Principles Of Operation

The U.S. Navy closed-circuit mixed-gas UBA is a constant partial-pressure-of-oxygen rebreather. To conserve the gas supply and extend underwater duration, the efficiency of gas use is improved by:

Removing carbon dioxide produced by metabolic action of the body. Adding pure oxygen to the breathing gas to replace the oxygen consumed. Recirculating the breathing gas for reuse.

Figure 17-1. MK 16

MOD 0 Closed-Circuit Mixed-Gas UBA.

Figure 17-1. MK 16

MOD 0 Closed-Circuit Mixed-Gas UBA.

EXHALATION M0UTHPIECE

HOSE

ASSEMBLY

TO CENTER SECTION

TO SECONDARY DISPLAY

OXYGEN ADDITION VALVE.

DILUENT BYPASS VALVE-

DILUENT HIGH' PRESSURE INDICATOR

DILUENT BOTTLE VALVE

EXHALATION M0UTHPIECE

HOSE

ASSEMBLY

TO CENTER SECTION

TO SECONDARY DISPLAY

OXYGEN ADDITION VALVE.

DILUENT BYPASS VALVE-

-CHECK VALVE

, OXYGEN L-BYPASS VALVE

OXYGEN 'INLINE FILTER

OXYGEN HIGH PRESSURE INDICATOR

DILUENT HIGH' PRESSURE INDICATOR

DILUENT BOTTLE VALVE

OXYGEN • BOTTLE VALVE

DILUENT REGULATOR

OXYGEN REGULATOR

DILUENT BOTTLE PRIMARY BATTERY

-CHECK VALVE

, OXYGEN L-BYPASS VALVE

OXYGEN 'INLINE FILTER

OXYGEN HIGH PRESSURE INDICATOR

OXYGEN • BOTTLE VALVE

DILUENT REGULATOR

OXYGEN REGULATOR

DILUENT BOTTLE PRIMARY BATTERY

Figure 17-2. MK 16 MOD 0 UBA Functional Block Diagram.

17-2.1 Recirculation and Carbon Dioxide Removal. The diver's breathing medium is recirculated in a closed-circuit UBA to remove carbon dioxide and permit reuse of the inert diluent and unused oxygen in the mixture. The basic recirculation system consists of a closed loop that incorporates inhalation and exhalation hoses and associated check valves, a mouthpiece or full face mask (FFM), a carbon dioxide removal unit, and a diaphram assembly.

17-2.1.1 Recirculating Gas. Recirculating gas is normally moved through the circuit by the natural inhalation-exhalation action of the diver's lungs. Because the lungs can produce only small pressure differences, the entire circuit must be designed for minimum flow restriction.

17-2.1.2 Full Face Mask. The FFM uses an integral oral-nasal mask or T-bit to reduce dead space and the possibility of rebreathing carbon dioxide-rich gas. Similarly, check valves used to ensure one-way flow of gas through the circuit must be close to the diver's mouth and nose to minimize dead space. All breathing hoses in the system

T< 'WHJ

Figure 17-4. Underwater Breathing Apparatus MK 16 MOD 0.

Figure 17-4. Underwater Breathing Apparatus MK 16 MOD 0.

requiring a deep operational capability should allow frequent opportunity for training, ensuring diver familiarity with equipment and procedures. Workup dives are strongly recommended prior to diving at depths greater than 130 fsw. MK 16 diver qualifications may be obtained only by completion of the MK 16 Basic Course (A-431-0075) or the Naval Special Warfare Center MK 16 qualifications course. MK 16 qualifications remain in effect as long as diver qualifications are maintained in accordance with Military Personnel Manual article 1410380. However, a diver who has not made a MK 16 dive in the previous six months must refamiliarize himself with MK 16 EPs and OPs and must complete a MK 16 training dive prior to making a MK 16 operational dive. Prior to conducting MK 16 decompression diving, a diver who has not conducted a MK 16 decompression dive within the previous six months must complete open water decompression training dives. Refer to Table 17-1 for the personnel requirements for MK 16 diving operations.

17-4.1 Operating Limitations. Using combat swimmer multilevel dive (CSMD) procedures provides SPECWAR divers with the option of conducting multiple-depth diving with the MK 16 UBA if a maximum depth of 70 fsw (NEDU Report 13-83) is not exceeded at any time during the dive. Refer to Table 17-2 for equipment depth limitations. Diving Supervisors must also consider the limiting factors presented in the following paragraphs when planning closed-circuit UBA operations.

17-4.1.1 Oxygen Flask Endurance. In calculating the endurance of the MK 16, only the oxygen flask is considered. The endurance of the oxygen flask is dependent upon the following:

■ Flask floodable volume

Table 17-1. Personnel Requirements Chart for Mixed-Gas Diving.

Mixed-Gas UBA Dive Team Optimum

Minimum

Designation

One Diver

Two Divers

One Diver

Two Divers

Diving Officer

(Notes 3, 4)

(Notes 3, 4)

(Notes 3, 4)

(Notes 3, 4)

Diving Medical Officer

(Note 5)

(Note 5)

(Note 5)

(Note 5)

Diving Supervisor

1

1

1 (Note 2)

1 (Note 2)

Diver

1

2

1

2

Standby Diver

1 (Note 7)

1 (Note 7)

1 (Note 7)

1 (Note 7)

Diver Tender

1 (Note 1)

2 (Note 1)

1 (Note 1)

1 (Note 1)

Standby Diver Tender

1

1

(Note 8)

(Note 8)

Timekeeper/Recorder

1

1

EBS Operator

(Note 6)

(Note 6)

(Note 6)

(Note 6)

Total Personnel Required

6

8

4

1. One tender per diver when divers are surface tended. If using a buddy line, one tender is required for each buddy pair.

