| How Does A Boiler Work?
A boiler is water containing vessel which
transfers heat from a fuel source (oil, gas, coal) into steam which is piped
to a point where it can be used to run production equipment, to sterilize,
provide heat, to steam-clean, etc.
The energy given up by the steam is sufficient
to convert it back into the form of water. When 100% of the steam produced
is returned to be reused, the system is called a closed system.
Examples of closed systems are closed steam heating, hot water heating,
and "one-pipe" systems.
Since some processes can contaminate the steam,
so it is not always desirable to feed the condensate back into the boiler.
A system that does not return the condensate is called an open system.
The two main types of boilers are:
- Firetube - the fire or hot gases are directed through the inside
of tubes within the boiler shell, which are surrounded by water. The tubes
are arranged in banks so that the gases can be passed through the boiler
up to 4 times before passing out the stack. This system exposes the maximum
heat transfer surface to the water. Firetube boilers are also known as
shell boilers and can produce up to approximately 750 hp or 25,000 lbs
of steam per hour. 80% of boilers in use are of this configuration.
- A subtype of this boiler is the packaged
boiler, shipped complete with fuel burning equipment, mechanical
draft equipment, automatic controls and accessories and is designed to
function automatically with a very minimum of attention. It is particularly
important to prevent scale formation in this type of boiler.
- Watertube - the fire or hot gases are directed to and around the outside
of tubes containing water, arranged in a vertical position. Watertube boilers
are usually rectangular in shape and have two or more drums. The separation
of steam and water takes place in the top drum, while the bottom drum serves
as a collection point for sludge. This system is usually used when more
than 750 hp or several hundred thousand lbs of steam per hour, are needed.
- There are other designs with special configurations,
adapting them to particular applications.