Which valve subassembly is considered part of the pressure vessel assembly?

• A. Drive.
• B. Stem.
• C. Body.
• D. Disk.

Answer: (C)

In valve design, the component that actually contains the pressurized fluid and forms the pressure boundary is the valve body. It houses the seating surfaces, interfaces with the piping, and is designed to withstand the internal process pressure, so it’s considered part of the pressure vessel assembly. The drive is just the external actuator, not part of the pressure boundary. The stem transmits motion through the body and must seal, but it isn’t the primary pressure-containing element. The disk is the moving seal that blocks flow against the seat, but the disk itself isn’t the container that holds the pressure. Therefore, the body best fits as the part included in the pressure vessel assembly.