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ROV's FOR BEGINNERS
Deployment
When I think of deployment systems for ROV's I feel a chill down my spine, I
have for years been involved in specifying ROV deployment Systems. I can still
today not get any of my colleagues to agree to what Certifying standards the
Deployment Winch and Crane / A-Frame should be made to.
The approach of many ROV manufacturers in the past was that the ROV
Purchaser get their own custom made Deployment System, this is getting
increasingly difficult since the Certifying standards used is not always what
the Rule book states but what individual companies or even individuals within
some companies set.
The AODC has some guidelines but these are not always up to date and since
the Deployment equipment is accepted on a contract to contract basis this can be
difficult to keep track of.
Now back to the subject heading, the different deployment methods used by
different companies and manufacturers vary but there are a few common methods
that have proved successful.
The different methods and necessary equipment will briefly be discussed
below:
Live boating with soft Kevlar reinforced Umbilical
For live boating operations with a larger ROV you normally use an Umbilical
winch to manage the ROV Umbilical connecting the ROV with the Surface Control
Unit. The Winch unit is not capable of lifting the ROV out of the water, this is
achieved by using a recovery line that has previously been attached to the ROV
and Umbilical and the actual lifting is done by using a ship based Lifting
Crane. The lifting gear has to be certified as standard onshore lifting
equipment.
The Umbilical can be as long as 10,000 feet or more common is for it to be
around 1,500 feet.
Live boating with Steel armoured Umbilical
For live boating operations with a larger ROV using a Steel Armoured
Umbilical and a winch to manage the ROV Umbilical are connecting the ROV with
the Surface Control Unit. The Winch unit is capable of lifting the ROV out of
the water, this is achieved by using a large sheave wheel attached and suspended
on the end of a ship based Lifting Crane. The sheave wheel can alternately be
fitted to a lifting A-frame over the side or stern of the ship. I have
previously used a Hemp sock over the Steel Armoured Umbilical near the ROV to
prevent it from Bird Caging.
The lifting gear has to be certified as standard onshore lifting equipment.
The Umbilical can be as long as 5,000 feet or more common is for it to be
around 3,000 feet.
Live boating with Steel armoured Umbilical and a Tether Management System
For live boating operations with a larger ROV using a Steel Armoured
Umbilical and a winch to manage the ROV Umbilical are connecting the ROV with
the Surface Control Unit. The Winch unit is capable of lifting the ROV out of
the water, this is achieved by using a large sheave wheel fitted to a lifting
A-frame over the side or stern of the ship. The Tether Management System can
normally provide a soft Tether Cable with a length of up to 200 meters.
The Tether Management System is fitted to the end of the Steel Armoured
Umbilical and can be described as an underwater winch for managing the soft
tether cable.
The advantages of this method of operating the ROV is that the ROV does not
have to rely on its's own propulsion to get down to working depth or seabed. The
TMS ROV provides a base from which the ROV can move laterally up to the length
of the fitted soft tether cable.
The lifting gear has to be certified as standard onshore lifting equipment.
The Umbilical can be as long as 5,000 feet or more common is for it to be
around 3,000 feet.
Live boating with Steel armoured Umbilical and a Powered Tether Management
System
Operations with a larger ROV using a Steel Armoured Umbilical and a winch to
manage the ROV Umbilical connecting the ROV with the Surface Control Unit. The
Winch unit is capable of lifting the ROV out of the water, this is achieved by
using a large sheave wheel fitted to a lifting A-frame over the side or stern of
the ship. The Tether Management System can normally provide a soft Tether Cable
with a length of up to 200 meters. In some operations the sea currents
experienced are very strong to overcome this a propulsion and control system can
be fitted to give the Tether Management System and ROV the facility to get
closer to the work site then what is possible without the extra propulsion power
of the Tether Management System.
The advantages of this method of operating the ROV is that the ROV does not
have to rely on its's own propulsion to get down to working depth or seabed. The
TMS ROV provides a base from which the ROV can move laterally up to the length
of the fitted soft tether cable.
The lifting gear has to be certified as standard onshore lifting equipment.
The Umbilical can be as long as 5,000 feet or more common is for it to be
around 3,000 feet.
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