CHAPTER 8 — Surface-Supplied Air Diving Operations
Change A 8-5
1.
Calculate minimum manifold pressure (MMP).
Round up to 223 psig
2.
Calculate standard cubic feet (scf) of air available. The formula for calculating
the scf of air available is:
Where:
Pf
=
Flask pressure = 3,000 psig
Pmf
=
Minimum flask pressure = 200 psig
MMP =
223 psig
FV
=
Floodable Volume of flask = 8 scf
N
=
Number of flasks = 4
3.
Calculate scf of air required to make the dive. You will need to calculate the air
required for the bottom time, the air required for each decompression stop, and
the air required for the ascent. The formula for calculating the air required is:
Where:
D
=
Depth (fsw)
1.4
=
Consumption rate in acfm needed per diver from Table 8-2
N
=
Number of divers
T
=
Time at depth (minutes)
Bottom time: 30 minutes
Decompression stops: A dive to 130 fsw for 30 minutes requires the following
decompression stops:
3 minutes at 20 fsw
MMP psig
(
)
0.445D
(
)
165 psig
+
=
0.455
130
(
)
165 psig
+
=
222.85 psig
=
scf available
Pf
Pmf
MMP
+
(
)
–
14.7
-----------------------------------------------
FV
N
=
scf available
3000
200
223
+
(
)
–
14.7
-----------------------------------------------
8
4
=
5609.79 scf (round down to 5600)
=
scf required
D
33
+
33
----------------
1.4
N
T
=
scf required
130
33
+
33
---------------------
1.4
3
30
=
622.36 scf
=
