MAN’s ME-GIE re-writes the rulebook when it comes to two-stroke propulsion
The GasChem Orca - a 28,580-tonne, 188 m chemical carrier - started sailing nearly a year ago between Houston and Teeside, bearing a load of semi-refrigerated ethylene and ethane. Technically a liquefied ethylene gas (LEG) carrier, the Orca is an original vessel in several ways, but its engine is particularly so. Known as ME-GIE (for gas-injection ethane), it is a world first that sets new parameters in two-stroke propulsion.
Designed and manufactured by Mitsui and MAN, it is the first gas-injection two-stroke that can run on ethane. Several years in development, the ME-GIE is an important advance on the gas-injection engine (ME-GI) concept that has sold in the hundreds of units. And intriguingly, it can run on just about anything.
As MAN Diesel & Turbo sales manager Rene Sejer Laursen said at the launch of the GasChem Orca: “This development is particularly exciting as it opens up the prospect for multi-fuel combustion, including the combustion of methane, waste gas and volatile organic compounds.”
In practical terms, that means the vessel can run on a mixture of LPG and methane or ethane; from an environmental viewpoint, the latter is a particularly attractive fuel for shipowners because its emissions profile is similar to methane, while containing negligible sulphur and comparatively lower Co2.
So the power unit’s ability to burn waste gases is of considerable interest for a maritime industry looking for cheaper forms of fuel. Waste gases can include anything from light hydrocarbons to volatile organic compounds (VOCs) that are given off crude oil when it is stored or being loaded. If VOCs can be captured and put to good use instead of being lost, that is clearly a positive from every standpoint.
As MAN pointed out, a VOC-burning engine suggests numerous long-term possibilities. “It opens the door for new applications for the engine in, for example, shuttle tankers or off-shore applications such as floating production storage and offloading vessels where VOCs are abundant,” explained Mr. Laursen.
There are now two of these vessels sailing between Teeside and Houston; the Orca joined a sister ship, the GasChem Beluga - launched in late 2016 - and their performance has attracted considerable interest.
Owned by Norway’s Ocean Yield, which specialises in long-term charters, the LEG carriers have been handed over on a 15-year bareboat charter to Germany’s Hartmann Group, which in turn sub-chartered them to Middle East group Sabic Petrochemicals.
The vessels have now been in action for a combined two and a half years. Although the Orca and Beluga are not designed to tear up the oceans, the engines can push them at an average speed of 14.5 knots and a maximum speed of 21.2 knots, fast enough for a LEG carrier.
MAN did not provide sales figures, but the signs are that the ME-GIE has a promising future. Barely had the engine been released that the manufacturer received orders for eight units.
MAN's ethane-burning engine is a prime example of the efforts enginebuilders and suppliers are putting into two-strokes. Earlier this year, Switzerland-based Winterthur Gas & Diesel, a specialist in two-stroke technology, unveiled an advanced diagnostics system that it has been developing with Greek ship-performance specialist, Propulsion Analytics.
Designed for two-stroke diesel and dual-fuel engines, the system is known as Wide and delivers real-time data to the crew that, Winterthur said, “will provide live trouble-shooting and diagnostic advice”. As Winterthur Gas & Diesel vice-president for operations Andrew Stump explained, the system will “optimise engine performance in all its aspects, [such as] fuel consumption, power and emissions”.
Not only will the crew see the data, so will the office back on terra firma. Mr. Stump added: “[The diagnostic system] will be able to predict malfunctions ….in order to prevent failure as well as fix technical problems faster and more economically.”
According to Winterthur, a prototype has been running since 2017 and this year the system will be progressively installed on Winterthur’s entire portfolio of two-strokes. Winterthur told Marine Propulsion that it already has orders to retrofit Wide on 55 ships during 2018.
As Wärtsilä said in a statement in March this year, "pistons are the foot soldiers of most energy generation systems…and the wear and tear on them is excessive, pressures are huge, and tolerances are tight.” A piston can be 1 m in diameter and weigh up to 1,400 kg; a massive rotating mass that is inevitably prone to breakdown.
In another example of the constant refinement of marine engines, Wärtsilä has unveiled a means of doubling the functioning life of pistons on two-stroke engines. After being tested on container vessels for up to 15,000 running hours, Wärtsilä and QuantiServ - its global maintenance and repair subsidiary - have developed a new coating and reconditioning system that can double the working hours of their piston heads. Known as QS 50K, the system can add a minimum 50,000 hours in running time, compared with 24,000 hours in the case of standard chromium-6 plating.
The laser-controlled process can be done in a day according to the company: “This means less downtime and huge cost savings for customers,” said QuantiServ manager for workshop standards and tool development Peter Blok. In fact, tests show that a QS 50K-coated piston can outlive a brand new one, according to Wärtsilä. As a bonus, the system can also be applied to non-Wärtsilä piston heads.
Returning to the LEG carriers, their innovations do not start and end with the engines. Both vessels feature space-saving Star-Trilobe tanks – three cylinders combined into one – that give an extra 30% of space compared with standard bi-lobe tanks. As a result, the vessels boast a cargo volume of nearly 38,000 m3, making them the world’s largest LEG carriers.
The family-owned Hartmann group, a specialist in gas tankers, also developed a new kind of low-resistance hull shape for these vessels that makes their engines more effective. The superstructure is located at the bow and the engine at the stern, which Hartmann says makes for a highly efficient distribution of weight and achieves a significant reduction in ballast water. Hartmann also designed a wave-piercing entry, dubbed the “svelte bow”.
Encouraged by the reaction to the ME-GIE power units, MAN is pushing on with two-stroke development. In March, it announced the building of a new test-engine facility in South Korea in collaboration with the engine and machinery division of Hyundai Heavy Industries, with the purpose of advancing dual-fuel propulsion.
According to Lars Juliussen, head of MAN’s diesel and turbo research centre in Copenhagen, the facility will focus on “environmentally friendly, cost-competitive gas engines and related equipment”.
The centre will start up in early 2019 and MAN is particularly interested in developing pump vapourisers, a new technology that pressurises and vapourises LNG fuel to the exact pressure and temperature required by gas-injection engines. Launched recently by MAN’s Copenhagen base, the pump vapouriser also makes fuel-gas supply system installations more compact, which reduces cost and weight.
With so much action and interest in the sector, the gas-injection engine is rapidly becoming one of the success stories of marine propulsion.