Globe valve

This has an opening that forms a seat onto which a movable plug[2] can be screwed in to close (or shut) the valve.

Typically, automated globe valves use smooth stems rather than threaded and are opened and closed by an actuator assembly.

The bonnet is connected to the body and provides the containment of the fluid, gas, or slurry that is being controlled.

Globe valves are mainly used for corrosive or highly viscous fluids that solidify at room temperature.

Union bonnet is suitable for applications The valve's closure mechanism involves plugs that connect to a stem, which is adjusted either by sliding or screwing it up or down to regulate flow.

Unbalanced plugs, typically solid, are suitable for smaller valves or those with low pressure drops.

They offer advantages such as simpler design, with potential leakage only at the seat, and usually lower cost.

However, they are limited in size, as larger unbalanced plugs may require impractical forces to seal and control flow.

In addition, the stem must be very straight, or have low run-out, in order to ensure good valve closure.

This minimum run-out also minimizes wear of the packing contained in the bonnet, which provides the seal against leakage.

As the plug is moved, more of the openings in the cage are exposed and flow is increased and vice versa.