Learning Objectives: Describe the principles and theory of steam generation.
Identify different types of boilers and the design requirements for boilers. Describe
the purpose and operation of the different types of boilers and their fittings and
accessories. Describe the methods and procedures for the testing and treatment of
boiler water. Describe methods and procedures involved in fireside and waterside
A boiler is an enclosed vessel in which water is
heated and circulated, either as hot water or steam, to
produce a source for either heat or power. A central
heating plant may have one or more boilers that use
gas, oil, or coal as fuel. The steam generated is used to
heat buildings, provide hot water, and provide steam
for cleaning, sterilizing, cooking, and laundering
operations. Small package boilers also provide steam
and hot water for small buildings.
A careful study of this chapter can help you
acquire useful knowledge of steam generation, types
of boilers pertinent to Seabee operations, various
fittings commonly found on boilers, and so on. The
primary objective of this chapter is to lay the
foundation for you to develop skill in the operation,
maintenance, and repair of boilers.
STEAM GENERATION THEORY
Describe the principles and
theory of steam generation.
To acquaint you with some of the fundamentals
underlying the process of steam operation, suppose
that you set an open pan of water on the stove and turn
on the heat. You find that the heat causes the
temperature of the water to increase and, at the same
time, to expand in volume. When the temperature
reaches the BOILING POINT (212°F or 100°C at sea
level). a physical change occurs in the water; the water
starts vaporizing. When you hold the temperature at the
boiling point long enough, the water continues to
vaporize until the pan is dry. A point to remember is that
THE TEMPERATURE OF WATER DOES NOT
INCREASE BEYOND THE BOILING POINT. Even if
you add more heat after the water starts to boil, the water
cannot get any hotter as long as it remains at the same
Now suppose you place a tightly fitting lid on the pan
of boiling water. The lid prevents the steam from
escaping from the pan and this results in a buildup of
pressure inside the container. However, when you make
an opening in the lid, the steam escapes at the same rate it
is generated. As long as water remains in the pan and as
long as the pressure remains constant, the temperature of
the water and steam remains constant and equal.
The steam boiler operates on the same basic principle
as a closed container of boiling water. By way of
comparison, it is as true with the boiler as with the closed
container that steam formed during boiling tends to push
against the water and sides of the vessel. Because of this
downward pressure on the surface of the water, a
temperature in excess of 212°F is required for boiling.
The higher temperature is obtained simply by increasing
the supply of heat; therefore, the rules you should
remember are as follows:
1. All of the water in a vessel, when held at the
boiling point long enough, will change into steam. AS
LONG AS THE PRESSURE IS HELD CONSTANT,
THE TEMPERATURE OF THE STEAM AND
BOILING WATER REMAINS THE SAME.
2. AN INCREASE IN PRESSURE RESULTS IN
AN INCREASE IN THE BOILING POINT
TEMPERATURE OF WATER.
A handy formula with a couple of fixed factors will
prove this theory.
The square root of steam pressure
multiplied by 14 plus 198 will give you the steam
temperature. When you have 1 psig of steam pressure,
the square root is one times 14 plus 198 which equals
212°F which is the temperature that the water will boil at