Innovate under pressure

Most of the new LNG-powered vessels will be built with two-stroke cycle engines. In fact, more than 80% of all LNG ships ordered in 2023 had two-stroke engines, according to data from Clarksons. A primary reason is that two-stroke engines significantly reduce methane slips and are generally considered more fuel-efficient than four-stroke engines, which makes them a preferred option for many shipping companies, especially for larger vessels.

Because of its operating principles, a two-stroke engine needs a higher fuel injection pressure (300 bar). Therefore, the fuel gas supply system (FGSS) design for a two-stroke engine is more complex than for a four-stroke engine, as it represents the integration of mechanical, thermal, and electronic components designed to handle LNG safely and efficiently. Thus, the system requires components that can handle the increased pressure, contributing to better fuel atomization and combustion, all within the constraints of a compact and continuous operating cycle.

The cold end: Ensuring an efficient transfer of LNG to the engine

The objective of the FGSS is to deliver fuel to the engine at the required temperature and pressure. In the case of LNG, the fuel is pumped in its liquid form (at -162°C/-260°F) from the storage tank and vaporised to a gaseous state before being injected into the engine.

In a high-pressure FGSS for LNG, the cold end is critical in maintaining the natural gas in a liquid state during pumping, ensuring it does not vaporise prematurely. This is essential for maintaining an efficient and safe transfer to the engine under high pressure. Cold ends directly impact the fuel system’s overall performance, influencing fuel delivery rates, energy efficiency, and emission levels.

As the cold end is the component that comes into direct contact with the cryogenic fluid, the design, construction, and material selection are crucial for the successful operation. High-pressure LNG pumps are typically built with three cold ends, which is considered the optimum design regarding flow, efficiency, and reliability in operation.

A new high-pressure pump-design for longer service intervals

High-pressure LNG fuel systems are still relatively new to the maritime industry, and a common issue is the wear and tear on critical components. This is driving efforts to improve LNG pump technology to enhance reliability and operational efficiency.

Svanehøj has addressed the need for more durable and maintenance-friendly components by developing a complete high-pressure pump solution exclusively designed for marine LNG fuel systems, and a separate cold-end component for LNG retrofit projects.

The ‘Svanehøj HPP Triplex Unit’ is a reciprocating (piston) pump capable of achieving and maintaining very high pressures under cryogenic conditions. The pump delivers a pressure of 315 bar and a flow rate of 4.3 m3/h. The compact unit is designed with a belt drive system, installed on a skid for easy transportation and installation.

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