In valve construction, which element is considered part of the pressure boundary and described as the main body?

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

Answer: (D)

In valve construction, the pressure boundary is the part that actually contains the process fluid under pressure. The main body is the primary pressure boundary because it forms the shell that encloses the internal passages and provides the structural containment against the internal pressure. It is designed to withstand that pressure and keep the system sealed. The drive (actuator) is outside the pressure boundary and only moves the valve; the stem is a moving shaft that traverses the boundary but does not itself form the primary containment; and the disk is the sealing element that blocks flow but is not the main structure that holds the pressure.