What type of valve is used to control the discharge of gas from high-pressure systems?

The correct answer focuses on the role of controlled valves in managing the discharge of gas from high-pressure systems. Controlled valves are designed to regulate flow more effectively than manual options, providing precise control over gas discharge. This capability is vital in high-pressure environments to ensure safety and efficiency, as they can open and close in response to specific system demands or pressure levels.

Controlled valves often include features like automation and sensors that monitor system conditions, providing real-time adjustments to gas flow. This helps prevent system overloads and facilitates safe operation by maintaining the desired pressures and flow rates.

In contrast, while a manual valve can control flow, it lacks the responsiveness and precision required in high-pressure applications. Pressure-relief valves serve a different purpose, focusing on safety by preventing excess pressure buildup rather than managing regular discharge flow. Specialized venting valves may be designed for unique tasks but do not typically offer the comprehensive control required in standard operational settings, making them less suitable as a primary discharge valve in high-pressure systems.