According to the ASME code, what should be done with the air cock when warming up a boiler?

The best practice according to the ASME (American Society of Mechanical Engineers) code when warming up a boiler is to keep the air cock closed once the steam pressure reaches a certain level, typically around 25 psi. This procedure helps ensure that no air escapes from the boiler system at this pressure. Keeping the air cock closed during this stage is essential for maintaining proper pressure and preventing the introduction of contaminants or atmospheric air into the system, which could adversely affect boiler operation and efficiency.

The correct response demonstrates an understanding of the operational safety measures required for steam boilers. Properly managing the air cock contributes to the boiler's efficient functioning and helps prevent potential hazards associated with air entering the system, such as oxygen corrosion or equipment inefficiencies. The air cock’s usage is closely tied to the boiler's pressurization and operational stability, illustrating the need for careful monitoring during the startup and warm-up phase.