What is the purpose of the steel casing in a packaged watertube boiler?

The primary purpose of the steel casing in a packaged watertube boiler is to form a seal for the furnace. The casing is critical in maintaining the integrity of the combustion chamber by containing the furnace environment, preventing the escape of flue gases, and ensuring that the necessary conditions for combustion are met properly. This sealing capability allows the boiler to operate efficiently and effectively, as it helps to direct the flow of combustion gases through the heat exchange surfaces.

When the casing effectively seals the furnace, it minimizes air infiltration and enhances overall safety, ensuring that the combustion process occurs within a controlled environment. This aspect is particularly important for maintaining the balance of air-fuel ratios, thus supporting optimal combustion efficiency while reducing emissions.

While aspects like structural support and heat transfer are certainly considerations in boiler design, they are not the primary function served by the casing. The casing must also be properly designed to withstand the pressures and temperatures involved in the system, but the sealing of the furnace is crucial for operational efficiency and safety.