Automatic control applied to modern high-pressure boilers

The developments in boiler design necessitated by the employment of high steam pressure and temperature have increased the sensitivity of the boiler unit to variations in firing rate. As a result the duties of the operator have become more onerous, and reliance on the skill of the individual renders the performance of the plant dependent on the human element. Recognition of the limitations imposed on plant efficiency by the intervention of the boiler operator has led to many plants being equipped with automatic devices to execute routine readjustments in fuel and air supply and feed-water flow. The paper describes an air-operated system of automatic boiler control, though the principles stated apply equally to systems using other types of motive power. The equipment described has proved to be reliable in operation and, apart from the improved technical performance over manual control, has increased the overall efficiency of boiler plants so equipped. Apart from the automatic control of stoker and pulverized-fuel-fired boilers, devices for the control of steam temperature, water level and feed-pump protection are also described.