Marine Steam Turbines

Early Development

Steam turbines revolutionized ship propulsion with their introduction in the late 19th century, offering advantages over traditional reciprocating engines such as smaller size, reduced maintenance, and lower vibration. Despite the need for precise reduction gears or turbo-electric transmission to match the high RPM of turbines to the effective propeller speeds, the benefits included lighter weight and more compact engine rooms.

The journey of steam turbine propulsion began with the Turbinia in 1894, showcasing direct drive but facing challenges in aligning the turbine’s efficient speed with the propeller’s. Innovations like cross-compounding and the introduction of high-pressure (HP), intermediate pressure (IP), and low-pressure (LP) turbines in series enhanced efficiency and power. RMS Queen Mary (1934) exemplified advanced applications with multiple turbines driving each shaft through reduction gearboxes.

Shift from Marine Steam Turbines to Diesel Engines

The shift from marine steam turbines to marine diesel engines as the dominant mode of propulsion in commercial shipping over the last century was influenced by several key factors. These factors reflect the maritime industry’s ongoing pursuit of efficiency, reliability, and cost-effectiveness, alongside evolving regulatory and environmental standards. The main reasons for this shift include:

1. Fuel Efficiency: Marine diesel engines are generally more fuel-efficient than steam turbines, especially at part load and varying power demands. This efficiency translates into lower fuel consumption for the same distance traveled or load transported, which is a critical factor given that fuel costs represent a significant portion of a vessel’s operational expenses.
2. Operational Flexibility: Diesel engines can start and stop more quickly than steam turbine systems, which require time to raise steam. This operational flexibility is particularly advantageous for vessels that need to navigate through ports and congested waterways, where frequent adjustments to the engine’s power output are necessary.
3. Lower Operational Costs: Beyond fuel efficiency, diesel engines tend to have lower operational costs in terms of crew requirements and maintenance. Steam turbine systems, especially those that are not integrated with gas turbines in combined cycle configurations, typically require more specialized knowledge for operation and maintenance, translating into higher staffing costs.
4. Simpler Fuel Handling and Storage: Diesel fuel requires less complex handling and storage systems compared to the heavy fuel oil (HFO) and bunker fuel used in steam turbines. This simplicity can reduce the costs and logistical challenges associated with fuel management onboard.
5. Advancements in Diesel Engine Technology: The development of high-efficiency, high-reliability diesel engines, including both medium-speed and low-speed versions, has made diesel propulsion increasingly attractive. Innovations in engine design, materials science, and fuel injection technologies have continually improved the performance and reduced the environmental impact of diesel engines.
6. Environmental Regulations: The global push towards reducing emissions from ships has favored the adoption of marine diesel engines, which can be more easily adapted to meet stringent emissions standards. Technologies like selective catalytic reduction (SCR) and exhaust gas recirculation (EGR) have been more readily applied to diesel engines to reduce nitrogen oxides (NOx), sulfur oxides (SOx), and particulate matter emissions.
7. Flexibility in Fuel Types: The development of diesel engines capable of running on a variety of fuels, including marine gas oil (MGO), low-sulfur fuels, and, more recently, liquefied natural gas (LNG), has provided additional flexibility in responding to changes in fuel availability and price, as well as environmental regulations.

While marine steam turbines continue to be used in certain applications where their specific advantages are pronounced (such as LNG carriers using boil-off gas), the overall trend has favored diesel engines for the majority of commercial shipping needs. The industry’s focus on operational efficiency, cost reduction, and environmental compliance has driven this shift and continues to influence the development of marine propulsion technologies.

Introduction to Marine Steam Turbines

Marine steam turbines are engines that convert thermal energy from steam into mechanical work to propel ships. This technology has evolved significantly since its introduction in the late 19th century, offering efficiency and reliability for maritime transportation. Steam turbines work by expanding steam through a series of blades mounted on a shaft, which turns a propeller to move the ship. They are particularly favoured for their smooth operation, high power output, and efficiency at high speeds, making them suitable for large vessels like LNG carriers and naval ships. For more in-depth information, I recommend consulting specialized resources or the provided website links for specific details on designs, operations, and applications of marine steam turbines.

