On the "USS MONITOR" saturation dives

Abstract

The USS Monitor was an irconclad warship from the american civil war which
sunk on 12/31/1862 @ Cape Hatteras, some 14 miles off the coast of
North Carolina to ca. 235 feet. By a joint project of USN, NOAA,
Global Industries and many others it was partly recovered in an epic
effort in 2001 & 2002. One of the main technologies used was
saturation diving with Heliox. Here, we re-calculate the decompression phase
of the SAT-dives along the USN SAT procedure from 2018 and compare with
COMEX / MT92 and NORMAM-15 procedures.

Full text

1
On the „USS Monitor“
saturation dives
03.03.2023
Miri Rosenblat, TAU
Nurit Vered, Technion Haifa
Albi Salm, SubMarineConsulting
DOI:

2
On the „USS Monitor“
saturation dives
03.03.2023
Abstract:
The USS Monitor was an irconclad warship from the american civil war which
sunk on 12/31/1862 @ Cape Hatteras, some 14 miles off the coast of North
Carolina to ca. 235 feet. By a joint project of USN, NOAA, Global Industries
and many others it was partly recovered in an epic effort in 2001 & 2002. One
of the main technologies used was saturation diving with Heliox. Here, we re-
calculate the decompression phase of the SAT-dives along the USN SAT
procedure from 2018 and compare with COMEX / MT92 and NORMAM-15
procedures.
Introduction: slide # 3
Methods: slides # 4  6
Result: slide # 7
Data: slides # 8  10
Discussion: slide # 11
References: slides # 12  14
Historical Note: slide # 15

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On the „USS Monitor“ saturation dives
Introduction:
The USS Monitor was an irconclad warship from the
american civil war which sunk on 12/31/1862 @ Cape Hatteras, some 14
miles off the coast of North Carolina to ca. 235 feet [4], [5].
By a joint project of USN, NOAA, Global Industries and many others it was
partly recovered in an epic effort in 2001 & 2002 [1], [2] & [3].
One of the main technologies used was saturation diving (SAT diving),
i.e. the dive time / bottom-time being substantially longer than 72 h.
The utilized gas is called “Heliox”, a breathing gas consisting only of Helium
and Oxygen.
Here, we re-calculate the decompression phase of the SAT-dives along the
USN SAT procedure from 2018 [6] and compare with others like the french
COMEX / MT92, or the brazilian NORMAM-15 procedures for Heliox
saturation diving and an older USN SAT procedure from the 1991 manual.
To facilitate the handling of all these procedures, the latest BETA version,
issued 01.03.2023, of a freeware/shareware tool [7] was used.

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On the „USS Monitor“ saturation dives
Methods (1):
The USN SAT decompression procedure is described in-depth
in [6], chapter 13 on pp. 13-1 (p. 651)  13-42 (p. 692).
The here relevant SAT decompression rates are in Table 13-9, p. 686:
The unlimited duration excursions are found in the tables 13-7 (down: p. 679)
and 13-8 (up: p. 680).

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On the „USS Monitor“ saturation dives
Methods (2):
The relevant data for working pressure / storage depth and the
excursion depths are taken from various sources and compared.
From [1], [2] and Captain Chris Murray‘s description in [3] and [5], p. 157
we have the following:
storage depth / working pressure: 180 fsw
excursions to Monitor working site: 230 up to 245 feet
total decompression time: 66 h
In [4] we found marginally different values on p. 18 but with a similar
decompression time of 66 h.
The TTS (time-to-surface, i.e.: the sum of: travel time for excursion, hold time
2h, travel time from storage depth) was evaluated along Table 13-9 and then
compared with the TTS of the other procedures, the breathing mix
of Heliox and the pO2 being pretty much the same on all exposures.

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On the „USS Monitor“ saturation dives
Methods (3):
N.B.:
the storage depth / working pressure of 180 fsw is a pressure,
also the entries in Tables 13-7 & 13-8.
For decompression calculations to be comparable, normally a geometric
length, the depth of the dives, is used. Thus we applied the tabulated
conversion factors of the USN manual Table 2-10, [6], on p. 2-33:
i.e.: 1 fsw @ 15 °C  0.312616 m of fresh water column.
Thus 180 fsw  56.27 m FW.
For all practical purposes in the SI-system for the other SAT-procedures
we used 57 m as storage depth and 75 m as the maximal downward
excursion depth.
On the usage of the various pressure units, pls. cf. as well [8].

