CHAPTER 17 Closed-Circuit Mixed-Gas UBA Diving
Change A 17-29
When addition of oxygen to the UBA is manually controlled, ppO2 should be
maintained in accordance with techniques and emergency procedures listed in the
MK 16 O&M manual.
The Diving Supervisor and medical personnel should recognize that a diver who
has been breathing a mixture with ppO2 lower than 0.6 ata for any length of time
may have a greater risk of developing decompression sickness. Such a diver
requires observation after surfacing, but need not be treated unless symptoms of
decompression sickness occur.
Emergency Breathing System (EBS). The Emergency Breathing System pro-
vides an alternate breathing source for decompressing diver(s) in the event of a
MK 16 failure. The two types of EBS available for use are EBS Type I and EBS
Type II MK 1 Mod 0. The systems have been designed and tested as an accurate
method for topside to control and monitor breathing gas being supplied to a
diver(s) during decompression. The EBS shall be deployed whenever MK 16 de-
compression diving is anticipated. In the event of MK 16 failure or malfunction,
the diver(s) will transfer to the EBS as soon as possible and continue to use the
EBS to complete the decompression profile. It is to be used only for its designed
purpose as discussed in paragraph 17-10.3 as an emergency breathing source and
not as a surface-supplied diving system.
EBS Type I. The EBS type I was designed and is intended to be used only in
support of diving up to 200 fsw. NAVSEA Operation and Maintenance manual
S9592-AN-MMO-010 provides detailed equipment descriptions, reference data,
and information on operation and maintenance. This type of EBS is a non-certified
system (Figure 17-8)
EBS Type II MK 1 Mod 0. The EBS II is a certified surface-supplied, in-water
emergency life-support system, with capabilities to support two divers during
decompression for dive profiles to 300 fsw (Figure 17-9). The EBS II enables
voice communication capabilities between topside personnel and divers while the
divers are using the MK 24 FFM (Figure 17-10). PEO MINEWAR technical
manual SS600-AL-MMA-010 provides detailed equipment descriptions, reference
data, and information on operation and maintenance.
Required Gas Supply for the EBS. When a decompression dive is planned, the
Diving Supervisor must calculate the volume of gas required should a diver be
required to breathe from the EBS throughout decompression.
Calculating EBS Gas Requirements. The following steps may be used to calcu-
late EBS gas requirements (Figure 17-11):
Determine decompression profiles from appropriate closed-circuit mixed-gas
UBA decompression tables using 0.7 ata constant partial pressure of oxygen.
Multiply the time of each decompression stop by the gas consumption rates
(scfm) in Table 17-11 to obtain total volume required per stop. Table 17-11
assumes a light work rate (gas consumption = 0.63 acfm).