Boilers Industry Information
Boilers
are essentially tanks or vessels whose primary function is to
efficiently transfer heat from combustion gases to water or steam
through pipes, radiators, baseboards or convectors. Boilers are
produced by boiler manufacturers and are much larger in size and
capacity in comparison to residential units. The shapes of the vessels
can be cylindrical or boxed with small tubes housing the liquid to be
heated and/or converted into steam. The boilers produced by boiler
manufacturers are run by a fuel, such as natural gas, wood, coal,
pulverized coal, wood or wood waste. Some boilers use more than one
type of fuel. Electrical units heat fluid with less chance of
combustion, due to the lack of flammable fuel. Boilers are typically
constructed from cast iron and steel, but copper and stainless
steel are also sometimes used. Most boilers are housed
in a fireproof, well-ventilated, stable-air environment within the building
which they are heating.
Boiler manufacturers create fire-tube and water-tube boilers
as two basic designs. Fire-tube boilers work by forcing heat through
tubes immersed in water. They are typically used in low-pressure applications.
Water is circulated through tubes within the water-tube boiler enclosure.
Hot flue gases are passed over the tubes, heating the water, and then
discharged through a stack. Water-tube boilers are typically used in
higher pressure applications, due to their greater structural integrity.
Both designs are comparable in efficiency, but are not interchangeable
because of structural considerations.
The efficiency of boilers can be increased by combustion
controls that automatically operate burners to match the steam or hot
water demands on the boilers. Economizers are optional energy-saving
devices that can be fitted to existing boilers. They are
basically heat exchangers installed in the exhaust stack to preheat
the boiler feedwater, transferring a portion of the heat in the stack
gases to the water. Air preheaters also save energy by increasing the
temperature of the mixture of fuel and air prior to combustion, allowing
more availability of the heat resulting from combustion to heat water.
Turbulators are twisted pieces of metal inserted into the tubes of fire-tube
boilers that provide better heat transfer to the water by causing hot
gases to travel more slowly and with more turbulence. Oxygen trim controls
provide optimum efficiency by measuring the concentration of stack gas
oxygen and automatically adjusting the inlet air at the burner.
Boilers are often used as part of or with an industrial
furnace. They are utilized to heat commercial buildings or pools. Boilers are also used for purposes other than general heating.
They can provide the hot water needed for water-based manufacturing
processes such as papermaking. Boilers can be used for direct
injection processes as well. Mobile units are used in emergency relief
and military situations that require hot water for showers or steam
power for temporary energy.