Marine steam turbines serve as a propulsion mechanism for ships, translating thermal energy from steam into mechanical energy to drive the ship’s propellers. This technology has been pivotal in the evolution of marine propulsion, offering significant advantages in terms of efficiency, especially for long voyages. While the use of marine steam turbines has seen fluctuations over the years, especially with the rise of diesel and gas turbine engines, they remain integral in specific segments of the maritime industry.

Several types of ships continue to use marine steam turbines, including:

• LNG Carriers: Many liquefied natural gas (LNG) carriers use steam turbines powered by boilers heated by the gas that evaporates from the cargo. This design capitalizes on the availability of “boil-off” gas as a fuel, making steam turbines a preferred choice for some operators.
• Certain Tankers: Similar to LNG carriers, some tankers designed for transporting liquefied petroleum gas (LPG) or certain chemicals might use steam turbines.
• Naval Ships: Many navies around the world prefer steam turbines for their ships, including aircraft carriers, certain destroyers, and cruisers, due to their high power output, reliability, and the ability to use nuclear power as a heat source for the boilers.
• Some Cruise Ships and Icebreakers: A limited number of specialized ships, such as icebreakers and some cruise ships, might use steam turbines for propulsion due to their specific operational requirements.

Main Producers of Marine Steam Turbines

Marine steam turbines, which are critical components for the propulsion of various types of ships, including naval vessels, cargo ships, and some types of passenger ships, are produced by a number of companies around the world. The market for marine steam turbines is relatively specialized, with a few key players dominating the scene. As of my last update, the main producers globally include:

1. General Electric (GE): GE is a major American multinational conglomerate that, among its wide range of products and services, offers marine propulsion systems, including steam turbines. GE’s marine steam turbines are known for their reliability and efficiency, and they have been used in a variety of naval and commercial ships.
2. Mitsubishi Heavy Industries (MHI): Based in Japan, MHI is a leading producer of a broad array of industrial and engineering products, including marine machinery and engines. MHI’s marine steam turbines are well-regarded for their performance and have been installed in various types of vessels worldwide.
3. MAN Energy Solutions: Headquartered in Germany, MAN Energy Solutions provides large-bore diesel engines and turbomachinery for marine and stationary applications. Their product line includes steam turbines that are used in marine propulsion systems.
4. Rolls-Royce (now part of BAE Systems): Rolls-Royce was a key player in the marine steam turbine market, offering a range of propulsion systems for naval and commercial use. After the acquisition of Rolls-Royce’s commercial marine business by Kongsberg Gruppen and the integration of its naval marine and nuclear submarines division into BAE Systems, the legacy of Rolls-Royce’s marine propulsion technology continues under these brands.
5. Siemens: A German conglomerate, Siemens offers a wide range of electrical engineering and electronics-related products and services, including marine solutions. Siemens’ marine steam turbines are known for their efficiency and are used in various ships for propulsion and onboard power generation.
6. Kawasaki Heavy Industries (KHI): KHI is a Japanese multinational corporation with a diverse product lineup that includes aerospace equipment, rolling stock, ships, and power plants. Kawasaki’s marine steam turbines are used in a variety of vessels, highlighting the company’s strong presence in the marine industry.

These companies are known for their technological innovation, global reach, and extensive experience in the marine industry. They continue to develop and refine marine steam turbines to meet evolving demands for efficiency, reliability, and environmental compliance in the maritime sector.

