2.3
ECONOMIZER
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NOTE: Economizers shall be specified for all
boilers with operating pressures greater than 345
kPa (gage) 50 psig and a capacity of 2 1/4 kg/sec
18,000 pounds per hournd larger. For boilers from
1/2 to 2 1/4 kg/sec 4,000 to 18,000 pounds per hour
the designer shall make the decision based upon a
specific economic analysis. This paragraph shall be
included as applicable.
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NOTE: Unless a coal or a fuel oil to be burned has
an uncommon tendency to foul tubes, finned tube
economizers should be suitable for both fuels.
Feedwater temperatures should be 110 degrees C 230
degrees F when sulphur (S) content of oil is 0.5
percent; 116 degrees C 240 degrees F, S=1.5 percent
- 2 percent; 121 degrees C 250 degrees F, S=2.0
percent - 2.7 percent. Where fuels having more than
1.5 percent sulfur content are to be fired, finned
tubes shall not be used unless they are steel tubes
covered with cast iron finned casing.
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Provide a modular [bare tube] [cast iron finned, steel tube] unit
constructed in accordance with the ASME BPVC SEC I. Water flow shall be
parallel to flue gas flow (incoming water shall enter at the same end that
the flue gasses enter the economizer).
2.3.1
Construction
Provide manufacturer's standard economizer design for the operating
conditions and the fuel(s) specified. Coordinate the amount of heating
surface with the flue gas conditions exiting the boiler or boilers on which
the economizer is to be applied to preclude reaching the "acid dew point"
for specified fuels. When necessary ( sulfer is present in the specified
fuel and the designed inlet temperature could fall below the "acid dew
point"), provide a feedwater temperature control system. Provide casing of
not less than 12 gage steel plate reinforced with steel support lugs and
breeching flanges. Provide building framing steel to properly support the
economizer. [Provide built-in rotary chain operated soot blowers for each
economizer to thoroughly clean surfaces exposed to flue gas.] Economizer
shall be designed so that internal construction can be easily cleaned and
inspected.
2.3.2
Equipment
Provide the following equipment for each unit:
a.
b.
Shutoff gate valve on feedwater outlet and shutoff globe valve on
inlet with globe valve bypass. Size valves as shown in economizer
piping detail
c.
Temperature indicator on feedwater outlet
SECTION 15501N
Page 47
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