What is the function of expansion tanks in a boiler system?

• A. To cool down the steam before it enters the system
• B. To accommodate the expansion of water and maintain system pressure
• C. To provide backup water supply during a failure
• D. To filter impurities from the water

Answer: (B)

Expansion tanks play a crucial role in boiler systems by accommodating the expansion of water as it heats up, which is essential for maintaining system pressure within safe and functional limits. As water is heated in a boiler, it expands, and if this expansion were not managed, it could lead to excessive pressure buildup. This pressure increase can damage various system components or cause safety relief valves to activate unnecessarily.

By providing a space for the expanded water to flow into, expansion tanks ensure that the pressure remains stable within the closed-loop system. They typically contain a bladder or diaphragm that separates the water from an air cushion. This air cushion absorbs the increased volume from the expanding water, thus allowing the system to function efficiently and safely. This function is vital in preventing potential overpressurization and maintaining the overall integrity of the heating system.