EoW May 2009

EuroWire – May 2009

technical article

Abstract

The Deep-Sea ROV cable has changed the

world of deep-sea exploration forever. With

this technology, explorers and historians

have been able to investigate the interiors

of such shipwrecks as the Titanic and the

Bismarck. This unique cable has been used

as a communications link between the

operator and two specially designed ROVs

(Remote Operated Vehicle) referred to as

the Deep-Sea ROV and the Hybrid AUV

(Autonomous Underwater Vehicle)/ROV.

This cable is 900microns in diameter

and carries a single fibre for sending

information to and from the fibre optic

telemetry system.

Mike Cameron of Dark Matter LLC originally

developed this technology in 1999. Mike

Cameron and his brother James Cameron

used this ROV technology in documentary

films before Oceaneering International

purchased the technology in January

2005. Oceaneering has plans of bringing

this technology into the mainstream

by utilising both of the ROV’s unique

capabilities, for potential uses such as

the inspection of undersea equipment,

port security monitoring, and search and

rescue missions.

The Oceaneering ROVs are revolutionary

and have created a paradigm shift in ROV

design. The two ROVs are self-contained

units that house their own batteries for

power and spool out their own cable for

communications.

A typical ROV sends power and commands

through a large tether, which restrains the

path of the vehicle and how far the vehicle

can penetrate into a wreck.

In addition, the tether is commonly

spooled out from the command centre via

a very large reel. Since the fibre optic tether

is expendable, the Oceaneering ROVs have

the unique capability of running into one

opening and out through another with no

restrictions on entry and exit points and no

restrictions on depth of penetration into a

cavity. The Deep-Sea ROV cable gives these

ROVs a competitive edge.

The cable spools out by way of a

proprietary mechanical payoff system

built into the ROV itself, eliminating

the need for a fibre optic slip ring. The

Deep-Sea ROV contains approximately

600metres while the Hybrid AUV/ROV

contains 2,000metres of this very fine

900micron cable.

This cable contains one optical fibre,

speciality strength members, and oil. The

optical fibre is a typical single mode fibre

255microns in diameter, utilised for controls

and feedback. The strength members aid in

both tension control and cable durability.

The oil gives the cable its incompressible

properties at depths of up to 6,100metres

(20,000 feet). The outer jacket is a special

polymer blend used to achieve the correct

buoyancy of the cable in the water column.

The ROVs are so small, and contain so

much cable, that an improperly weighted

cable would wreak havoc on an ROV’s

buoyancy controls.

This cable was qualified using both

standard testing practices and distinctively

new test methods. Mechanical and

environmental performance was tested

and the cable was subjected to the most

severe requirements of three different

standards.

The three standards were the ANSI/ICEA

S-87-640-2006, the GR-20-CORE, and the

EN 187105. To get a better idea of the

performance of this cable, it was tested

to failure under the general guidelines of

the specifications.

In addition, several custom tests were

developed in order to predict the reliability

of the cable. A specialised hydrostatic

pressure test bench was employed by

Oceaneering in order to simulate the

pressure on the cable at extreme ocean

depths. A buoyancy requirement was also

created by Oceaneering in order to achieve

the proper buoyancy. A specialised test

for hockling (the marine term for kinking)

was created by CommScope in order to

benchmark the hockle performance of

each cable. From these test results we

could assure Oceaneering the best possible

cable for their special application.

1 Introduction

The Deep-Sea ROV cable was evaluated by

both the manufacturer and the end user

for two different but similar applications.

This specialised cable was already being

used for the Deep-Sea ROV, but needed to

be optimised to perform well in a newer

application.

This new application was a Hybrid AUV/

ROV with both autonomous and normal

ROV capabilities. Many cabling trials,

laboratory tests and field tests were

conducted in order to hone in on the

proper cable design.

2 Cable design

2.1 Customer request

Oceaneering had requested a new cable

design containing only one fibre and

with a diameter close to 900microns. This

invention was a 3

generation Deep-Sea

ROV cable.

2.1.1 First generation cable

The first generation cable was a 2-fibre

cable consisting of two multimode fibres

with an overall diameter of approximately

1.4mm. One fibre was for information sent

to the ROV (to control the ROV) and the

other was information sent back from the

ROV (live video feedback).

This cable contained many ends of strength

elements for increased tensile strength.

Later on, the Oceaneering team replaced

the fibre optic systems so that they could

send information bi-directionally via a

single fibre rather than two separate ones.

2.1.2 Second generation cable

Still maintaining the same diameter for

mechanical compatibility, this second

generation cable contained only a single

fibre.

The cable was still 1.4mm in diameter but

added an additional jacket of protection. In

between the two jacket layers was a layer

of strength elements for added tensile

strength and abrasion resistance.

Deep-Sea ROV Cable

Jarrett S Shinoski Research & Development, CommScope Claremont, NC; Dave Weaver and Tom Tolman Oceaneering International Inc, Hanover, MD