How is steam pressure usually controlled in a low-pressure boiler?

In a low-pressure boiler, steam pressure is typically controlled by adjusting the fuel supply and utilizing modulating controls. This method allows for precise management of the combustion process, which directly influences the steam generation rate and, consequently, the steam pressure in the system. By modulating the fuel supply, the boiler can respond to changes in steam demand, ensuring that sufficient steam is produced without exceeding safe pressure limits. This control method is preferred for its efficiency and ability to maintain stable operation under varying load conditions.

Other methods, such as altering the water temperature, do not have a direct and effective influence on steam pressure control. Manual operation of valves can be unreliable and lacks the responsiveness required for maintaining consistent pressure. Increasing the size of the boiler is impractical as a control strategy; it may not address the immediate pressure control needs and could lead to unnecessary costs and resource use. Hence, utilizing modulating controls combined with fuel supply adjustments is the most effective and efficient way to maintain steam pressure in a low-pressure boiler system.