8-16 Change A
U.S. Navy Diving Manual—Volume 2
Circling Line. The circling line is attached to the bottom end of the descent
line. It is used by the diver as a guide in searching and for relocating the
descent line.
Stage. Constructed to carry one or more divers, the stage is used to put divers
into the water and to bring them to the surface, especially when decompres-
sion stops must be made. The stage platform is made in an open grillwork
pattern to reduce resistance from the water and may include seats. Guides for
the descent line, several eyebolts for attaching tools, and steadying lines or
weights are provided. The frames of the stages may be collapsible for easy
storage. A safety shackle or screw-pin shackle seized with wire or with a cot-
ter pin must be used to connect the stage to the lifting line when raising or
lowering. Stages must be weight tested in accordance with PMS.
Stage Line. Used to raise and lower the stage, the stage line is to be 3-inch
double braid, or 3/8-inch wire rope minimum, taken to a capstan or run off a
winch and davit.
Diving Ladder. The diving ladder is used to enter the water from a vessel.
Weights. Cast iron or lead weights are used to weight the descent line.
Tool Bag. The tool bag is used to carry tools.
Stopwatches. Stopwatches are used to time the total dive time, decompression
stop time, travel time, etc.
8-7
SURFACE AIR SUPPLY SYSTEMS
The diver’s air supply may originate from an air compressor, a bank of high-pres-
sure air flasks, or a combination of both.
8-7.1
Requirements for Air Supply. Regardless of the source, the air must meet certain
established standards of purity, must be supplied in an adequate volume for
breathing, and must have a rate of flow that properly ventilates the helmet or
mask. The air must also be provided at sufficient pressure to overcome the bottom
water pressure and the pressure losses due to flow through the diving hose,
fittings, and valves. The air supply requirements depend upon specific factors of
each dive such as depth, duration, level of work, number of divers being
supported, and type of diving system being used.
8-7.1.1
Air Purity Standards. Air taken directly from the atmosphere and pumped to the
diver may not meet established purity standards. It may be contaminated by engine
exhaust or chemical smog. Initially pure air may become contaminated while
passing through a faulty air compressor system. For this reason, all divers’ air
must be periodically sampled and analyzed to ensure the air meets purity stan-
dards. Refer to Table 4-1 for compressed air purity requirements.
