The configuration and the specific equipment composing a deep diving system
vary greatly based primarily on the type mission for which it is designed. Modern
systems however, have similar major components that perform the same functions
despite their actual complexity. Major components include a PTC, a PTC handling
system, and a DDC.
The PTC (Figure 15-1) is a spherical, submersible
pressure vessel that can transfer divers in full diving dress, along with work tools
and associated operating equipment, from the deck of the surface platform to their
designated working depth.
FIGURE 15-1 Typical Personnel Transfer Capsule Exterior.
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During normal diving operations, the divers’ breathing and PTC
gas are supplied from the surface through a gas supply hose. In addition, all PTCs carry emergency supplies of helium, helium-oxygen, and oxygen in externally
mounted flasks. Internal PTC pressure, gas supply pressures, and water depth are
continuously monitored from the PTC.
The typical helium system is designed to maintain PTC pressurization and purge
oxygen from all PTC electrical units to alleviate any fire hazard.
The helium-oxygen mixed-gas system consists of an internal built-in breathing
system (BIBS) with associated valves, piping, and fittings. The mixed-gas system
supplies emergency breathing gas to the diver umbilicals when the topside supply
is interrupted, and supplies the BIBS if the internal PTC atmosphere is
contaminated.
The gas supply and exhaust
system control and regulate internal PTC pressure. Relief valves and manual vent
valves prevent overpressurization of the PTC in case a line rupture causes a full
flask to discharge into the PTC. Needle valves are employed to control depressurization.
Depth gauges, calibrated in feet of seawater, monitor internal and external
PTC depth. Equalization and vent valves are also provided for the access trunk.
The life-support equipment for the PTC includes
carbon dioxide scrubbers, a gas supply to provide metabolic oxygen, oxygen, and
carbon dioxide analyzers.
The electrical system uses a multiple voltage distribution
system that may be used for heating, internal and external lighting, instrumentation,
and communications. Power for normal PTC operation is surface-supplied
and is transmitted through power and communications cables. A battery supplies
critical loads such as atmosphere monitoring, emergency CO2 scrubber, and
communications if the surface-supplied power is interrupted.
A typical communications system is divided into four
individual systems to ensure efficient operation under a variety of conditions.
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Hardwire Intercom System. The intercom system is an amplified voice system
employing a helium speech unscrambler providing communications within the
PTC and between the Main Control Console (MCC), divers, deck winch operator,
Deck Officer, and the DDCs.
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Underwater Mobile Sound Communications Set (UQC). The UQC system is a
wireless emergency system providing voice communications between the PTC
and underwater telephone system of the attending ship. The UQC system is
used if the power and communications cables fail or are disconnected.
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Closed-Circuit Television (CCTV). The CCTV consists of video channels from
the PTC to the MCC. Cameras are usually mounted outside the PTC.
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Sound-Powered Phones. The PTC is equipped with a sound-powered phone
system for communication with the MCC in case the normal system is lost.
The strength, power,
and communications cables typically provide electrical power, wired communications,
instrumentation signals, a strength member, and coaxial transmission
(CCTV signals) between the MCC and the PTC.
The typical PTC main umbilical consists of a breathing-gas
supply hose, a hot water hose, a pneumofathometer, and a strength member.
Hot water may be necessary when conducting saturation
dives. The surface ship supplies hot water via the PTC main umbilical to the
diver’s suit and breathing gas heater. The PTC operator monitors the water
temperature and ensures that the flow is adequate.
Hot water may be necessary when conducting saturation
dives. The surface ship supplies hot water via the PTC main umbilical to the
diver’s suit and breathing gas heater. The PTC operator monitors the water
temperature and ensures that the flow is adequate.
The DDC furnishes a dry environment
for accomplishing decompression and, if necessary, recompression. The DDC is a
multi-compartment, horizontal pressure vessel mounted on the surface-support
platform. Each DDC is equipped with living, sanitary, and resting facilities for the
dive team. A service lock provides for the passage of food, medical supplies, and
The DDC furnishes a dry environment
for accomplishing decompression and, if necessary, recompression. The DDC is a
multi-compartment, horizontal pressure vessel mounted on the surface-support
platform. Each DDC is equipped with living, sanitary, and resting facilities for the
dive team. A service lock provides for the passage of food, medical supplies, and other articles between the diving crew inside the chamber and topside support
personnel.
