17-12 Change A
U.S. Navy Diving Manual—Volume 4
MK 16 gas endurance =
Where:
FV
=
Floodable volume of flask in cubic feet
PI
=
Initial Pressure in psia
PR
=
Reserve Pressure in psia
VO2 =
Oxygen consumption in medical scfm (32°F)
T1
=
Ambient air temperature in °R
T2
=
Coldest water temperature expected in °R
Rankine conversion factor:
°R
=
°F + 460
All pressure and temperature units must be absolute.
17-4.1.1.5
Example. The endurance of a MK 16 MOD 0 UBA charged to 2,500 psig for a
dive in 50° F water when the ambient air temperature is 65° F would be computed
as follows:
This duration assumes no gas loss from the UBA during the dive and only
considers metabolic consumption of oxygen by the diver. Divers must be trained
to minimize gas loss by avoiding leaks and unnecessary depth changes. Clearing a
flooded face mask is a common cause of gas loss from the UBA. When a full face
mask (FFM) is used, gas can pass from the UBA breathing loop into the FFM and
escape into the surrounding seawater due to a poor face seal. Leaks that continue
unchecked can deplete UBA gas supply rapidly. Additionally, during diver ascent,
the dump valve opens to discharge breathing gas into the surrounding water,
thereby preventing overinflation of the breathing diaphragm. Depth changes
should be avoided as much as possible to minimize this gas loss.
17-4.1.2
Diluent Flask Endurance. Under normal conditions the anticipated duration of
the MK 16 diluent flask will exceed that of the oxygen flask. The MK 16 diluent
bottle holds approximately 21 standard cubic feet (595 liters) of gas at a stored
pressure of 3,000 psig. Diluent gas is used to maintain the required gas volume in
the breathing loop and is not depleted by metabolic consumption. As the diver
descends, diluent is added to maintain the total pressure within the recirculation
system at ambient water pressure. Loss of UBA gas due to offgassing at depth
FV
P1
T2
T1
------
PR
–
VO2
14.7 psi
-------------------------------------------
492
T2
---------
MK 16 gas endurance
0.1
2
514.7
,
510
525
(
)
514.7
–
[
]
0.049
14.7
-----------------------------------------------------------------------------
492
510
---------
=
258 minutes
=
