What is the main role of boiler air cock valves during boiler filling?

The primary function of boiler air cock valves during the filling of a boiler is to allow trapped air to escape. When a boiler is filled with water, air can become trapped in various areas of the system, which can lead to inefficiencies and operational issues. If this air is not removed, it can cause problems such as reducing the boiler's efficiency and potentially creating areas of low pressure or damaging the system.

By opening the air cock valves, the trapped air can vent out, ensuring that the water can fill the boiler effectively. This process is critical for maintaining proper pressure and ensuring that the boiler operates efficiently when it is heated. The removal of air not only allows for effective filling but also helps prevent the formation of air pockets that could lead to further complications while the boiler is in operation.

While other answers may have some relevance to boiler operation, they do not specifically address the essential role of air cock valves during the filling process. For instance, increasing water temperature relates more to the heating phase rather than the filling phase, preventing water hammer involves measures taken during operation to manage flow and pressure changes, and controlling steam pressure pertains to the functioning of the boiler rather than the initial filling process.