by a single chain.
Valve shall be quick-opening, positive-closing type located in the blower
head, external to the boiler, with the working parts protected from the
furnace gases, and valve shall be operated by the same chain that rotates
the element. Chains shall be continuous extending to within easy reach of
the operating floors. Blowers shall be furnished complete with necessary
auxiliaries and shall be connected in accordance with the manufacturer's
recommendations.] [electrically-operated rotary or retractable type, except
that soot blowers exposed to flue gas temperatures over 815 degrees C 1,500
degrees F shall be retractable type only. Rotary type soot blowers shall
be provided with a quick-opening, positive closing type valve located in
the blower head, external to the boiler, with the working parts protected
from the furnace gases, and valve shall be operated by the same motor that
rotates the element. Electrically-operated retractable type soot blowers
shall have either single motor-driven, totally-enclosed drive carriage with
dual rack-and-pinion drives or dual-motor electric drive enclosed in a
protective steel housing. Electrically-operated soot blowers shall include
SECTION 15559A
Page 27
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