The DDC Life Support-System maintains the
chamber environment within acceptable limits for the comfort and safety of the
divers. The typical system consists of temperature and humidity control, carbon
dioxide removal, and equipment monitoring. Processing consists of filtering
particulate matter, removing carbon dioxide and gaseous odors, and controlling
heat and humidity.
The sanitary system consists of hot and cold water supplies for
operating the wash basin, shower, and head. Waste from the head discharges into a
separate holding tank for proper disposal through the support platform’s collection,
holding, and transfer system.
All DDCs have fire-fighting provisions ranging from
portable fire extinguishers to installed, automatic systems. DDCs and recompression
chambers have similar hyperbaric flammability hazards. Ignition sources and
combustion materials should be minimized during critical fire zone times. (At the
normal operating depth of PTCs, the oxygen concentration will not support
combustion, so they have no built-in fire-fighting equipment.)
The MCC is a central control and monitoring area.
The MCC houses the controls for the gas supply and atmosphere analysis for the
DDC, atmosphere monitoring for the PTC, pressure gauges for gas banks, clocks,
communications systems controls, recorders, power supplies, and CCTV monitors
and switches for the DDC and PTC.
The DDC gas system provides oxygen, heliumoxygen
mixtures, helium, and air for pressurization and diver life support. A BIBS
is installed in every lock for emergency breathing in contaminated atmospheres, as
well as for administering treatment gas during recompression treatment. Normal
pressurizing or depressurizing of the DDC is done from the MCC. A means of
sampling the internal atmosphere is provided for monitoring carbon dioxide and
oxygen partial pressure. An oxygen-addition system maintains oxygen partial
pressure at required levels. A pressure-relief system prevents overpressurization of
the chamber.
A DDS should be outfitted with gas-mixing equipment, commonly referred to as a
“Mixmaker,” which provides additional flexibility when conducting deep saturation
diving. The Mixmaker can provide mixed gas at precise percentages and
quantities needed for any given dive. If necessary, the gas coming from the
Mixmaker can be sent directly to the divers for consumption.
Of all the elements of DDS, none are more varied than
PTC handling systems. Launch and retrieval of the PTC present significant
hazards to the divers during heavy weather and are major factors in configuring
and operating the handling system.
All handling systems have certain common
characteristics. The system should:
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Be adequately designed and maintained to withstand the elements and
dynamic loads imposed by heavy weather.
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Have the ability to control the PTC through the air-sea interface at sufficient
speed to avoid excessive wave action.
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Keep the PTC clear of the superstructure of the surface-support platform to
avoid impact damage.
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Have lifting capability of sufficient power to permit fast retrieval of the PTC,
and controls and brakes that permit precision control for PTC mating and
approach to the seafloor.
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Include a handling system to move the suspended PTC to and from the launch/
retrieval position to the DDC.
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Have a method of restraining PTC movement during mating to the DDC.
The UBA MK 21 MOD 0 is an open
circuit, demand-regulated diving helmet designed for saturation, mixed-gas diving
at depths in excess of 300 fsw and as deep as 950 fsw (Figure 15-2). With the
exception of the demand regulator, it is functionally identical to the UBA MK 21
MOD 1, which is used for air and mixed-gas diving. The regulator for the MK 21
MOD 0 helmet is the Ultraflow 500, which provides improved breathing resistance
and gas flow over the MK 21 MOD 1.
The UBA MK 22 MOD 0 is an open circuit, demand-regulated, band-mask
version of the UBA MK 21 MOD 0 (Figure 15-3). It is used for the standby diver
for saturation, mixed-gas diving at depths in excess of 300 fsw and as deep as 950
fsw. It is provided with a hood and head harness instead of the helmet shell to
present a smaller profile for storage.
FIGURE 15-2 MK 21 MOD 0 with Hot
Water Suit, Hot Water Shroud, and Come-
Home Bottle.
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FIGURE 15-3 MK 22 MOD 0 with Hot
Water Suit, Hot Water Shroud, and Come-
Home Bottle.
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