We have heard many companies are looking at using alternative fuels, Navigator Gas uses alternative fuels now. Some of our engines use LNG and we have now converted a ship to use ethane as fuel.

Why do we think ethane is a good source of fuel?

Marcus Hook in the USA is an major export location now, as the endpoint of several new pipelines that are being built to bring shale gas products to the coast for export. Mariner East 1 is an existing pipeline, which carries about 75,000 barrels per day of natural gas liquids and 2 new 350 mile pipelines, Mariner East 2 and  Mariner East 3 are nearing completion, bringing the total volume of NGL’s flowing to the coast up to approximately 600,00 barrels per day. A large portion of this is natural gas and LPG, but around 20% of the total will be  ethane, a large percentage of which is available for export. Target completion for these pipelines was near the end of 2017, but they have suffered many setbacks in the interim period.

Exports to international markets has started to come online now. We have lifted the first Ethane cargo out of Marcus, however permitting problems continue to impact the project quite significantly, so exports have temporarily stopped again.

The sister ships of Aurora are all designed for LNG burning, but using LNG as a fuel regularly not possible on a regular basis, simply because it was not available in small parcels in the market. Finding LNG as a bunker fuel was extremely difficult.

Navigator Aurora

Navigator Aurora also has two auxiliary engines which are also LNG powered. Navigator Aurora had initially operated on LNG, but as the vessel moved from the far east into the Middle East and towards Europe, it became almost impossible to find LNG bunkering parcels around a thousand tons or less, but we eventually found an LNG parcel in Sweden. The main purpose of loading LNG at that point, as we had not been able to source LNG as a fuel, the system had been dormant for almost a year by that point. So, we were not sure what the condition of the system was, even though it had been charged with nitrogen.

Reasons to convert

The Navigator Aurora is under a ten-year charter. So without the input and support of the charterers, who are actually saving the money on the fuel conversion, without their financial support, it would have not made any commercial sense for Navigator to do the project alone, but the reasons for the project are very compelling:

  • Compliance with 2020 Sulphur regulations;
  • Environmental stewardship;
  • Fixed fuel source & price;
  • Less bunkering days;

Navigator Gas will not be fitting scrubbers, but not because of strong objections to scrubbers as a means of  meeting 2020 compliance requirements. It is very much in terms of what our competition is doing, our leading position in the handy size LPG market and the age of our fleet. A majority of our ships are quite new and have very low  fuel consumption.

The outcome of the conversion to Ethane fuel Sulphur emissions was well-known beforehand and the reduction in NOx, SOx, and CO2 emissions is also very impressive,  but the target was to reduce SOx emmisions down to levels where it will be compliant with the 2020 regulations. There is a small drop in CO2 emissions as well, but not enough to meet 2030 or 2050 regulations.

Obtaining approval to use Ethane as fuel

It was quite a complex route to get ethane authorized as an alternative fuel to LNG. The first HAZID that was done with ABS back in 2014 was for a different kind of ship. This had to be revised significantly in 2017 to ensure that compliance with class flag and statutory requirements was still relevant. And more importantly to check against the updated  IGC Code, MARPOL Annex 9, Regulation 13. The HAZID review in 2017 identified that there were no new risks; the original 21 medium risks that were mitigated were still there, except for two concerning gas detection and ventilation.

The USCG was also notified to make sure we did not fall foul of any misinterpretations of IGC Code or classification or any State requirements while using ethane and not LNG as a fuel in US waters.

Testing of the new ethane mode involved using two cylinder test engine in Kawasaki in Japan, identically set up to the engine on Navigator Aurora. The main issue identified early on was the lower injection pressure on the engine leading to soot formation in the exhaust. Increasing the injection pressure from 300 to 400 bar was the solution, however it would have been extremely complex and very expensive to convert the fuel gas system to be able to inject fuel at 400 bar.

The far more cost effective solution was using the existing 300 bar system, without modifying the fuel gas system extensively and modifying the engine timing and fuel gas control system to reduce the soot emissions to acceptable levels. One of the most noticeable outcomes of the project was that we did not have to rewrite the NOx technical file, which would have been a major hurdle. The conversion was not considered to be a major conversion or substantial modification of the engine for the purposes of the NOx technical file and that was confirmed by ABS.

The list of components that had to be changed was quite extensive:

  • Cylinder Heads: To Reduce gas bore size through cylinder heads.
  • Chain Piping: Potential cracking due to lower temp if inner walled pipe failed.
  • Gas Inj Valves: Reduce gas pocket volume around valve body & new nozzle design.
  • Window Valves: Increased gas accumulator volume by changing end covers.
  • Gas Pr Sensor: To allow for higher amplitude pressure pulses.
  • Seal kits: Upgraded material to withstand the low temperatures.

Looking at some of the modifications, you will notice that some are for technical reasons, but the most significant, such as changing the cylinder heads, were to address safety concerns that had been identified during the HAZID.

The conversion work ran for 15 days and was completed roughly on schedule. Sea trials lasted for longer than expected, due to significant number of difficulties getting the engine to run on 100% gas burning, to allow fine tuning of the gas fuel and engine control system.

The main part of the project was a complete strip down of the engine. Change all the cylinder heads, gas valves and the liners and replace all of the gas chain pipes. The only outstanding items from that HAZID were ventilation and gas detection system. Ethane is heavier than LNG, so live smoke tests were done in the engine room to test dispersion patterns and identify where ventilation and gas detector modifications had to be made.

This project remains big news, it was an industry-first conversion of  an LNG-I engine to an ethane burning GI-E engine. Today Navigator Aurora is running regularly on ethane fuel and we are now working on converting the 20 DF auxiliary engines from LNG to ethane fuel as well.

Needless to say I was very proud to receive the GREEN4SEA Tanker Operator Award. Navigator Gas has now gained industry wide recognition for the progressive work we have undertaken to meet our collective environmental protection obligations and that recognition is very welcome.

Navigator Gas ambitions don’t end there. They are now involved in a JV project to develop ammonia as a fuel, to meet GHG reduction targets and the use of zero carbon fuels coming into force in 2050.


Above text is taken from Mr. Paul Flaherty’s presentation during the 2019 GREEN4SEA Conference.

View may view his presentation herebelow

The views presented hereabove are only those of the author and not necessarily those of  SAFETY4SEA and are for information sharing and discussion  purposes only.

Paul Flaherty joined Navigator Gas as Director of Fleet and Technical Operations in December 2014. Prior to this he was employed by JP Morgan Global Maritime as VP, Asset Management. Previously, he spent 17 years with BP Shipping Ltd as a Fleet and Technical Manager for both Oil and Gas vessels. Paul is a Chartered Engineer and a Fellow of the Institute of Marine Engineers & Science Technicians (IMarEST).