Continued Applications of Marine Steam Turbines in Modern Shipping

Marine steam turbines, with their roots in early 20th-century naval engineering, have played a pivotal role in the evolution of ship propulsion. The introduction of cruising turbines around 1911, aimed at enhancing fuel efficiency during reduced-speed operations, marked a significant technological leap. This period also saw the advent of reduction gears, allowing for the efficient high-speed operation of turbines and heralding the transition from reciprocating engines to fully geared turbine systems, especially in naval vessels. Such advancements, along with continuous improvements in steam pressure and temperature, set a new benchmark for propulsion in warships, emphasizing speed and efficiency.

Despite the widespread transition to gas turbines and diesel engines in the 1980s, marine steam turbines have maintained a niche yet critical presence in today’s maritime industry. They are particularly prevalent in nuclear-powered naval ships, LNG carriers, and some auxiliary vessels, where the unique attributes of steam turbines—such as their efficiency and the strategic advantage offered by nuclear propulsion in submarines and icebreakers—play a crucial role.

Operating on the principle of converting steam’s thermal energy into mechanical energy, marine steam turbines facilitate ship propulsion through the expansion and cooling of steam. This process begins with boiling water in a boiler to generate steam, which is then propelled at high pressure through a turbine. Equipped with a series of blades mounted on a shaft, the turbine harnesses the steam’s energy as it expands and cools, thereby rotating the shaft. This mechanical rotation is subsequently transmitted to the ship’s propellers, either through a gearbox in geared turbine systems or directly in direct drive turbines, to propel the vessel forward.

Despite shifts in technological preferences and the advent of more modern propulsion methods, the specific advantages of marine steam turbines continue to underscore their importance in certain segments of the maritime sector, highlighting their enduring legacy and ongoing utility in commercial and naval applications.

Beyond Propulsion: Power Generation at Sea

Marine steam turbines have expanded their role to include onboard electricity generation, addressing the need for continuous power for essential shipboard systems like lighting, navigation, and communication. Mitsubishi Heavy Industries’ ultra-steam turbines represent the pinnacle of this technology, offering unmatched efficiency and reliability for LNG carriers and container ships. Their optimal performance at steady speeds renders them ideal for lengthy maritime voyages. Auxiliary steam turbines are crucial for maintaining a ship’s operational capabilities, providing a stable supply of electrical power. Their significance is further highlighted by Marine Insight’s overview of ship’s turbine generators, emphasizing their contribution to the smooth functioning of onboard systems.

Turbo-electric drive emerged as an innovative solution, combining steam turbine generators with electric motors for propulsion, offering initial cost savings and enhanced manoeuvrability. Turbine generators stand as a beacon of clean energy generation aboard ships, leveraging steam—a fuel that is abundant, eco-friendly, and cost-effective. This system derives its steam from the vessel’s own boiler plant, eliminating the need for conventional fuels like heavy or diesel oil. In a turbine generator, high-pressure steam propels a turbine, converting the steam’s thermal energy into rotary motion. This turbine is directly connected to the alternator’s rotor, transforming the rotational energy into electrical power efficiently. The electricity produced is then routed to the ship’s main switchboard, powering various onboard systems.

Beyond generating power, steam turbines serve a pivotal role in ship propulsion. They can directly drive the ship’s propeller shafts, necessitating reduction gears to lower the turbine’s high RPM to a suitable level for the propellers. Additionally, steam turbines can power slow-speed motors linked to the propeller shafts, offering a streamlined method to propel the vessel.

Key Components of the Turbine Generator System:

• Turbine Prime Mover: Acts as the main driver in the turbo-generator setup, sharing a shaft with the alternator’s rotor to ensure seamless power conversion.
• Alternator: Transforms the turbine’s rotational movement into electrical energy, supplying power to the ship’s main electrical grid.
• Steam Control Governor: Regulates the turbine generator’s speed during start-up, normal operation, and shutdown phases by controlling steam flow.
• Steam Control Valve: Installed within the steam line, these valves adjust the steam’s flow from the boiler, managed by the governor for optimal operation.
• Condensate Pump: Recirculates condensed steam back to the boiler for reheating and reuse, enhancing the system’s efficiency.
• Vacuum Pump for Glands: Maintains the turbine casing’s vacuum by injecting steam into the shaft’s glands, preventing pressure drops.
• Condenser: Acts as a heat exchanger, cooling and condensing the turbine’s exhaust steam back into water, ready to be reheated.
• Vacuum Pump Header Tank: Cools the vacuum pump, handling the high-temperature steam effectively to ensure system longevity.

