CHAPTER 8 Surface-Supplied Air Diving Operations
Change A 8-7
MK 20 MOD 0
The MK 20 MOD 0 is a surface-sup-
plied UBA consisting of a full face
mask, diver communications compo-
nents, equipment harness, and an um-
bilical assembly (Figure 8-2). One of its
primary uses is in enclosed spaces, such
as submarine ballast tanks. The MK 20
MOD 0 is authorized for use to a depth
of 60 fsw with surface-supplied air and
must have an Emergency Gas Supply
when used for enclosed space diving.
Operation and Maintenance. Safety
considerations and working procedures
are covered in Chapter 6. NAVSEA
SS600-AK-MMO-010 Technical Man-
ual, Operations and Maintenance In-
struction Manual is the technical man-
ual for the MK 20 MOD 0. To ensure
safe and reliable service, the MK 20
MOD 0 system must be maintained and
repaired in accordance with PMS pro-
cedures and the MK 20 MOD 0 opera-
tion and maintenance manual.
Air Supply. Air for the MK 20 MOD 0 system is supplied from the surface by
either an air compressor or a bank of high-pressure flasks as described in para-
EGS Requirements for MK 20 MOD 0 Enclosed-Space Diving. In order to ensure
a positive emergency air supply to the diver when working in a ballast tank, mud
tank, or confined space, an Emergency Gas Supply (EGS) assembly must be used.
As a minimum, the EGS assembly consists of:
An adequately charged ANU approved scuba cylinder with either a K- or J-
An approved scuba regulator set at manufacturers recommended pressure, but
not lower than 135 psi, with an extended EGS whip 50 to 150 feet in length. If
the diving scenario dictates leaving the EGS topside, adjust the first stage reg-
ulator to 150 psig.
An approved submersible pressure gauge.
The scuba cylinder may be left on the surface and the EGS whip may be married
to the divers umbilical, or it may be secured at the opening of the enclosed space
being entered. The diver may then enter the work space with the extended EGS
whip trailing. The second stage regulator of the EGS is securely attached to the
Figure 8-2. MK 20 MOD 0 UBA.