At what pressure are the steam drum vents typically closed during startup?

During the startup of a steam boiler, the steam drum vents are typically closed at a pressure of 15 psi. This is primarily to ensure that the system achieves a sufficient pressure to prevent any backflow or loss of steam, while also allowing for enough pressure to facilitate proper operation and safety of the system. Closing the vents at this pressure helps maintain the efficiency of the steam generation process and promotes safety by avoiding the risk of overpressure or uncontrolled steam release.

The selected pressure also aligns with common operating practices in many industrial applications, providing a balance between safety and operational readiness. By closing the vents at this pressure, operators can ensure a stable and controllable environment for steam production.