2. May act as timekeeper/recorder.

3. EOD Diving Officer is required on site for all EOD operations that involve render safe procedure; for SPECWAR, Diving Officer is not required on station. On station is defined as at the dive location.

4. Diving Officer may perform any other function simultaneously (i.e., Diving Officer/Diver).

5. A Diving Medical Officer is required on station for all dives exceeding the normal working limit.

6. EBS Operator is for MK 16 in-water decompression dives.

7. At the Diving Supervisor's discretion, the standby diver shall be fully dressed with the exception of scuba or MK 16, mask, and fins. These items shall be ready to don.

8. If the Standby Diver is deployed, the Diving Supervisor shall tend the Standby Diver.

Table 17-2. Equipment Operational Characteristics.

Diving

Maximum Working Limit (fsw)

Chamber

Equipment

(Notes 1 and 2)

Requirement

MK16 UBA

150 (air diluent)

Note 3

200 (HeO2 diluent)

Note 3

Notes:

1. Depth limits are based on considerations of working time, decompression obligation, oxygen tolerance and nitrogen

narcosis. The expected duration of the gas supply, the expected duration of the carbon dioxide absorbent, the adequacy of

thermal protection, or other factors may also limit both the depth and the duration of the dive.

2. A Diving Medical Officer is required on station for all dives exceeding the normal working limit.

3. Dives deeper than the normal working limits require a recompression chamber on station. On station is defined as at the

dive location.

■ Initial predive pressure

■ Required reserve pressure lazy-shot lines. Lines shall be marked with red and yellow or black bands starting at the diver(s) or clump end. Red bands will indicate 50 feet and yellow or black bands will mark every 10 feet.

17-4.2.5 Diver Marker Buoy. Diver marker buoys will be constructed to provide adequate visual reference to monitor the divers location. Additionally, the amount of line will be of sufficient length for the planned dive profile.

17-4.2.6 Depth Gauge/Wrist Watch. A single depth gauge and wrist watch may be used when diving with a partner and using a distance line.

17-4.3 Recompression Chamber Considerations. A recompression chamber and a Diving Medical Officer are not required on station (on station is defined as at the dive location) as prerequisites for closed-circuit UBA diving operations, unless the dive(s) will exceed the maximim working limit. However, the following items should be determined prior to beginning diving operations:

Location of the nearest functional recompression chamber. Positive confirmation of the chamber's availability in case of emergency should be obtained.

Location of the nearest available Diving Medical Officer if not at the nearest recompression chamber.

Location of the nearest medical facility for treatment of injuries and medical problems not requiring recompression therapy.

The optimal method of transportation to the treatment chamber or medical facility. If coordination with other units for aircraft/boat/vehicle support is necessary, the Diving Supervisor shall know the telephone numbers and points of contact necessary to make these facilities available as quickly as possible in case of emergency. A medical evacuation plan should be included in the Diving Supervisor brief. Preparing an emergency assistance checklist similar to that in Chapter 6 is recommended.

17-4.4 Diving Procedures for MK 16.

17-4.4.1 Employing a Single, Untended EOD Diver. Generally, it is safer for divers to work in pairs rather than singly. However, to do so when diving on underwater influence ordnance doubles the diver bottom time expended, increases the risk to life from live ordnance detonation, and increases the risk of detonation caused by the additional influence signature of the second diver. The EOD Diving Officer may authorize the employment of a single, untended diver when it is deemed that the ordnance hazard is greater than the hazard presented by diving alone. All single, untended divers must use a full face mask (FFM). The EOD Diving Officer or Diving Supervisor shall consider the following factors when deciding whether to operate singly or in pairs:

Experience of the diver Confidence of the team

Type and condition of ordnance suspected

■ Environmental conditions

Degree of operational urgency required

17-4.4.2 Simulated Training Scenarios. Simulated ordnance training scenarios do not constitute a real threat, therefore single untended divers shall not be used in training operations. The diver shall be surface tended or marked by attaching a buoy to him.

17-4.4.3 EOD Standard Safety Procedures. The following standard safety procedures shall be observed during EOD diving operations:

■ An EOD Diving Officer shall be on scene during all phases of an explosive ordnance disposal diving operation involving a Render Safe Procedure (RSP).

■ When diving on unknown or influence ordnance, the standby diver's equipment shall be the same type as the diver neutralizing the ordnance.

17-4.4.4 Diving Methods. Diving methods include:

■ Single Marked Diving. Consists of a single diver with FFM marked with a lightweight buoyant line attached to a surface float. Upon completion of a dive requiring decompression, the diver will signal the diving supervisor that he is ready to surface. The diving boat will then approach the surface float and recover the diver.

■ Paired Marked Diving. Procedures for paired marked diving are identical to the procedures for a single marked diver, but with the addition of the second diver connected by a buddy/distance line.

at the setpoint during normal activity at a constant depth (the oxygen-addition valve operation on the MK 16 cannot be heard).

Secondary Display. Check the secondary display frequently (every 2-3 minutes) as outlined in the MK 16 O&M manual (paragraph 3-4.6.2) to ensure that all sensors are consistent with the primary display and that plus and minus battery voltages are properly indicating.

■ High-Pressure Indicators. Check the oxygen- and diluent-pressure indicators frequently as outlined in the MK 16 O&M manual (paragraph 3-4.6.3) to ensure that the gas supply is adequate to complete the dive.

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