Understanding Globe Control Valves

Globe control valves are a type of control valve used to modulate flow in a pipeline or pipelines. Globe valves are named because of their spherical body, with the two halves of the body being separated by an internal baffle. This baffle has an opening which accommodates a seat. The valve can be opened or closed by a plug which is attached to the stem. There are a wide variety of valves that are available to assist systems in flow regulation. Globe valves are one of the options for successfully controlling whether or not a media enters into a section of a process system.
Globe control valves are comprised of a body, stem, bonnet, plug, cage, and seat ring. Globe valves contain a plug, which can also be known as a disc, and the plug moves to block an opening in the internal opening of the valve. The plug prevents media from moving beyond a certain point, or diverts the media to certain areas of the process. In many applications of globe valves, the plug can be used to provide a reliable seal if a soft seat is provided. This option can be expensive. Primarily, globe valves are used to modulate and divert the flow of media to different areas of the process.
The stem component of globe control valves is connected to the plug. The stem provides the actual up and down movement which places the plug in the closed position, or removes the plug and allows an opening to be created. Most companies find that the smooth stem is better for meeting their needs, because it can be automated and connected to either an electric, hydraulic, or pneumatic actuator. Some companies, however, prefer the threaded stem since it allows for the plug to be manually controlled. In these cases, globe valves can be controlled and positioned through the use of a handwheel.
The stem moves through a hole in the bonnet of the valve. Packing is generally used to create and maintain a seal between the bonnet and the stem. The bonnet is also able to provide globe control valves with a pressure-tight seal. Bonnets can be attached to a system with screws or bolts. When considering the type of bonnet that is most appropriate for the context of a company, a business needs to estimate the number of regular cleanings that a bonnet might need, based on the type of liquid flowing through the bonnet and the type of operations that are being performed. Screws are the best choice for connecting globe valve bonnets that might need to be removed frequently for cleaning or other maintenance.
Several different types of materials are available for globe control valves. Metallic alloys are commonly used to fashion the different components of globe valves, but plastics are also an option. Globe valves come in many different material types in order to serve in multiple process loops.