7-6
U.S. Navy Diving Manual—Volume 2
7-2.2.2.2
Inspection Requirements. Open-circuit scuba cylinders must be visually
inspected at least once every 12 months and every time water or particulate matter
is suspected in the cylinder. Cylinders containing visible accumulations of corro-
sion must be cleaned before being placed into service. Commercially available
steel and aluminum scuba cylinders, as specified in the NAVSEA/00C ANU list,
which meet DOT specifications, as well as scuba cylinders designed to Navy spec-
ifications, must be visually inspected at least annually and must be hydrostatically
tested at least every five years in accordance with DOT regulations and
Compressed Gas Association (CGA) pamphlets C-1 and C-6.
7-2.2.2.3
Guidelines for Handling Cylinders. General safety regulations governing the
handling and use of compressed gas cylinders aboard Navy ships are contained in
NAVSEA 0901-LP-230-0002, NSTM Chapter 550, “Compressed Gas Handling.”
Persons responsible for handling, storing, and charging scuba cylinders must be
familiar with these regulations. Safety rules applying to scuba cylinders are
contained in paragraph 7-4.5. Because scuba cylinders are subject to continuous
handling and because of the hazards posed by a damaged unit, close adherence to
the rules is mandatory.
7-2.2.3
Cylinder Valves and Manifold Assemblies. Cylinder valves and manifolds make
up the system that passes the high-pressure air from the cylinders to the first-stage
regulator. The cylinder valve serves as an on/off valve and is sealed to the tank by
a straight-threaded male connection containing a neoprene O-ring on the valve’s
body.
7-2.2.3.1
Blowout Plugs and Safety Discs. The cylinder valve contains a high-pressure
blowout plug or safety disc plug in the event of excessive pressure buildup. When
a dual manifold is used, two blowout plugs or safety disc plugs are installed as
specified by the manufacturers’ technical manual.
For standard diving equipment, a safety disc plug similar to new issue equipment
is recommended. The safety disc plug and safety disc are not always identified by
a National Stock Number (NSN), but are available commercially.
7-2.2.3.2
Manifold Connectors. If two or more cylinders are to be used together, a manifold
unit is needed to provide the necessary interconnection. Most manifolds incorpo-
rate an O-ring as a seal, but some earlier models may have a tapered (pipe) thread
design. One type will not connect with the other type.
7-2.2.3.3
Pressure Gauge Requirements. A cylinder valve with an air reserve (J valve) is
preferred. When a cylinder valve without an air reserve (K valve) is used, the
scuba regulator must be equipped with a submersible pressure gauge to indicate
pressure contents of the cylinder. The dive must be terminated when the cylinder
pressure reaches 500 psi for a single cylinder or 250 psi for twin manifold cylin-
ders. The air reserve mechanism alerts the diver that the available air supply is
almost exhausted and provides the diver with sufficient reserve air to reach the
surface. The air reserve mechanism contains a spring-loaded check valve. When it
becomes increasingly difficult to obtain a full breath, the diver must reach over the
