Storage Tanks. Heated, above-ground, fuel oil tanks should be
insulated with a minimum of 1-1/2 inches of insulation and protected with an
exterior metal jacket.
Deaerators, condensate receivers, heat exchangers, and like
equipment shall be insulated for safety and optimum conservation of energy.
Breeching and Ducts. Flue gas breeching, regenerative type air
preheaters, economizers, and other exposed equipment between the boiler flue
gas exit and the stack shall be insulated.
Steel stacks shall be insulated in the annular space between shells
or on the outside. The insulation shall maintain the flue gas and inside
steel stack temperature above dewpoint. The exterior of the stack shall be at
a safe temperature.
Forced draft, overfire, underfire, and hot combustion air supply
duct shall be insulated.
For pipe sizes and engineering, refer to MIL-HDBK-1003/8.
Boiler Air Infiltration. Minimize boiler air infiltration. Ensure
a good fit and tight seal at mechanical joints, hopper doors, furnace and
pollution control system access and observation ports, etc. Air infiltration
directly affects boiler efficiency. Air leakage into the furnace causes
incomplete combustion, gives false excess oxygen values, and cools exit flue
gas temperatures. The results of air infiltration into the furnace are:
Incomplete combustion which wastes fuel and money.
b) False excess oxygen readings. Boiler will be put into
hazardous operating condition if operator adjusts for this incorrect reading.
c) Increased air flow increasing draft loss and fan power
requirements, and decreasing fan and stack capacity.
Lowered flue gas exit temperatures.
Affected performance of the economizer and air preheater.
False boiler operating efficiencies.
Affected flue gas dew point.
Soot Blowing. Efficiency, capacity, and draft loss of a boiler
installation depend on the condition of the heat transfer surface. For this
reason, soot blowers are provided in boilers, economizers, and air preheaters.
There are two types of soot blowers, air and steam. Soot blowers remove
accumulated deposits of soot, fly ash and slag from heat transfer surfaces.
They are also used to prevent fly ash from plugging equipment and air
passages. Materials and construction of soot blowers shall be in accordance
with the operating temperature of the furnace or equipment in which they are