When opening a high-pressure steam valve into a cold line, the best practice is to:

Opening the valve slowly is important because it allows for a gradual increase in pressure and temperature within the cold line. When high-pressure steam is introduced suddenly into a cold line, it can create thermal shock, leading to rapid expansion and potential damage to the piping system. This method also helps to prevent water hammer—an effect that can occur when steam rapidly condenses back into water, causing shock waves in the system. By opening the valve slowly, you give the system time to adjust to the changes, which enhances safety and protects the integrity of the piping and connections.