(Note 3)

Horizontal mobility. Voice communications.

Support craft required. High rate of gas consumption.

Normal 300 fsw. Maximum: 380 fsw with CNO authorization.

MK 21 MOD 0 (Note 2)

Saturation diving search, salvage, and repair. Extensive bottom time.

21 (7 per watch) (Note 4)

Maximum diver safety. Bottom time efficiency. Maximum comfort. Continuous personnel monitoring.

Slow deployment. Large support craft and crew. Limited mobility. High rate of gas consumption.

Varies with DDS certification

MK 22 MOD 0 (Note 2)

Standby diver for PTC.

21 (7 per watch) (Note 4)

Collapsible for storage in PTC.

Slow deployment. Large support craft and crew. Limited mobility. High rate of gas consumption.

Varies with DDS certification


1. Surface-supplied deep-sea

2. Saturation UBA

3. Minimum personnel consists of topside support and one diver in the water

4. Varies according to manning requirements of deep dive system

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. 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. 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.

13-3.8 Operational Characteristics. Equipment operational characteristics are reviewed in Table 13-2 and specific equipment information can be found in paragraph 13-8.

All diving equipment must be certified or authorized for Navy use. Authorized equipment is listed in the NAVSEA/00C Authorized for Navy Use (ANU) list. For proper operation and maintenance of U.S. Navy approved diving equipment, refer to the appropriate equipment operation and maintenance manual.

13-3.9 Support Equipment and ROVs. In addition to the UBA, support equipment must not be overlooked. Items commonly used include tools, underwater lighting, power sources, and communications systems. The Coordinated Shipboard Allow ance List (COSAL) for the diving platform is a reliable source of support equipment. Commercial resources may also be available.

Occasionally, a mission is best undertaken with the aid of a remotely operated vehicle (ROV). ROVs offer greater depth capabilities with less risk to personnel but at the expense of the mobility, maneuverability, and versatility that only manned operations can incorporate.

13-3.9.1 Types of ROV. There are two types of ROVs, tethered and untethered. Tethered ROVs receive power, control signals, and data through an umbilical. Untethered ROVs can travel three to five times faster than tethered ROVs, but because their energy source must be contained in the vehicle their endurance is limited. ROVs used in support of diving operations must have ground fault interrupter (GFI) systems installed to protect the divers.

13-3.9.2 ROV Capabilities. Currently, much of the Fleet's requirements for observation diving are being met by using ROVs. They have been used for search and salvage since 1966. State-of-the-art ROVs combine short-range search, inspection, and recovery capabilities in a single system. A typical ROV system includes a control and display console, a power source, a launch and retrieval system, and the vehicle itself. Tethered systems are connected to surface support by an umbilical that supplies power, control signals and data. Untethered search systems that will greatly increase current search rates with extended endurance rates of 24 hours or more are currently under development. Figure 13-2 shows a typical NAVSEA ROV.

Figure 13-2. Remotely Operated Vehicle (ROV) Deep Drone.

13-3.10 Diver's Breathing Gas Requirements. In air diving, the breathing mixture is readily available, although pump and compressor capacities and the availability of back-up systems may impose operational limitations. The primary requirement for mixed-gas diving is that there be adequate quantities of the appropriate gases on hand, as well as a substantial reserve, for all phases of the operation. The initial determinations become critical if the nearest point of resupply is far removed from the operation site.

13-3.10.1 Gas Consumption Rates. The gas consumption rates and carbon dioxide absorbent durations for various types of underwater breathing apparatus are shown in Table 13-1. Refer to Chapter 4 for required purity standards.

13-3.10.2 Surface-Supplied Diving Requirements. For surface-supplied diving, the diver gas supply system is designed so that helium-oxygen, oxygen, or air can be supplied to the divers as required. All surface-supplied mixed-gas diving systems require a primary and secondary source of breathing medium consisting of helium-oxygen and oxygen in cylinder banks and an emergency supply of air from compressors or high-pressure flasks. Each system must be able to support the gas flow and pressure requirements of the specified equipment. The gas capacity of the primary system must meet the consumption rate of the designated number of divers for the duration of the dive. The secondary system must be able to support recovery operations of all divers and equipment if the primary system fails. This may occur immediately prior to completing the planned bottom time at maximum depth when decompression obligations are the greatest. Emergency air supply is provided in the event all mixed-gas supplies are lost.

13-3.10.3 Deep Diving System Requirements. A deep diving system must be able to store and supply enough gas to support saturation diving to the maximum certified depth. Deep diving systems can handle and store pure gases, and mix the required percentages of helium-oxygen as needed. When DDS-type equipment is employed, additional quantities of gas must be included for DDC and PTC charging and for replacing losses due to leakage, transfer trunk and service lock usage and scrubber cycling. A DDS must also have an air system capable of supporting surface-supplied air diving operations and initial pressurization of the DDS for saturation operations.

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