Our innovative splash zone concept is based on a magnetic crawler, together with our developed navigation system.
In 2012, we participated in an offshore operation where the task was to install a 6inch blind plug into a sea chest on the FPSO.
From the construction vessel, a normal Work Class ROV needed to fly to the FPSO, and install the small plug 4 meters below the waterline.The operation took place during November, in the harsh North Sea environment.
Due to the buoyancy of the ROV; the maneuver of the vehicle was almost impossible due to waves and surface sea current. A weather limit of 2.0m Hs
was required for the operation, and significant HSE measurements were taken to protect the ROV from collision with the hull. Almost 10 days the construction vessel with a crew of 55 persons, had to wait for proven weather conditions.
Back at the office, surprised at the challenges that these beforehand seemingly simple plug operations had presented, we started to look for new solutions.
A way to challenge not only the Law of Archimedes,but also some of the general principles of Physics and Hydrodynamics.
Four years later, the result is presented in the form of the NorHull Vehicle.
A complete work class crawler that is able to interface familiar ROV tools, but on a unique kind of platform. Operated from a single 20” container, deployed in 4.5m Hs weather.
Offshore classification and survey is today conducted using ROV systems launched from a support vessel or direct from the installation/FPSO.
The same system is used for other subsea support tasks like thruster replacement, hull inspection, turret inspection, sea chest blinding, CP measurements, anode installation and other light construction work.
Due to the buoyancy element of the ROV, a normal system has limitation to work in the challenging splash zone, and require normally weather limits to be approx. 2.0m Hs. Heave and sea current worsen these limits.
The concept was to develop an Autonomous Crawler, which by the force of permanent magnets, attaches itself on a metal surface, and traverses autonomously with minimal user input, according to a pre-planned map.
This presents a tremendous advantage in all areas where a traditional WROV would be employed, as it is independent of weather conditions. Especially in the splash-zone, where the buoyancy of the WROV would cause great instability.
In addition, the autonomous nature of the Crawler allows it to propagate on a metal surface with minimal input from the operator, performing tasks such as maintenance, or cleaning.
The NorHull Vehicle
The Norhull technology is a generic permanent magnetic traction vehicle, remotely operated by umbilical from a topside control station, to be used as a platform for project/client specific tools and equipment in the splash-zone on mobile and fixed offshore installations.
The unit is fixed to any steel hull with 3.5T permanent magnetic force, that can be adjusted. The idea was to develop an innovative tool that can perform detailed survey of hulls, cleaning and light construction work like sea chest plug installation, etc. in the challenging splash zone. As a part of the development, UWILD inspections has been planned for, so that these can be done offshore during operation of the drilling unit.
The overall aim of the vehicle design has been to:
- Add client value by providing safe and efficient intervention services in near-surface and splash-zone on a wide range of offshore structures.
- Provide longer weather-windows for splash-zone intervention projects, by introducing a “fixed” tool vehicle (fixed meaning no relative motions between tool and structure).
- Add client value by carrying out near surface intervention tasks without using expensive offshore vessel spreads (launched from client facility)