About the power and data cables and
connectors of the diving umbilicals
The article "Will Bio-Inspired Underwater Vehicles With Artificial
Intelligence Replace Divers?", published in May 2024 in the Food for
Thought section of this website, argues that rather than replacing
divers with machines equipped with artificial intelligence, the
appropriate policy would be to enable them to work in symbiosis with
these machines. As a result, commercial diving companies need to
find or develop the necessary tools to achieve that capability. For this
reason, implementing diver monitoring systems, such as those
previously described in a dedicated article in this section, in addition to
SONAR and heads-up displays in divers' helmets, appears to be an
essential approach many commercial divers have long envisaged.
Therefore, it is pleasing to learn that the US Navy shares a similar
approach and that the company Coda Octopus, headquartered at 3300
S Hiawassee Road #104-105 Orlando, USA, has developed for them
the "Diver Augmented Vision Display System (DAVD)", which is now
available to commercial diving companies.
However, the installation of such a system, which provides the diver
with sonar images, graphics, navigation maps, and augmented and
virtual reality, in addition to the camera, sonar images, hot water
temperature (when used), and other information that needs to be sent
to the diving supervisor, requires a suitable power and data
transmission system compact enough to allow easy handling and
designed to avoid interference, so the diver and diving supervisor are
provided with untainted information at all times during the dive.
That opens a discussion on the evolution of data transmission cables
and connectors and why choosing some systems over others is
appropriate when purchasing new umbilicals.
The problems associated with providing voice communication and light
to divers at work have been persistent since the early days when
these essential tools were first adopted and installed. For example, the
pictures below, taken from the 1924 US Navy Manual, which is available
along with others in the "Historical Diving" subsection of the
"Documents" section, illustrate how communications were designed
100 years ago.
Air supply
Life line + telephone
The telephone cable was integrated into the lifeline. The electrical
conductors formed the core of the assembly, with the rest of the
structure acting as a lifeline and protection for the conductors. The
telephone cable connection was positioned at the back of the helmet
(see #10 below), and the assembly cable/lifeline was curved to pass
under the diver's arm (see picture above) and be secured on the top
part of the harness or to the helmet, thereby providing sufficient
flexibility for the telephone cable not to pull on the connection directly.
Note that the lifeline was separate from the rubber air hose, which
was not used to pull the diver as it was not strong enough for that
purpose.
It should be noted that underwater lights during the 1920s were not
mounted on divers' copper helmets. Instead, they were separate units,
typically powered by 6 or 12 volts of direct current (DC). Divers would
install these lights in their immediate proximity to effectively illuminate
their working area.
In the 1970s and 1980s, the development of the offshore diving
industry led to a new generation of helmets made from composite
materials and equipped with lights and cameras. These advances
provided divers with greater safety and freedom (lead shoes were
replaced by fins or rubber boots, and helmets became lighter and
more neutrally buoyant) and allowed the dive supervisor to better
monitor and assist the diver.
This led to the addition of two cables to the communications cable,
which were secured with the lifeline along the air (or heliox) hose (see
below). The disadvantage of such a design is that the diver's umbilical
can easily become entangled when diving in cluttered areas, such as
inside platforms or wrecks, as the cables and lifeline are seldom held
perfectly along the air hose, resulting in loops that various objects can
easily catch. In addition, the additional cables reduce the flexibility and
weigh down such umbilicals, increasing their diameter and making
them more prone to being dragged along by underwater currents.
Blue: Air hose Yellow: Pneumo hose
Red: Communication cable Orange: Video cable
Grey: Light supply cable White: Life line
The reason for using separate cables was that, while DC power is not
inherently a source of interference, the potential for electromagnetic
interference (EMI) and crosstalk increases when power and signal
cables are close together. This can degrade the quality of video and
communication signals. Proper cable management and shielding
techniques, which were unavailable then, should be used to mitigate
these risks. Consequently, with the technology available, it was
generally advisable to avoid grouping DC power cables with video and
communication signal cables.
The picture below, taken from the US Navy Manual Revision 6, shows
that such umbilicals were still used by the US Navy in 2008.
Additionally, note that some equipment suppliers still sell them.
