CHAPTER 17 Closed-Circuit Mixed-Gas UBA Diving
Change A 17-19
tactical equipment, etc.) are available, and that the UBA functions properly before
allowing the divers to enter the water. Appropriate check lists to confirm proper
functioning of the UBA are provided in the MK 16 O&M manual.
WATER ENTRY AND DESCENT
The maximum descent rate is 60 feet per minute. During descent, the UBA will
automatically compensate for increased water pressure and provide an adequate
volume of gas for breathing. During descent the oxygen partial pressure may
increase as oxygen is added to the breathing mixture as a portion of the diluent.
Depending on rate and depth of descent, the primary display on the MK 16 UBA
may illuminate flashing green. It may take from 2 to 15 minutes to consume the
additional oxygen added by the diluent during descent. While breathing down the
ppO2, the diver should continuously monitor the primary and secondary display
until the ppO2 returns to setpoint level.
General Guidelines. The divers shall adhere to the following guidelines as the
dive is conducted.
Failure to adhere to these guidelines could result in serious injury or
Monitor primary and secondary display frequently (every 2-3 minutes)
Wear adequate thermal protection
Know and use the proper amount of weights for the thermal protection worn
and the equipment carried
Check each others equipment carefully for leaks at the start of the dive
Do not exceed the UBA canister duration and depth limitations for the dive
Minimize gas loss from the UBA (avoid mask leaks and frequent depth
changes, if possible)
Maintain frequent visual or touch checks with buddy
Be alert for symptoms suggestive of a medical disorder (paragraph 17-11)
Use tides and currents to maximum advantage
At Depth. If the UBA is performing normally at depth, no adjustments will be
required. The ppO2 control system will add oxygen from time to time. Monitor
UBA primary and secondary displays and high pressure gauges in strict accor-
dance with the MK 16 O&M manual. Items to monitor include: