Proposal to Improve Historical Accuracy of Boiler Techs

[BattleshipOfDestruction]

This topic is to discuss an improvement to the generic and immersion breaking boiler types in the game. More topics will be coming about other modules and discussions on their accuracy and possible improvements that can be made.

There are a lot of nonsensical boiler types here in the Vanilla Options. This time the devs decided to be very vague and generic with the options while focusing on the drafting systems installed in the boilers, not the type of boiler (fire-tube or water tube), presence of economizers and superheaters and the overall design of the boiler itself in addition to the aforementioned drafting systems. As such all of the boilers in game are so generic, I had to do research essentially from scratch which took me multiple months to compile. The prose of the descriptions in my barebones version of the improvements had to be refined over the last few weeks to make sure it was well explained about the intricacies of boiler construction, new technology and their overall evolution throughout the time period. Hopefully what I have compiled provides a thoroughly detailed evolution on the four most essential highlights (as there were only four boiler slots in game) of boiler evolution from 1890 to 1945.

At Tier I we have Scotch Fire-Tube Marine Boilers. Introduced in 1890 and obsolete by 1900 (In game), Scotch Fire-Tube Boilers were a mainstay of the late 19th and early 20th centuries. They were normally stoked with coal by hand, but some were converted to use mechanical feeders of solid or crushed coal, crushed coal with oil spraying devices, or pure fuel oil. This design was most efficient when used with multiple expansion piston steam engines; however, it was generally inadequate for steam turbine engines due to the boiler's low pressure. As an early design, it was also the heaviest type of boiler. Scotch boilers featured a cylindrical shell with one or more large fire-tubes running through it. Water surrounded these tubes, and the combustion gases passed through the tubes, heating the water and generating steam. This design was simple and robust, making it easy to construct and maintain. Scotch boilers had several variants, including the double-ended Scotch boiler, which featured fire-tubes and furnaces at both ends of the cylindrical shell, increasing the steam-generating capacity. Despite their eventual obsolescence, Scotch boilers played a crucial role in the development of marine engineering, providing reliable steam power for many early steamships. By 1900, these boilers became less common in new installations beyond merchant craft and land applications as the new water-tube boiler took its place. Water-tube boilers offered superior efficiency due to their more effective method of heat transfer and higher quality of construction, which allowed them to operate at much higher pressures than their fire-tube predecessors. Fire-tube boilers in existing warships were gradually phased out and replaced with their water-tube counterparts, a conversion process that was mostly complete by the 1930s.

Preliminary Values:
Funnel Capacity: 0%

Smoke Interference: 75%

Engine Cost Per Weight: -25%

Engine Vibrations: 25%

Boiler Weight: 50%

Maintenance Cost: 0%

Fuel Efficiency: 0%

Fuel Stowage: 0%

 

At tier II we have the Babcock and Wilcox Express Tube Marine Boilers. With the example represented here being introduced in 1900 and available until 1930 (in game). In the late 1890s, the Babcock and Wilcox Express Tube Boilers were introduced. They were fundamentally different from the later Yarrow and Admiralty Boilers as they evolved from the earlier French Belleville water-tube boilers. These boilers were dimensionally narrower in width and shorter in height but significantly longer in length compared to their fire-tube counterparts and the Yarrow Boiler. They featured a single drum with feedwater drawn from the bottom via pumps into a header that supplied the inclined water-tubes. The water-tubes then supplied steam back into the top of the drum. The boiler's furnaces were located below the tubes and drum. The "Express Tube" designation referred to its straight water tubes which connected the upper steam drum to the lower tubes heated directly by the furnace. This minimized the risk of overheating and tube burnout, ensuring a reliable steam supply. When introduced, it featured induced drafting, where the hot gases and combustion products from the boiler rose through the chimney and out the funnels, creating a vacuum that drew fresh air into the furnace through strategically placed air vents throughout the ship's upper decks. By 1900, to allow for the pressures needed to turn steam turbines, the boilers were equipped with one of the first superheater coils, which were located downstream of the furnace cavity, with steam flowing parallel to the flue gas. It also featured one of the first economizers, which preheated the feedwater using residual heat from the boiler's exhaust gases that would have otherwise been lost to the atmosphere. By doing so, it increased fuel efficiency by reducing the amount of fuel needed to heat the water to steam temperature and helped reduce thermal shock to the boiler’s metal components, extending the boiler’s lifespan and reducing maintenance requirements. Babcock and Wilcox boilers of various types were extensively used by the United States Navy and in some Royal Navy warships. However, their tube design was much more complex than earlier fire-tube boilers. Similar to their French Belleville predecessors, the design suffered from complex tube bends and angles, making cleaning and maintenance very difficult. If not properly cleaned and maintained, it could lead to blockages from scale buildup in the bends.

