'JSFTBGFUZBQQSPWBMGPSXPSMEnT GJSTUNFUIBOPMQPXFSFETIJQ Stena Germanica, the world’s first ship in commercial operation running on methanol, is approved after SP Fire Research performed risk assessment and design of the fire safety based on SOLAS II 2/17 “Alternative design and arrangements”. Although methanol has long been handled with traditional fire protection in cargo pump-rooms on tankers, a deeper understanding of the fuel called for a new approach to achieve sufficient fire safety. STENA GERMANICA is a so-called “ro-pax” ferry, bringing vehicles and passengers across the Baltic Sea. As of 1st January 2015 this area together with the North Sea and the English Channel is a Sulphur Emission Control Area (SECA) where stricter sulphur emissions regulations apply. Similar restrictions apply around the coasts of North America and several more areas are planned around the world for the future. The new requirements have posed serious challenges for shipping companies and demanded new technological solutions, including use of alternative fuels and exhaust gas treatment. Many shipping companies have chosen to make use of Liquefied Natural Gas (LNG) to meet the requirements and avoid flue gas treatment. The same is achieved using methanol, but for this fuel the transportation and storage is far less complicated, both on the ship and ashore. Furthermore, there is a great benefit with methanol in the possibility to make it renewable from biomass in large scale in the future. Therefore Stena chose methanol for the Stena Germanica when it came to complying with the new regulations. Regulatory framework for low flashpoint fuels Flashpoint is the lowest temperature at which a fuel can be ignited; if the temperature is lower the fuel will not vaporize a sufficient amount of fuel gases. The flashpoint of methanol is far from as low as of LNG or gasoline but still lower than what is permitted by the international ship fire safety regulations in SOLAS (Safety Of Life At Sea). An international code under SOLAS on safety for ships using gases and other low-flash- point fuels (the IGF Code) is under development. However, until such a code is ratified the only regulatory way forward is to show equivalent safety through SOLAS regulation I/5 or II- 2/17. These regulations provide openings for alternative design and arrangements for fire safety but require that safety is not compromised. A fire risk assessment was therefore carried out for the Stena Germanica to demonstrate how the particularities of methanol would be managed to assure that fire safety was not adversely affected. It was performed by SP Fire Research as part of a large technical methanol conversion project at Stena and involved classification society Lloyd’s Register, engine manufacturer Wärtsilä and ship designer ScandiNaos as key partners. Beyond traditional fire protection In the first steps of the fire risk assessment it became clear that not only fire hazards associated with the lower flashpoint have to be considered for alternative fuels, even if this may be the only deviation. What is thereby addressed is generally the increased probability that flammable vapours of a low flashpoint fuel will accumulate and possibly ignite in case of a leakage. However, it is not sufficient to only minimize the probability of leakage and ignition. A sound fire safety design must, as any regulatory framework, address all levels of fire safety. In the fire risk assessment, fire detection and fire extinguishment were also identified as areas in need of further investigation. For example, how is detection and localization achieved when a methanol fire does not show visible flames or produce smoke? And how is extinguishment performed when the fuel in addition to the low flashpoint also has wide flammability limits and bound oxygen? These questions went beyond traditional fire protection and required further analysis. Bunker tank, pump room and fuel piping installations It was decided that the ship should be designed at least as safe as a conventional ship in each affected area of fire safety. To manage this, a number of risk control measures were added. For example, all fuel piping was designed double walled and butt-welded. The only space where methanol is managed in single walled pipes is the pump room. Here a robust drainage system was designed and the equipment used is suitable for explosive environment (ATEX). Furthermore, a smart gas detection system was designed automated with the ventilation and the pump system; if methanol is detected the ventilation is increased and if a high level of methanol is detected, though still far below the flammability limit, the 700 bar methanol transfer to the engines is stopped. An automatic seamless transition is then made to run on diesel only and the methanol pipes are flushed with nitrogen. The methanol storage tank is kept in a constantly inert state with nitrogen to avoid a combustible atmosphere. Furthermore, the tank will be surrounded by water on all sides, seawater and permanent ballast water tanks, which will directly neutralize the miscible fuel in case of a leakage. Bunker tanks at the bottom of the ship thus allow safe and efficient storage. Detection and localisation becomes crucial as FEATURE: 1&--&54t4)*11*/(t-0(*45*$4 Photo courtesy Stena Line
Bioenergy International no 7 December 2015
To see the actual publication please follow the link above