Considering that the previously discussed "Diver Monitoring Systems"
are useful tools some clients and states request to be in place or may
require in the near future, in addition to the advantages offered by the
Diver Augmented Vision Display System (DAVD), which should be added
to the Diver Monitoring System, as mentioned in the article "Will Bio-
Inspired Underwater Vehicles With Artificial Intelligence Replace
Divers? ", published in May 2024 in the Food for Thought section of
this website, the best choice is to adopt a cable grouping power
supplies and data transfer when purchasing a new umbilical, even if
some of the connections it provides are not intended to be used at the
time of the transaction. Additionally, while it is acceptable for
conservative individuals to purchase modern umbilicals with the
previous two-cable design, old-designed umbilicals, which have their
lifeline and cables kept along the rubber air hose using tapes, should
be definitively banned for the reasons previously explained.
Also, as suggested above, connectors are essential parts of the power
supply and data transfer line as they should be fully waterproof, not
prone to disconnection, and allow for the perfect isolation of each
connection. In this regard, reports on the Coda Octopus Diver
Augmented Vision Display System (DAVD) indicate that it uses a
connector from the "micro-circular series" developed by SubConn
(https://www.macartney.com/connectivity/subconn/), which allows
signals and power supplies to be combined in a single connector and
secured by a “locking sleeve”, as shown in the drawing below
illustrating this series.
It should be noted that two types of communication links were and are
still used:
•
Four-wire communication cables allow the installation
of duplex communications, enabling all
parties connected to the system to talk
and listen simultaneously. They were
preferably connected by mash marine-types
connectors for an extended period. However, many umbilical
manufacturers today prefer connectors equipped with a “locking
sleeve” that prevents accidental disconnection.
•
Two-wire communication cables do not provide the advantages of
the four-wire system, as the diver and the supervisor use the
same line to send and receive messages. They were, and still are,
often connected to the helmet via two
specific screws secured on the shell.
Although the main advantage of this
design is its simplicity, it exposes the
wires to water that climbs along them
by capillarity, resulting in corrosion and
the need to cut the extremity of the cable periodically.
For this reason, waterproof connectors should be preferred.
.
The development of the diving and ROV industries has resulted in a
new generation of umbilicals being offered to divers since the late
eighties, with the establishment of well-known companies such as
Cortland Fibron and Umbilicals International. This new generation of
umbilicals is typically constructed from a combination of more robust
and durable materials than the rubber previously used. The primary
materials include high-strength synthetic fibers such as Kevlar or
Aramid, which provide excellent tensile strength and abrasion
resistance. The outer sheath is often made from polyurethane or other
tough polymers to provide protection against physical damage and
environmental factors.
As a result, they are strong enough to support the diver's weight,
eliminating the need for a safety line, and the depth gauge hose and
various cables have been twisted along the main gas hose in the
manufacturing plant to form a single piece, eliminating the need for
taping. Technical advances have also made it possible to combine the
communication and video wires into the same cable. However, the
power supply for the light remains separate, resulting in two cables
installed along the air supply hose (if the umbilical is designed to
supply a helmet light).
The grouping of wires with several functions in the same cable
requires the installation of a "pigtail", where the different wires are
bundled together to supply the devices to which they are dedicated.
Extensions with connectors, preferably models with a locking sleeve to
keep them in place, are installed to connect the camera and
communications (see figure below). The pigtail construction process
uses special rubber compounds designed to withstand harsh
underwater conditions. The construction process involves pouring the
rubber into moulds to form the desired shapes, which are then cured
to achieve the required strength and flexibility. Kits are sold to create
custom moulded components on site when the original pigtail needs to
be replaced.
This type of umbilical is sold by many manufacturers, such as Divex
(https://www.jfdglobal.com/products/commercial-divers-
equipment/surface-supply/divex-diver-umbilicals/). However, a more
advanced design of cables is now available from some manufacturers
that combine all the power and data wires into one cable.
Manufacturers such as Novasub, a company based in the Netherlands
(https://www.novasub.com/product-categorie/cables-umbilicals/),
offer these advanced designs, with some cables offering up to 20
wires. These are, of course, the cables suitable for systems such as
the Diver Augmented Vision Display System (DAVD), which require a mix
of data and power cables, and the diver monitoring systems that are
today mandatory in some countries such as Norway and with some
clients. The section below of the Novasub DLR-CAT6-12C24 shows that
the 20 cores are contained in a cable with a diameter of 12.6 mm,
which is consistent for installation on a diver's umbilical.
Please note that SubConn is an American brand under the MacArtney
Group (https://www.macartney.com/), a Danish company specializing in
underwater technology solutions, which is listed with many other
manufacturers on our website in the "Power and Data Connectors and
Cables" subsection of the "Diving Equipment Manufacturers &
Suppliers" section within the "Logistics" main section. This sub-section
can be accessed by clicking on the button below.
Note: the dimensions are in mm
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