TYPES OF FIREMAIN SYSTEMS
Learning Objectives: Recall the location, design, and
operation of shipboard fire-fighting systems to include
Navy ships have three basic types of firemain
fi r e m a i n , a q u e o u s fi l m - f o r m i n g f o a m ( A F F F ) ,
systems. They are as follows:
magazine sprinkler, installed carbon dioxide (CO2),
1. The single-main system
To fight fires onboard ship effectively, damage
2. The horizontal loop system
control personnel must not only be very familiar with
3. The vertical offset loop system
the primary damage control equipment but must also
be knowledgeable of fire-fighting systems onboard
The type of firemain system in any particular ship
Navy ships. This chapter provides general information
depends upon the characteristics and functions of the
about fire-fighting systems. Detailed information is
ship. Small ships generally have a straight-line,
contained in the manufacturer's technical manual for
single-main system. Large ships usually have one of
the loop systems or a composite system, which is some
combination or variation of the three basic types.
The design of the three basic types of firemain
systems is as follows:
Learning Objective: Recall the function of a shipboard
firemain and the components of the three basic types of
1. The single-main firemain system shown in
firemain systems onboard Navy ships along with the
figure 6-1 consists of a single piping run that extends
design and use of magazine sprinkler systems.
fore and aft. This type of firemain is generally installed
near the centerline of the ship, extending forward and aft
The firemain system receives water pumped from
as far as necessary.
the sea. It distributes this water to fireplugs, sprinkling
systems, flushing systems, machinery cooling-water
2. The horizontal loop firemain system shown in
systems, washdown systems, and other systems as
figure 6-2 consists of two single fore-and-aft,
required. The firemain system is used primarily to
cross-connected piping runs. The two individual
supply the fireplug and the sprinkling systems; the
lengths of piping are installed in the same horizontal
other uses of the system are secondary.
plane (on the same deck) but are separated athwartships
as far as practical.
Figure 6-1. Single-main firemain system.