A globe valve is a mechanism used to control or stop the flow of liquid or gas through a pipe. The seat of a globe valve is in the middle of and parallel to the pipe, and the opening in the seat is closed off with a disk or plug. Globe valves can be structured to handle flow in either direction.
A globe valve is formed by a baffle that splits the interior of the pipe, usually parallel to the length of the pipe. The baffle contains an opening that is sealed by means of a disc or flat plug being pushed down into the opening, or seat, perpendicular to the pipe, to stop the flow through the pipe. A structure called a bonnet outside the pipe holds a stem that is connected to the disc. A handwheel at the top of the bonnet is used to manually screw down the stem with the disc at its end until the disc seals against the seat opening. In large industrial applications, a globe valve may be sealed using an electrical, pneumatic, or hydraulic actuator instead of a manual handwheel.
These devices are sometimes referred to as throttle valves because they can reduce the flow through the pipe. If the sealing disc is moved part of the way toward the seat opening, the space through which the product can flow is limited and therefore the flow is limited. This type of valve offers good control to regulate the flow of liquid. Water pipes are often fitted with a globe valve so the operator can control the flow of water through the pipe by opening the valve only partially or all the way.
This valve can also be set up to close with or against the flow of product. If the product flows in the same direction that the disc is closing, the flow will aid the closure of the seal but make opening harder. Conversely, if the flow goes against the direction of the disc closure, it will be easier to open the valve and more difficult to close it.
The baffle inside a globe valve causes the product to divert its direction to move through the baffle. This angled movement means that the product cannot flow as freely and causes a pressure drop after the valve. Globe valves are generally unsuitable for slurries or thicker substances that can be impeded by the baffle.