Turbine generators exemplify clean, efficient power generation on ships, utilizing steam to not only generate electricity but also propel the vessel. Through innovative engineering, these systems maximize the potential of steam, offering a sustainable alternative to traditional fuel-based power.

Besides propulsion, steam turbines also find applications in onboard power generation. Auxiliary steam turbines ensure a continuous supply of electrical power for lighting, navigation, communication systems, and other essential operations onboard. An introduction to ship’s turbine generators by Marine Insight highlights the critical role of these systems in maintaining the operational capabilities of modern ships.

Operational Advantages and Suitability

Marine steam turbines are prized for their operational efficiency, reliability, and ability to facilitate quiet and smooth operations. These attributes make them exceptionally suitable for large vessels that embark on extended voyages, such as container ships, oil tankers, and passenger liners. The introduction of ultra-steam turbines by Mitsubishi Heavy Industries has marked significant advancements, offering enhanced efficiency and reliability for the modern maritime industry, particularly for LNG carriers and container ships.

Environmental Considerations and Innovations

Despite their advantages, the environmental impact of marine steam turbines, particularly concerning fossil fuel consumption and greenhouse gas emissions, poses challenges. The maritime industry is under increasing pressure to adopt more sustainable practices. The commercial future of marine steam turbines depends on their adaptation to environmental regulations and fuel efficiency standards. Riviera Maritime Media discusses the potential for marine steam turbines in a market that increasingly values sustainability, pointing out that innovations in turbine efficiency and fuel flexibility could secure their relevance (Riviera Maritime Media).

In response, companies like MAN Energy Solutions are developing steam turbines that offer enhanced efficiency and are compatible with a broader range of fuels, including low-emission biofuels and synthetic fuels. These developments aim to reduce the environmental footprint of maritime operations while ensuring the viability of steam turbine technology in the future.

Future Directions

The future of marine steam turbines lies in their ability to adapt to the evolving demands of the maritime industry. This includes not only improvements in efficiency and reductions in emissions but also the integration with emerging technologies such as digitalization for enhanced operational monitoring and predictive maintenance. As the industry moves towards more sustainable and efficient propulsion systems, marine steam turbines must evolve to meet these challenges.

Despite their advantages, marine steam turbines face environmental sustainability challenges, particularly with the global push towards reducing greenhouse gas emissions. The shipping industry’s need for more sustainable practices raises questions about the future of steam turbines. Riviera Maritime Media discusses these challenges, suggesting that innovations in efficiency could secure a place for steam turbines in future marine propulsion systems (https://www.rivieramm.com/opinion/opinion/is-there-still-a-commercial-future-for-marine-steam-turbines-33696).

In response, manufacturers like MAN Energy Solutions are developing steam turbines with enhanced efficiency and fuel flexibility, including compatibility with biofuels and synthetic fuels (https://www.man-es.com/process-industry/products/steam-turbines). This adaptability could be crucial for maintaining the relevance of steam turbines in environmentally conscious shipping operations.

Conclusion

Marine steam turbines have played a pivotal role in the development of modern shipping, offering efficiency, reliability, and high performance. While facing environmental challenges, ongoing innovations and adaptations suggest a continuing role for steam turbines in maritime propulsion. Manufacturers and engineers are focused on enhancing efficiency and environmental compatibility, ensuring that steam turbines can meet the demands of the future shipping industry. With their ability to adapt and evolve, marine steam turbines are poised to remain a significant technology in the maritime world.