Final answer:
Three types of valve stem mechanisms are gate valve, globe valve, and ball valve.
Step-by-step explanation:
There are three types of valve stem mechanisms:
- Gate valve: This type of valve has a flat or wedge-shaped gate that moves up and down between two seats to control the flow of fluid.
- Globe valve: This type of valve has a globe-shaped disc that moves up and down to control the flow of fluid.
- Ball valve: This type of valve has a ball-shaped disc with a hole in the center. When the hole is aligned with the flow direction, fluid can pass through the valve.