Buksér og Berging to build world’s first LNG tugs

They will fulfil the towage contract recently announced by the oil and gas company Statoil ASA, to serve the Karsto gas processing plant on behalf of operator Gassco (MJ – Towlines January 2012).

Sanmar Denizcilik AS has been entrusted with the construction of the new vessels in their new yard in Tuzla Bay, Istanbul, with delivery scheduled for late in 2013.

The tugs have been designed in house by Buksér og Berging, in cooperation with Marin Design AS of Kolvareid, Norway. Project partners Rolls-Royce Marine (Norway) have signed a contract to deliver highly efficient engines and propulsion systems for the vessels. The project was developed in close contact with Rolls-Royce, giving them a unique opportunity to understand and adhere to the operational requirements.

Robert Løseth, Rolls-Royce, Senior VP – Merchant, Propulsion Systems and Engines said, “This is a breakthrough for our Bergen gas engines and cutting edge propulsion technology. The choice our customer has made highlights the industry leading engine performance, fuel consumption and low methane emissions that Rolls-Royce can offer, which is now being applied to tugs. ”

Rolls-Royce will supply two Bergen C6 Ing engines, two Aquamaster US35 propulsion units, RR Acon control and monitoring equipment for the gas system, and one AGA Cryo LNG tank with an LNG system based on two coldboxes. The Bergen gas fuelled engines can operate on low load without any restriction, have a very quick and stepless ramp up time from 0 to 100% load, and are easy to service and maintain.

The LNG system is designed by AGA Cryo and integrated with the Rolls-Royce propulsion system. This single tank LNG system has full gas redundancy approved by NMD (Norwegian Maritime Directorate) ie; no diesel back up is required. The fuel system is designed for weekly bunkering to be carried out by the tug crew and takes approximately 45 minutes.

The operational benefits of a gas fuelled propulsion system are a cleaner engine room, less waste oil and no ‘switch over’ problems. Environmental benefits with Spark Ignition gas engines incorporated in the new design are:
• 92% reduced NOx emission
• 17% reduced GHG emission
• 98-100% reduced SOx emission
• 98% reduced particulates
• Compliant with Tier III regulations

Buksér og Berging AS commercial director Vetle Sverdrup said, “We wanted to base the design of the new tugs on the spark ignition lean burn engine concept, with 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.”

It is anticipated that the new hull and propulsion system will achieve up to 20% higher thrust efficiency, compared to standard escort tug designs, and achieve a bollard pull of at least 65 tons. The tugs will have an overall length of 38.00m, a beam of 14.50m and draft of 7.50m, with accommodation for five persons. In addition to escort duties and shiphandling, the tugs will be equipped for fire fighting and pollution control duties.