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.
15-3.1 Personnel Transfer Capsule. 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.
15-3.1.1 Gas Supplies. During normal diving operations, the divers' breathing and PTC gas are supplied from the surface through a gas supply hose. In addition, all PTCs
Figure 15-1. Typical Personnel Transfer Capsule Exterior.
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.
15-3.1.2 PTC Pressurization/Depressurization System. 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 depressur-ization. Depth gauges, calibrated in feet of seawater, monitor internal and external PTC depth. Equalization and vent valves are also provided for the access trunk.
15-3.1.3 PTC Life-Support System. The life-support equipment for the PTC includes carbon dioxide scrubbers, a gas supply to provide metabolic oxygen, oxygen, and carbon dioxide analyzers.
15-3.1.4 Electrical System. 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.
15-3.1.5 Communications System. A typical communications system is divided into four individual systems to ensure efficient operation under a variety of conditions.
■ 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.
■ 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.
■ Closed-Circuit Television (CCTV). The CCTV consists of video channels from the PTC to the MCC. Cameras are usually mounted outside the PTC.
■ 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.
15-3.1.6 Strength, Power, and Communications Cables (SPCCs). 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.
15-3.1.7 PTC Main Umbilical. The typical PTC main umbilical consists of a breathing-gas supply hose, a hot water hose, a pneumofathometer, and a strength member.
15-3.1.8 Diver Hot Water System. 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.
15-3.2 Deck Decompression Chamber (DDC). 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.
15-3.2.1 DDC Life-Support System (LSS). 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.
15-3.2.2 Sanitary System. 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.
15-3.2.3 Fire Suppression 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.)
15-3.2.4 Main Control Console (MCC). 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.
15-3.2.5 Gas Supply Mixing and Storage. The DDC gas system provides oxygen, helium-oxygen 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.
15-3.3 PTC Handling Systems. 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.
15-3.3.1 Handling System Characteristics. All handling systems have certain common characteristics. The system should:
■ Be adequately designed and maintained to withstand the elements and dynamic loads imposed by heavy weather.
■ Have the ability to control the PTC through the air-sea interface at sufficient speed to avoid excessive wave action.
■ Keep the PTC clear of the superstructure of the surface-support platform to avoid impact damage.
■ 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.
■ Include a handling system to move the suspended PTC to and from the launch/ retrieval position to the DDC.
■ Have a method of restraining PTC movement during mating to the DDC.
15-3.4 Saturation Mixed-Gas Diving Equipment. 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.
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