TM 5-1940-321-13&P
( 3 ) Valves. Excessive air pressure will be released by the four intercommunicating
valves or five CO2 overpressure valves. The I/C overpressure release valves only
operate at very high air pressure. The intercommunicating valves open between
700/800 mb (10.2/11.6 psi), and the CO2 overpressure valves open at 340 mb (4.9
psi). After opening and releasing excess pressure, either will close automatically.
The CO2 valves will close at around 275 mb (4.0 psi), Their purpose is to protect the
craft from damage due to high air pressure. The pressure at which they release
pressure is much higher than the correct inflation pressure of 240 to 280 mb (3.5 to
4.1 psi) for the buoyancy tubes. The inflatable keel does not have any overpressure
release valves. The F530 IAB contains five CO2 overpressure valves, four
intercommunicating valves, two CO2 inlet valves, and two isolator clamps. These
items are used as follows:
(a) CO2 Overpressure Valves. The overpressure valves function automatically. They
open to release excess pressure at 338 mb ( 4.9 psi) and close and reset at
approximately 275 mb (4.0 psi), =/- 10%.
(b) Intercommunicating Valves. In addition to their overpressure release function, the
intercommunicating valves have several other functions. These valves, depending
on their position setting, allow air to flow between adjacent air chambers or isolate
the air in each chamber. The intercommunicating valves accept an air hose for
inflation and a pressure gauge for pressure checks.
(c) CO2 Inlet Valves. The two CO2 inlet valves are used only with the automatic CO2
inflation system. Operation of the automatic CO2 inflation system is described in
valves should be kept clean by installing a nylon plug in each valve. The nylon
plugs are slotted for a screwdriver A small O-ring is installed behind the nylon plug
to keep the system failsafe and airtight.
(d) Isolator Clamps. The isolator clamps are used to seal off the air connection
between the upper and lower buoyancy tubes after inflation. They are removed for
inflation, deflation, and pressure checks. They remain installed at all other times.
4-5
