Understanding Forced Circulation Boilers

A 'Forced Circulation' boiler is a type of boiler where the circulation of water and steam within the boiler tubes is achieved using a circulating pump, rather than relying solely on natural convection currents (density differences between water and steam). This forced circulation allows for higher pressures, better heat transfer rates, and more stable operation, especially in designs like 'once-through' boilers where there is no large water reservoir.

Analysis of Boiler Types

Let's examine each option provided to determine which one is primarily known as a 'Forced Circulation' boiler:

• Benson Boiler: This type of boiler is a high-pressure, water-tube boiler. It is often designed as a 'once-through' boiler, meaning water passes through it only once without recirculation. To ensure adequate flow and prevent overheating, especially at very high pressures and temperatures, a circulating pump is typically employed. Therefore, the Benson boiler is fundamentally a forced circulation system.
• Lancashire Boiler: This is a classic design of a horizontal, cylindrical, fire-tube boiler. It operates at relatively low pressures and relies on natural convection for the circulation of water. It is not a forced circulation boiler.
• Babcock & Wilcox Boiler: This is a common type of water-tube boiler. While many designs operate with natural circulation, some high-pressure or specialized versions might incorporate assisted or forced circulation systems. However, its primary classification is not exclusively as a 'Forced Circulation' boiler like the Benson. It's often associated with natural circulation.
• Cochran Boiler: This is a type of vertical, multitubular, fire-tube boiler. It operates at relatively low to moderate pressures and relies on natural convection for water circulation. It is not a forced circulation boiler.

Identifying the Forced Circulation Boiler

Based on the analysis, the Benson boiler stands out because its operational principle, particularly in its common 'once-through' configuration, inherently requires and utilizes forced circulation via a pump to manage the flow of water and steam efficiently and safely under high pressure conditions.

Therefore, the boiler primarily known as a 'Forced Circulation' boiler among the choices is the Benson boiler.