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On the „USS Monitor“ saturation dives
Results:
(*) downward excursion depth: 240 fsw / 75 m
then: upward excursion back to 180 fsw in 31 min, hold time 2 h
travel time from storage to 0 fsw: 45.7 h  61.7 h incl. stop times
pls. cf. DATA(3) on slide # 10.
(**) pO2 : 0.6 Bar & 0.5 Bar
Procedure Ref. # TTS
[hours]
USN, documented [1], [2] 66
USN 2018, storage pressure 180 fsw (*) [6] 64.5
USN 2018, storage pressure 180 fsw [6] 62.09
USN 1991, storage pressure 180 fsw [7] 78.3
MT 92 / COMEX, storage depth 57 m [7] (**) 46.5  50
NORMAM-15, storage depth 57 m [7] 60.8

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On the „USS Monitor“ saturation dives
Data (1):
MT92 / COMEX,
NORMAM-15
&
USN 1991
procedures
for
comparison.

9
On the „USS Monitor“ saturation dives
Data (2):
Pure Traveltime: 46 h  i.e.: complete TTS = 62 h

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On the „USS Monitor“ saturation dives
Data (3):
downward excursion depth: 240 fsw / 75 m
upward excursion to 180 fsw in 31 min, hold time 2 h
travel time from storage to 0 fsw: 61.69 h
complete TTS: 0.5 h + 2 h + 62 h = ca. 64.5 h

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On the „USS Monitor“ saturation dives
Discussion:
The TTS of the real dives and the USN 2018 procedures fall
in line pretty much; the USN 1991 procedure interestingly enough with the
longest TTS!
As it is clear from the output (DATA(1) & DATA(3)), the TTS depends basically
on the pO2 and if upward excursions are allowed resp. the subsequent hold-
times.
The swiss SAT-table on Air has never been used as such due to too high
a pO2 & pN2 whereas the Heliox tables have TTS by far to short. As the
experts from the field have put it that time: [9], p. 739 ff: (citation:) "Hannes
Keller ... and this approach did not become popular with commercial divers ..
because ... the risk of severe DCS.“ And there: [10], p. 364, " ... it appears
that during early development in the 1960s, helium and multiple inert gas
schedules were short and used a great deal of oxygen (see, e.g. Keller &
Bühlmann 1965). But in recent years have become longer and use less
oxygen as the emphasis in the industry has shifted from speed to safety.“
(The emphasis above is ours.) Amen!

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On the „USS Monitor“ saturation dives
References (1):
[1] FACEPLATE:
The Official Newsletter for the Divers and Salvors of the United States Navy
Volume 5, No. 4 / September, 2001, p. 1 & 13, 14 & 16.
[2] FACEPLATE:
The Official Newsletter for the Divers and Salvors of the United States Navy
Volume 6, No. 2 / November, 2002, p. 1  6 & 18. The Download site there:
https://www.navsea.navy.mil/Home/SUPSALV/00C3-Diving/Faceplate-
Magazine/
[3] NOAA: https://oceanexplorer.noaa.gov/explorations/explorations.html
[4]  [163] Clancy, Paul (2013) Ironclad, The Epic Battle, Calamitous Loss
and Historic Recovery of the USS Monitor, Koehlerbooks, N.Y., ISBN 978-1-
938467-11-0
[5]  [169] Broadwater, John D. (2012) USS Monitor: A historic Ship
completes its final Voyage, Texas A&M University Press, ISBN-13: 978-1-
60344-474-3, ISBN-10: 1-60344-474-2

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On the „USS Monitor“ saturation dives
References (2):
[6] U.S. Navy Diving Manual, Revision 7, CHANGE A 30 APRIL 2018
Download free of charge: http://www.divetable.eu/15.pdf
[7] DIVE Version 3_11, download free of charge from the beta test site:
https://www.divetable.info/beta/index_e.htm
The handbook / related documentation for the RELEASE versions there:
https://www.divetable.info/DIVE_V3/V3e/index.htm
[8] Rosenblat, M. Vered, N. Salm, A. (02.02.2023) The diving medical
detectives: when diving medicine books are completely wrong,
Part V: On pressure units
DOI: 10.13140/RG.2.2.31827.45600

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On the „USS Monitor“ saturation dives
References (3):
[9]  [178] Edmonds, Carl; Bennett, Michael et al.(2016) Diving and
Subaquatic Medicine, Fifth Edition, CRC Press; ISBN 978-1-4822-6012-0
[10]  [203] Bennett, Peter B., Elliott, David H.(eds.) (1982) The Physiology
and Medicine of Diving, Third Edition, Best Publishing Co, San Pedro, CA,
ISBN: 0-941332020
#####################################
Hint: the number in brackets  [ … ] points to our list of useful books @:
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On the „USS Monitor“ saturation dives
Historical Note:
Just for comparison with the historical, experimental swiss tables:
DEEP DIVING RESEARCH LABORATORY
DEPARTMENT OF INTERNAL MEDICINE
UNIVERSITY HOSPITAL ZURICH
For a saturation to 60 m we have the following TTS:
Breathing
Mix:
Bottom
internal
CODE
No.:
Breathing
Mix:
deco
Breathing
Mix:
deco O2
TTS
[hours]
Air 27 6 h 47
Heliox10 28 Air: 20 h 23
Heliox10 30 Air: 10 h 5 h 18