Valve packing surrounds which part of a valve?

The correct answer is the stem because valve packing is specifically designed to create a seal between the valve stem and the valve body. The valve stem is the component that moves up and down or side to side to open or close the valve. Packing, typically made of materials like PTFE or other types of fiber, is used to prevent leaks along this moving part. Proper packing ensures that the valve operates efficiently and safely by minimizing the escape of fluids or gases, which is crucial in maintaining system integrity and performance.

In contrast, the body of the valve is the main structure that houses the internal components, the handle is used for manual operation of the valve, and the seat is the surface where the valve closes against to stop the flow. These parts play vital roles in valve function, but it is the stem that specifically requires the packing to ensure a proper seal during operation.