Preliminary Values:
Funnel Capacity: 25%

Smoke Interference: 25%

Engine Cost Per Weight: 0%

Engine Vibrations: 50%

Boiler Weight: 25%

Maintenance Cost: 25%

Fuel Efficiency: 10%

Fuel Stowage: -5%

 

At Tier III we have the Yarrow Water-Tube Marine Boilers. Originally introduced around the same time as the Babcock and Wilcox boiler, with the example represented here produced in 1910 (Obsolete by 1930 ingame), Yarrow Water-Tube Boilers were a type of space-efficient and thermally efficient boiler that were better to work with and maintain compared to the temperamental and hard-to-clean Thornycroft Boiler, Babcock and Wilcox Express Tube Boiler, and the earlier French Belleville Boiler. Dimensionally, the Yarrow and later Admiralty Boilers were shorter in length compared to the Babcock and Wilcox Express Tube Boiler, but were slightly wider than that design. This change was necessary as the straight tubes between its three drums (upper steam drum and two lower water drums) contributed to its ease of maintenance and efficient water circulation, preventing overheating and tube burnout. Developed by Alfred Yarrow, these boilers had a relatively simple and robust construction. They used a natural circulation system, where the heated water rose to the steam drum and cooler water descended back to the water drums. This natural flow eliminated the need for complex pumps and provided a reliable steam supply. The superheater coils were initially placed outside the main tube bank. Later designs became asymmetrical, with the tube bank on one side doubled and a hairpin-tube superheater placed between them. This variant was one of the first to introduce a forced drafting system. This is where fans supplied air to the furnace, ensuring complete combustion of the fuel at positive air pressure and ensured efficient induction of combustion gases. This system increased fuel efficiency at the cost of increased smoke generation. These boilers, like their Babcock and Wilcox predecessors, featured a more efficient economizer, further increasing fuel efficiency. These boilers saw widespread use in both commercial and naval vessels. Their reliability and efficiency made them a popular choice, contributing significantly to the advancement of marine engineering during the early 20th century.

Preliminary Values:
Funnel Capacity: 50%

Smoke Interference: 50%

Engine Cost Per Weight: 25%

Engine Vibrations: 25%

Boiler Weight: 0%

Maintenance Cost: 15%

Fuel Efficiency: 25%

Fuel Stowage: -10%

 

Finally at Tier IV we have the Admiralty Three-Drum Water-Tube Marine Boilers. It was introduced in the early 1930s and rendered obsolete by 1950 (ingame). An evolution of the Yarrow Water-Tube Boiler, the Admiralty Three-Drum Boiler was a significant advancement in marine boiler technology during the early to mid-20th century. Much like the earlier Yarrow Boiler, the Admiralty Three-Drum Boiler also used superheater coils. These components were placed in the gas flow path after the steam drum, further increasing the temperature of the steam without raising its pressure. This resulted in drier and more efficient steam production, which enhanced the efficiency of steam turbines and other steam driven machinery. To improve combustion efficiency even further, the latest generation of Admiralty boilers were equipped with a balanced drafting system. Expensive and complex, this system employed forced draft fans to supply air actively to the furnace, ensuring complete combustion of the fuel, while induced draft fans on the other side balanced the air pressure. This ensured optimal air supply and efficient combustion regardless of atmospheric conditions. This system not only increased fuel efficiency but also considerably reduced smoke generation compared to the forced draft system — a critical factor in naval warfare where lack of visibility could be a tactical disadvantage. Much like its predecessors, the Admiralty Boiler featured an even more efficient economizer, which further increased fuel efficiency. The Admiralty Three-Drum Boiler was widely used in Royal Navy ships during World War II and remained in service for many years due to its reliability, robust construction, high efficiency, and excellent steam production capabilities.

Preliminary Values:
Funnel Capacity: 75%

Smoke Interference: 5%

Engine Cost Per Weight: 75%

Engine Vibrations: 10%

Boiler Weight: -25%

Maintenance Cost: 5%

Fuel Efficiency: 50%

Fuel Stowage: -15%