1A1. Importance of the air systems to submarines.
The importance of the air systems
to a submarine cannot be overemphasized
since virtually every operation in the diving
and surfacing procedure is dependent upon
air provided by one or more of the air systems.
Some of the more important operations
depending on air pressure are the following:
a. The main hydraulic system operates
because of the air pressure maintained in the
b. Torpedoes are discharged from the
submarine by air.
c. Tanks are blown by air.
d. The main propulsion engines are
started by air.
Air, or more specifically compressed air, is
necessary in order to surface, submerge, attack,
and cruise. These functions, of course,
are in addition to the use of compressed air
and oxygen to revitalize the air in the ship
after long periods of submergence. Pressure
in the boat, a test for tightness, utilizes air.
The air systems represent, therefore, one
of the most versatile of all systems aboard a
submarine, in that they are capable of performing
either as primary or secondary
functions many of the operations performed in a
1A2. Basic principles of compressed air. The
basis of the air systems is compressed air,
which as the name implies, is air under pressure
confined within the limits of a container.
The force required for compression of the air
is provided by the high-pressure air compressor,
a simple machine which compresses air by
means of a series of pistons, designed so that
one or more pistons discharges air into
another for further compression and finally
through lines to banks for storage. Air can
be compressed easily aboard a submarine, as
it requires a relatively small plant and
comparatively simple equipment. It can be stored
at any convenient place and is always ready
for use. Its action can be regulated to produce
a low or high pressure, and yet it has
enough elasticity or compressibility to cushion
its impact against the equipment it operates.
It consumes no valuable materials and
can be supplied to any part of the submarine
by simply extending a line from the air
supply. Air, once stored, requires no further
expenditure of energy for operation; but
rather is a source of power for the operation
of other equipment.
B. TYPES AND RELATIONSHIPS OF AIR SYSTEMS
1B1. General information. There are five
separate air systems on the submarine: the
3000-pound high-pressure and torpedo impulse
system, the 600-pound main ballast tank
(MBT) blowing system, the 225-pound service
air system (ship's service air), the 10-pound
main ballast tank (MBT) blowing system and the
salvage air system. (See Figure
The 600-pound MBT blowing system and
the 225-pound service air system receive their
supply of air from the 3000-pound air system.
The 10-pound MBT blowing system is
an independent system with its own
low-pressure blower. The internal compartment
salvage air system is dependent upon the 225-pound
service air system, while the external
compartment salvage air system is entirely
dependent upon an outside source for its
supply of air.
1B2. The 3000-pound and torpedo tube impulse
air system. The 3000-pound air system
consists of the 3000-pound high-pressure compressors,
the high-pressure manifold, the interconnecting
piping, valves, and compressed
air banks. The main function of the 3000-pound
air system is to compress, store, and
supply air at the maximum pressure of 3000
pounds per square inch for use within the
3000-pound, the 600-pound, and the 225-pound
The 3000-pound air system also supplies
air to the hydraulic accumulator air-loading
manifold and to the forward and after 600
pound Grove reducing valves which supply
the forward and after torpedo tube impulse-charging
The 3000-pound air system is equipped
with an external charging connection so that
the system may be supplied with air from an
1B3. The 600-pound MBT blowing system.
The function of the 600-pound MBT blowing
manifold and system is to remove water ballast
from the main ballast tanks, or the fuel
ballast tanks when they are used as main
ballast tanks, during surfacing of the submarine.
It receives its supply of compressed
air from the high-pressure system through the
1B4. The 225-pound service air system. The
225-pound service air system or, as it is
sometimes called, ship's service air, in
addition to blowing the variable group of tanks,
provides the compressed air for all the
miscellaneous services aboard the submarine. The
225-pound system consists of the 225-pound
service air manifold, interconnecting piping,
and various valves.
1B5. The 10-pound MBT blowing system.
When the submarine has surfaced, the 10-pound
main ballast tank blowing system is
used to conserve the compressed air stored in
the ship's air banks. The system consists of its
own low-pressure blower, control manifold,
and piping to the various main ballast tanks.
The 10-pound system is operated only after
the submarine has surfaced sufficiently to
permit the opening of induction valves and
1B6. The salvage air system. This system
actually consists of three separate systems
the MBT external salvage, compartment external
salvage, and compartment internal salvage.
The external salvage connections permit
compressed air from an outside source to be
supplied to the tanks and/or compartments,
while the internal salvage system utilizes the
ship's air for compartment salvage only.
Figure 1-1. COMPREHENSIVE SCHEMATIC OF AIR SYSTEMS.
Copyright © 2004 Historic Naval Ships Association
All Rights Reserved
Version 1.10, 22 Oct 04