d.
Manual Activation. There shall be a manual activator located at
each operator's console and at least two locations inside the chamber.
e.
Booster Pumps.
Booster pumps, when used, shall have a separate
independent power supply.
Activation control circuits shall have emergency
standby provisions.
f.
Use Indicators. A visual and aural indication of the system's
activation shall be provided at each operator's control console. It shall
also be tied into the station's exterior fire alarm system.
g.
Manual System. A manual extinguishing system shall also be
provided within each chamber.
(1) System shall consist of two three-quarter-inch water
handlines, located adjacent to the opposite ends of the chamber,
(2)
At least one handline shall be located in each lock.
(3) Each handline shall be activated by a manual quick-opening
quarter-turn valve,
(4) Handline pressures shall be approximately 50 psi above the
chamber pressure.
h.
Electrical Circuits Shutdown. Activation of any fire
extinguishing system shall cause all electrical circuits, except
communication circuits, to be automatically deactivated. It shall also
automatically shut down the oxygen supply to the chamber.
i.
Gas Pressurization. A good method of providing the force to drive
the fire extinguishing water from the storage tanks is gas under pressure.
The gas driving the water is normally supplied to the tank by a pressure
regulator which senses chamber pressure and supplies gas to the tank at some
fixed pressure higher than the chamber pressure. The driving force is
usually set at about 50 psi. A typical gas pressurized fire extinguishing
system is shown in Figure 8-1.
When designing a system of this type, it is important to have the sensing
lines and the pressure regulator with its supply lines very generously sized.
This is necessary so that the driving force is maintained while the water is
being driven from the tank. An important consideration which has been
frequently overlooked is the fact that the regulator must vent off pressure
when the main chamber is returning to the surface.
j.
Automatic Operation. It is desirable to have an automatic fire
detection and extinguishing system in chambers to keep the critical response
time as short as possible, At the time of preparation of this manual, there
are no fire detectors available with sufficient proven reliability, that can
be depended upon to activate the system if there is a fire and which will not
respond to false alarms and drench the occupants and equipment,
intermittently during a dive.
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