Which of the following types of valves completely closes one side before opening another in a gas system?

The type of valve that completely closes one side before opening another in a gas system is a three-way valve. This valve plays a crucial role in controlling the direction of gas flow within the system. By fully shutting off one path, it can effectively redirect the flow of gas to a different outlet, allowing for systematic control and modifications in various applications.

In operational contexts, a three-way valve is often utilized for applications that require either mixing or diverting gas flows. Its design ensures that when one passage is opened, the other is completely sealed, which helps maintain system integrity and prevents backflow or pressure inconsistencies. This functionality is essential for scenarios where accurate flow direction is critical to the safety and performance of the gas system.

The flow control valve regulates the rate of flow, which doesn't necessarily involve completely sealing one path before opening another, while a check valve allows flow in one direction and prevents backflow but doesn't have the ability to switch between paths. A manual valve requires physical operation to either open or close and does not inherently manage the directional flow like a three-way valve does.