|
Firetube boilers are used in applications that
require moderate pressures and moderate demand. Firetube boilers generally have
2-inch diameter or larger tubes. They are usually straight and relatively short
so that the hot gases of combustion experience a relatively low pressure drop
while passing through them.
Firetube boilers are generally built similar to a
shell and tube heat exchanger. The water space surrounding the tubes is usually
contained by a large cylindrical or flat surfaced vessel. For this reason,
firetube boilers are rarely designed for more than 300 psi as the required wall
thickness would be too excessive.
Firetube boilers have a fairly large amount of
contained water so that there is a considerable amount of stored heat energy in
the boiler. This also allows for load swings where large amounts of steam or hot
water are required in a relatively short period of time, as often happens in
process applications.
Firetube boilers can take a great deal of abuse and inattention and still
function at competent levels. Firetube boilers have a life expectancy of 25
years or more. You can find boilers 75 years old and older are still known to be
in operation.
Consistent maintenance and careful water
treatment (as we will discuss in the next segment on the third boiler element —
water) go a long way towards insuring the long life of these boilers.
Packaged Firetube Boilers
There was a time when an end-user would purchase a boiler shell from one place
and firing equipment from another and go down to the hardware store to get the
controls and wiring in hopes of making it work...however, in the past 70 years
standardized packaged boiler units have taken the place of those “one-of-a-kind”
units. Packaged boilers are simply boiler/burner packages complete with all trim
components that make them ready from the factory to be shipped and installed as
a complete unit.
Packaged boilers are self-contained units that
save their owners in installation cost at the time of delivery. Their only
requirements after delivery are for electrical, water, fuel and chimney hook-up.
These units are also fire tested at the factory before shipment. Those fire test
reports are supplied to the owners and can be helpful with start-up settings and
efficiency data.
There are two major types of packaged firetube
boilers:
Scotch | Firebox
Two other types of firetube boilers are:
Cast Iron | Vertical
Firetube
|
