RO/RO Gets Novel LNG Bunkering Solution

LNG tanks

By Wendy Laursen 2015-06-08 18:58:58

Dale Emmerton, National Marine Manager at Australia’s SeaRoad Shipping, has come up with an innovative LNG bunkering concept for his RO/RO newbuilding that has turned the eyes of the world towards Australia.

Like in most ports, there is no direct infrastructure for refuelling LNG where the new vessel will call, so locally available LNG will be bunkered by loading LNG road tank trucks directly onto the vessel during normal loading operations.

The design features three LNG road tankers connected to a permanent fuel manifold on the ship. They will be changed out after every round voyage for three tankers that will have been filled the previous day at the local LNG plant. The tankers will be secured to the vessel in special loading bays on the weather deck, aft, with multiple twist-locks.

This process is a relatively simple logistic task, particularly when compared to bunkering heavy fuel oil. “LNG as the primary fuel was chosen with an eye to both the present and the future,” says Emmerton. “Currently our ships burn heavy fuel oil which is sourced overseas and imported into Melbourne by a single company for resale and delivery to the vessels. LNG is available locally from multiple sources and is seen as a more reliable and certainly cleaner energy source.”

He further explains: “Our eye to the future involved both the stability of supply and also the very strong likelihood that Australia will join other developed countries in banning the use of heavy fuel oil in the coastal waters where our vessels will exclusively trade. Australia has significant reserves of natural gas which should ensure security of supply into the future.”

Teamwork

Steel cutting for the new ship is expected to start in Germany’s Flensburger Schiffbau-Gesellschaft (FSG) shipyard in September 2015, and DNV GL is providing full classification services and liaising with Australia’s Maritime Safety Authority on its statutory requirements.

The project began back in 2008, says Timothy Holt, Area Manager Australia & New Zealand for DNV GL – Maritime. Having won the tender for the groundbreaking project, Holt’s enthusiasm led to a meeting of the SeaRoad Shipping team with a group of engineers in Oslo led by Torill Grimstad Osberg. The team conducted risk assessments and eventually granted Approval in Principle for the concept. 

“Initially, I think we can safely say, our idea was met with dismay around the industry,” says  Emmerton. “At that stage all the development and rules were being based on large permanent tanks fitted below deck, but our local DNV GL surveyor was most supportive. Our method simplified the task of bunkering compared to conventional methods and made it much safer. This was quickly understood by the team in Høvik, and after the initial meeting, the DNV GL team was very quick to assist with solutions for achieving our idea. The rest of the story is history with the various codes and rules now taking into account portable-type tanks for short-haul, quick-turnaround ships.”

Safety

The risk assessment led to the incorporation of a number of safety features to ensure appropriate levels of stability and fire safety. Heavier cargo units than an LNG tank would normally be secured by four twist-locks, however the gas tanks will have six.

The tanks take three cargo slots on deck, but the LNG piping system has no effect on cargo capacity. There are two main parts to the system, cryogenic and non-cryogenic. The cryogenic part includes the flexible pipes connecting the fuel tanks to a common manifold that feeds the LNG to a deck-mounted gas handling room where waste heat from the machinery plant is used to convert the -160 ºC liquid into a gas in specially designed heat exchangers. 

The cryogenic pipes have to be stainless steel and double-walled because of the very low temperatures. Once the liquid has been heated and converted to gas, the piping is simpler but still requires ducts that are vented and monitored for potential leaks.

When the gas reaches the engine room it is supplied to the engines via gas valve units which regulate the gas pressure according to power demand. “The uniqueness of the design means we had to go through a detailed approval process with DNV GL to take care of all the rules and regulations which are not yet 100 per cent established with respect to the draft IGF Code,” says Raimon Strunck, Vice President Sales at FSG.

The Cargo Mix

“The cargo mix has driven the design, because SeaRoad wants double-stack cassettes for shipping of containers on the main deck, a mix of trailers and cars in the lower hold and LNG trailers on the weather deck,” says Strunck. There is also a specially designed area for the transport of livestock. “An-other cargo-related design driver is the fact that we have dangerous goods cargo in the forward part of the weather deck and, right behind it, reefers. This is rather unusual and normally not allowed due to explosion risks, but together with DNV GL we have found a design solution that ensures that this can be done safely and in compliance with class rules.”

The vessel’s principal dimensions are 182 meters length overall, 26.6 meters beam and a maximum draught of 6.3 meters. Service speed will be 20 knots. The vessel’s stern ramp is a split design to enable loading and unloading of two decks simultaneously. The design will streamline operations for truck drivers. 

The newbuild will be twin-screw, powered by two MaK dual-fuel engines rated at 7.2 megawatts each. Two MaK gensets of 2.5 megawatts each will be installed to give the ship 100 per cent electrical power redundancy, something that is critical considering the schedule that the vessel will keep and the high-value cargo that it will carry. “The main engines and auxiliaries are dual-fuel and the auxiliaries are unusually large for a RoRo, double the size in fact,” says Strunck. 

The newbuild is expected to commence service in late 2016.