the plans and diagrams you will study, and to draw your
600 psi and temperatures up to 850°F. Others go as high
own rough sketches of the systems.
as 1200 psi and 975°F.
Remember that this chapter only gives general
Auxiliary Steam Systems
information on the various systems. Each ship is
different, even sister ships. Therefore, to actually know
your own ship's installation, you must check the details
low pressure, depending upon the units that they serve.
The high-pressure auxiliary steam system serves fire
and bilge pumps, various service pumps, and fuel oil
heaters. The piping and tubing is of the same material
as that used in the main steam system.
Steam forms when water has been sufficiently
The low-pressure auxiliary steam system is used for
heated. As heat is applied to a container partially filled
steam heat and for air ejectors in the distilling plant and
with water, the temperature of the water rises until the
main plant. Seamless steel, copper pipe, or copper
boiling point is reached. At this temperature, small
tubing is used, and the fittings and flanges are either
particles of water change to steam bubbles, which rise
welded or silver-brazed. The auxiliary steam system is
through the liquid to the surface and escape from the
routed in the form of a loop, with cross connections at
liquid. Although heat is continually being applied, the
suitable intervals. Branch lines serve the various units
temperature of both the water and the steam remains
of auxiliary machinery.
constant at the boiling point until all water in the
container has been converted to steam. About five
Auxiliary Exhaust System
times as much heat is needed to completely convert a
given quantity of water to steam at the boiling point
The auxiliary exhaust system receives exhaust from
without an increase in temperature, as is needed to raise
all noncondensing steam-driven auxiliaries and uses
the temperature of the same quantity of water from 32°F
to 212°F. The heat required to convert water at the
the distilling units, and the turbine gland sealing system.
boiling point to saturated steam at the same temperature
The pressure in the auxiliary exhaust system is
is called latent heat.
maintained at 15 psig. If the pressure goes above 15
There are two kinds of steam: saturated and
psig, automatic unloading valves (dumping valves)
superheated. Saturated steam is a vapor; superheated
allow the excess steam to go to either the main
steam is generally considered a gas. As long as steam
condenser or to the auxiliary condenser. If these
is in contact with water, it contains moisture in
unloading valves fail, relief valves allow the steam to
suspension. Steam in this condition and at the boiling
escape to the atmosphere. If the pressure in the system
point corresponding to its pressure is called saturated
drops too low, makeup steam is supplied from the
steam. Steam at the boiling point, but containing no
auxiliary steam system through an augmenting valve.
suspended moisture, is called dry saturated steam.
Saturated steam that has been heated to a temperature
Service Steam Systems
above the boiling point is called superheated steam.
Service steam systems are low-pressure systems
Main Steam System
that serve compartment heating units, galley
equipment, freshwater heaters, and laundry equipment.
The main steam system is a comparatively short
These are either constant service or intermittent service
system but a very important one. Steam is generated in
systems. Constant service steam systems are those in
the boiler, then routed to the propulsion turbines, to the
use the year around. Intermittent service steam systems
turbogenerators, and to the soot blowers via lines that
are for heating services not required except in cold
are made of alloy steel piping. On older ships, flanged
weather. Constant and intermittent service lines are
joints were used in the main steam system. On newer
usually cross-connected. Reducing valves in the
ships, welded joints are used whenever possible. The
branch lines leading from the 150-psi auxiliary steam
flanged takedown joints would be used only where the
system make it possible to reduce the steam to a suitable
line goes to major units such as the turbines. The
working pressure. Most service steam systems operate
pressures and temperatures maintained in the main
at 50 psi. The constant service system for laundry and
steam system are high. Some ships use pressures up to
tailor shop equipment operates at 100 psi.