Do the engines run on conventional fuel only?
The main engine will become a dual-fuel engine and is able to burn compliant fuel in the conventional way. The engine can also use Propane or Butane or a mix of the two as the main fuel source, with a small amount of compliant pilot fuel. Flexibility is therefore retained by using LPG or compliant fuels to take advantage of optimal fuel market prices.
What is the gas consumption?
At 16 knots, the main engines will consume approximately 35.6mt LPG per day and 1.8mt pilot fuel per day with cargo onboard. In addition, the auxiliary engines will consume approximately 4.9mt marine diesel oil (MDO) or compliant fuel per day. At 14 knots ballast, the engines will consume approximately 19.7mt LPG per day and 2.2mt pilot fuel.
Is the cargo used as fuel for the main engine?
The cargo is not necessarily used as fuel, but cargo can be transferred to the LPG fuel deck tanks for it to be used as fuel. Cargo can be transferred to the fuel gas supply system for the main engine by pumping from the cargo tank to the deck tank.
Is the fuel gas system connected to the cargo system?
Yes, the fuel gas system is part of the cargo system. The deck tanks can be run completely isolated from the cargo tanks or as part of the cargo system.
At what pressure is the LPG fuel delivered to the engine?
The propane or butane is pumped at a pressure of 50 barg to the engine room. The LPG is then further pressurised for the injection to the engine, which is the same process as for conventional fuel.
Does LPG in the deck tanks need conditioning?
Under all normal scenarios, conditioning is not required. The deck tanks applied are semi-refrigerated, but the pressure build is much slower than the rate of consumption with LPG being used as fuel for the main engine. In case the deck tanks are not emptied for consumption, they are connected to the cargo reliquefaction system and can be conditioned independently of the cargo tanks.
Are the deck tanks able to load fully refrigerated cargo?
Yes, the deck tanks can load fully cooled cargo.
Will there be segregation of different cargo grades?
Yes, there is segregation of cargo grades so different fuel can be in the cargo tanks and deck tanks. Both deck tanks will contain the same grade of fuel.
How is the gas consumption measured and monitored?
Both compliant fuel and LPG in the engine is measured using mass flow meters.
Can the engine run on gas during maneuvering?
No, the engine will automatically change over to conventional compliant fuel when the main engine load is below 10%. While the vessel is maneuvering in port, or at any time the engine load is below 10%, the gas burning option cannot be selected.
Is there any possibility of contaminating cargo tanks with the return fuel?
No, any fuel that is returned from the fuel gas system will not be returned to the cargo system. All the LPG flows from the deck tanks into the fuel gas system which then supplies the engine. The engine cannot supply fuel gas directly from the cargo tanks. Once pumped from the deck tanks, it will be contained within the closed loop system fuel gas system. This includes a small tank called a catch tank. Any fuel gas returned will be stored in the catch tank.
How much pilot fuel is used?
Pilot oil consumption will be 5% of the gas consumption, down to a load of approximately 75%. At lower loads, the pilot oil will increase gradually to about 15% of the gas consumption at an engine load of 25%. Fully loaded with cargo at 16 knots, pilot fuel consumption is approximately 1.8mt per day and at 14 knots, it is approximately 2.2mt per day
What happens if there is a gas leak in the engine room?
In the event of a gas leak, the gas master valves will close and the double wall piping to the engine room and the main engine will be purged with nitrogen.
What kind of cylinder lubrication oil (CLO) will the engine use?
The engine will use the same cylinder lubricating oil (CLO) as currently in use for 2020 compliant fuel. The cylinder lubrication will need to be adjusted accordingly to the cylinder condition, which is also currently the case with vessels burning 2020 compliant fuel and LNG burning engines.