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 the fuels specified. When necessary (if there is sulfer in the
specified fuel, and the designed inlet temperature could fall below the
acid dew point), provide a feedwater temperature control system to maintain
temperatures above the acid dew point. Provide casing of not less than 12
gage steel plate reinforced as required with support lugs and breeching
flanges. Provide building framing steel to support the economizer.
[Provide built-in soot blower for each economizer to thoroughly clean the
surfaces exposed to the flue gas.] Design the economizer 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.
d.
Temperature indicator on feedwater inlet.
e.
Temperature indicator on flue gas outlet.
f.
Temperature indicator on flue gas inlet.
g.
Temperature alarm switches for high and low flue gas temperatures.
h.
Alarm with trouble light and silencing switch.
i.
Panel with annunciator and temperature indicators for feedwater
inlet, feedwater outlet, flue gas inlet and flue gas outlet for
each economizer.
j.
A drain valve downstream of the economizer before the shutoff
valve.
k.
A stack flue gas temperature control system to control and limit
flue gas temperature to not less than 149 degrees C 300 degrees F
by modulating motorized feedwater control valves in a bypass
around the economizer. Provide shutoff valve on each side of the
control valves with a strainer upstream of each valve. Provide
this system in parallel to the manual shutoff and bypass described
above.
l.
Differential pressure indicator on water side.
m.
Differential pressure indicator on gas side.
n.
Pressure gages on feedwater inlet and outlet.
SECTION 15511N
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