Liquid-cooled dynamic positioning at Havila multi-field standby vessel
Vacon drive controlling dynamic positioning
Rolls-Royce Marine* has designed a completely new vessel type, the UT527, a so called multi-field standby vessel (MFSBV). The UT527 type of vessels will operate as emergency rescue response vessels as well as first-line oil recovery vessels to minimize spills. The 140-metre long vessel is also able to undertake fire fighting operations.
This new vessel type was specially designed for Havila Supply** to meet the needs of their specific contract closed with Norsk Hydro Produksjon. Operating on the Troll and Oseberg fields in the North Sea, this mulfi-field standby vessel is also designed to be capable of remaining on location in all weather conditions and to be seaworthy at all times, meeting the necessary requirements of the Norwegian Maritime Directorate (NMD) in this respect.
Azimuth thruster in control
On the Havila Troll, the first UT527 to set sail, a liquid-cooled Vacon NX drive with a power of 1.5 MW is controlling the azimuth thruster used for dynamic positioning of the vessel. Azimuth thruster stands for a propulsor consisting of a propeller that can be rotated around a vertical shaft.
Dynamic positioning (DP), in turn, is essential in vessels sailing in deep waters and harsh environments, and a necessity e.g. in oil collecting. Dynamic positioning stands for the use of systems which automatically control a vesselīs position and heading via thruster commands e.g. to keep the vessel at a fixed location. Enabling precision manoeuvring, tracking and other specialist positioning abilities, dynamic position relies on operational efficiency. Consequently, it places a high reliability requirement on equipment, operators and vessel managers.
Controlling the azimuth thruster by a drive brings many benefits. Speed control according to demand brings considerable energy savings and decreases electro-mechanical stress for the electrical system and provides flexibility in power generation and distribution.
The load tolerances of Vacon drives are well within the approved limits, and robust designs protect the equipment against vibration and humidity in the harsh environment.
Vaconīs Norwegian partner, Scandinavian Electric Systems, was responsible for system integration.
Low noise and vibration levels as requirement
When designing the UT527, special attention has been focused on conditions onboard to secure as low levels of noise and vibration as possible in all permanent accomodations.
This goal is strengthened by the choice of the drive: a liquid-cooled drive has a low noise level, as no large fan or any additional air conditioning or filtered ventilation systems are required.
Optimal liquid cooling solution
Vacon NX drives are built around hardware and software modularity. The liquid-cooled NX uses the same control module as the air-cooled NX, but has a power section especially optimized for liquid cooling. This contrasts with the liquid-cooled drives of many other manufacturers, which are based on air-cooled drives with a redesigned cooling element.
In the liquid-cooled NX, all components requiring cooling are mounted on one or more aluminium cooling elements. The entire power range can be produced with only six different chassis sizes.
The same mechanical units are used for both AC and DC inverters. The cooling liquid, which can be pure drinking water, removes about 95 per cent of the heat generated.
Liquid-cooled Vacon drives offer major benefits in cooling efficiency as the heat loss can be dissipated outside the installation area. Another important advantage is a compact design that allows space savings of up to 70 per cent compared with air-cooled drives. This is particularly beneficial on ships and vessels with limited space.
On the Havila, a liquid-cooled Vacon NX with a power of 1500 kW is controlling the Azimuth thruster used for dynamic positioning of the vessel. Controlling the azimuth thruster by a drive brings many benefits. Speed control according to demand brings considerable energy savings and decreases electro-mechanical stress for the electrical system and provides flexibility in power generation and distribution.
*Rolls-Royce is a world leader in marine propulsion, engineering and hydrodynamic expertise with a broad product range and systems integration capability.
** North Sea oil and gas industry has ordered multi-field standby vessels against a 10-year contract from Norsk Hydro Produksjon to be delivered to the North Sea Oil and Gas industry.