What are the four types of control valves?

What are the four types of control valves?

• A. Outside stem & yoke
• B. Post indicator valve
• C. Wall post indicator valve
• D. Post indicator valve assembly

Answer: (A)

The key idea here is distinguishing valve designs by how the stem is arranged and how that affects control. An outside stem and yoke arrangement means the valve’s stem sticks out above the bonnet and is fastened to a yoke nut, making it easy to attach an actuator or handwheel and to connect control devices directly. This design is characteristic of valves used for actual flow control, where precise actuation and easy external connection are important. Post indicator valves and the wall/post indicator valve assemblies are built primarily to indicate the position of an underground or exposed valve (open or closed) rather than to regulate flow. They’re focused on visibility and isolation for distribution systems, not on serving as the active control element in a control loop. That’s why they’re not considered control valves. So, the outside stem & yoke type is the best answer because it describes the valve arrangement commonly used for control purposes, whereas the indicator valves are built for status indication rather than active control.

The key idea here is distinguishing valve designs by how the stem is arranged and how that affects control. An outside stem and yoke arrangement means the valve’s stem sticks out above the bonnet and is fastened to a yoke nut, making it easy to attach an actuator or handwheel and to connect control devices directly. This design is characteristic of valves used for actual flow control, where precise actuation and easy external connection are important.

Post indicator valves and the wall/post indicator valve assemblies are built primarily to indicate the position of an underground or exposed valve (open or closed) rather than to regulate flow. They’re focused on visibility and isolation for distribution systems, not on serving as the active control element in a control loop. That’s why they’re not considered control valves.

So, the outside stem & yoke type is the best answer because it describes the valve arrangement commonly used for control purposes, whereas the indicator valves are built for status indication rather than active control.