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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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Copyright 1995 DCF
Last Updated
23/03/03