CMMI Monthly Meet Deliberates on New LNG Vessel Design and Containment

Padmesh Prabhune

Photos from Jaggu

The Company of Master Mariners of India (CMMI), a professional body representing Master Mariners with the purpose of developing and promoting the traditions and standards of the Merchant Navy in India in its monthly lecture meeting held on Thursday, 20th April at MOL Maritiime India Pvt Ltd (MOLMI), organized a lecture by Capt Tapan Kumar Panda, Extra Master, Manager Training, MOL Maritime India Pvt Ltd (MOLMI). He was joined by Mr Satish Kumar Singh, MD, MOLMI as well.

While Capt Panda elaborated on New LNG Vessel Design and Containment, Mr Singh explained about the Propulsion System. The hybrid lecture was appreciated across the audiences.

Capt Panda elaborated on LNG Containment System Mark III and NO 96, both cryogenic liners used to contain liquefied gas at low temperatures during shipping, onshore and offshore storage, at atmospheric pressure.

Since 2008, GTT has introduced Mark III design evolutions to improve the thermal and structural efficiency of the technology. Its latest development, Mark III Flex+, offers a guaranteed boil-off rate of 0.07% V/day, thanks to an insulation thickness increased of 480 mm.

NO96 Technology

In this the primary and secondary membranes are made of Invar®, a 36% nickel-steel alloy, 0.7mm thick. The primary membrane contains the LNG cargo, while the secondary membrane, identical to the primary, ensures a 100% redundancy in case of leakage. Each of the 500mm wide Invar® strakes is continuously spread along the tank walls and is evenly supported by the primary and the secondary insulation layers.

The perlite has been replaced by foam in NO96 L03 or by glass-wool in NO96 GW evolution. A set of reinforced boxes have also been developed in order to meet requirements for systems sustaining higher loads.

Presentation on LNG Propulsion – By Mr Singh

After the lecture by Capt Panda on vessel membrane system Mr Singh made a presentation on LNG propulsion. Elaborating further he said, “A marine LNG engine is a dual fuel engine that uses natural gas and bunker fuel to convert chemical energy in to mechanical energy. Due to natural gas’ cleaner burning properties, the use of natural gas in merchant ship propulsion plants is becoming an option for companies in order to comply with IMO and MARPOL environmental regulations. The natural gas is stored in liquid state (LNG) and the boil-off gas is routed to and burned in dual fuel engines.”

Speaking about the propulsion Mr Singh mentioned that the set-up of the propulsion system depends on the vessel size, trade, or type of operation Steam turbine has been the dominating propulsion plant used on LNG carriers since 1960. Because it offers dual fuel burning capability, low maintenance cost and high reliability.

Up to 2010, LNG carriers were generally constructed with steam turbines for propulsion. While these vessels still make up a large part of the fleet, they have a cost disadvantage to modern vessels due to higher fuel consumption. Starting around 2002, owners started building LNG carriers with dual fuel diesel engines or tri fuel diesel engines, making up the bulk of the current modern tonnage.

LNG today has lesser Boil off related loss of 0.08%. The dual-fuel two-stroke engine is based on the combustion principle of operating on Heavy Fuel Oil (HFO) or Marine Diesel Oil (MDO) together with high-pressure natural gas, where the fuel is injected and burned directly as opposed to the premixed or Otto-cycle combustion.

Owners currently have the choice of two different engine solutions for two-stroke, low speed propulsion for LNGC vessels: MEGI, by MAN Diesel and Turbo, and X-DF, by WinGD (previously Wärtsilä). MEGI vessels generate negligible methane slip during gas operation making it the most environmentally-friendly technology available. The reduction of greenhouse gas emissions, including methane slip, has been found to be 22% lower compared to fuel oil.

The X-DF Technology: Low Pressure Gas Injection

Mr Singh mentioned that in view of the increasing demand for low-speed, dual-fuel engines, WinGD developed the lean burn Otto combustion process with low-pressure gas admission and micro-pilot ignition for its two-stroke engine portfolio. The first LNG X-DF vessel was delivered in 2017. The low-pressure dual-fuel technology, known as the X engine series, is a further development. In contrast to high-pressure gas injection engines, which operate on the Diesel cycle, X-DF engines work on the Otto cycle when operated in gas mode.

The particulate matter emissions on X-DF engines is reduced to almost zero, and the CO2 emissions, inherent to burning natural gas, are further reduced. The total hydrocarbon content of X-DF is considerably lower, compared to four-stroke low-pressure DF engines.

Acknowledging the in depth lectures by both speakers, Capt JS Kanwar presented the bouquet to speakers Capt Panda and Mr Singh as a goodwill gesture. To conclude the meeting Capt Sasikumar delivered the vote of thanks appreciating all concerned.

Marex Media