The tugs will work for the state owned oil company Statoil and the process plant operator Gassco on delivery in the third quarter of 2013. They are 35m long stern drive azimuth thruster tugs with a broad 15.4m beam and a bollard pull of about 65 tonnes.
The design was developed by Buksér og Berging together with Marin Design and is a break through for Rolls-Royce Bergen gas engines in the tug market, and for the new US35 thrusters in escort tugs. The unique engine performance characteristics in terms of response time, fuel consumption and low methane played an important role in the customer’s decision to choose Rolls-Royce as their preferred supplier.
Two 1,705kW Bergen C26:33 6cyl in-line gas engines will provide the power. They will drive two US35 azimuth thrusters of the latest design, through a mechanical transmission. Rolls-Royce will also provide its Acon control system and monitoring for the gas system together with propulsion system engineering, and the AGA Cryo single LNG tank plus gas supply based on two coldboxes.
The system is designed for weekly bunkering intervals and bunkering time is estimated to be 45 minutes. Vetle Sverdrup, Commercial Director at Buksér og Berging AS said: “We wanted to base the design of the new tugs on the spark ignition lean burn engine concept, and the ability to accommodate direct drive in addition to a low emission profile.
The propulsion system on high performance escort tugs needs to accommodate rapid load pick up over the entire load range. Due to these factors we chose to work closely with Rolls-Royce on this project.” The tugs are being built in Turkey by Sanmar Marine.