A globe valve is a type of valve used for regulating flow in a pipeline, consisting of a movable disk-type element and a stationary ring seat in a generally spherical body.
Globe valves are named for their spherical body shape with the two halves of the body being separated by an internal baffle. The plug is also called a disc or disk. In globe valves, the plug is connected to a stem which is operated by screw action using a handwheel in manual valves. Typically, automated globe valves use smooth stems rather than threaded and are opened and closed by an actuator assembly.
Globe valves may have flanged ends which are drilled according to pipeline compatible flange dimensional standards. Also can be Butt weld and Socket Weld connection.
Although globe valves in the past had the spherical bodies which gave them their name, many modern globe valves do not have much of a spherical shape. In plumbing, valves with such a mechanism are also often called stop valves since they don't have the global appearance, but the term stop valve may refer to valves which are used to stop flow even when they have other mechanisms or designs.
Globe valves are used for applications requiring throttling and frequent operation. For example, globe valves or valves with a similar mechanism may be used as sampling valves, which are normally shut except when liquid samples are being taken.
The body is the main pressure containing structure of the valve and the most easily identified as it forms the mass of the valve. It contains all of the valve's internal parts that will come in contact with the substance being controlled by the valve. The bonnet is connected to the body and provides the containment of the fluid, gas, or slurry that is being controlled.
Globe valves are typically two-port valves, and ports are openings in the body for fluid flowing in or out. The two ports may be oriented straight across from each other or anywhere on the body, or oriented at an angle (such as a 90°). Globe valves with ports at such an angle are called angle globe valves. Angle type globe valves are mainly used for corrosive or high viscous fluids which solidify at room temperature. This is because straight valves are designed so that the outlet pipe is in line with the inlet pipe and the fluid has a good chance of staying there in the case of horizontal piping. In the case of angle valves, the outlet pipe is directed towards the bottom. This allows the fluid to drain off. In turn, this prevents clogging and/or corrosion of the valve components over a period of time. A globe valve can also have a body in the shape of a "Y". This will allow the construction of the valve to be straight at the bottom as opposed to the conventional pot type construction (to arrange bottom seat) in case of other valves. This will again allow the fluid to pass through without difficulty and minimizes fluid clogging/corrosion in the long term.
The bonnet provides a leakproof closure for the valve body. Globe valves have a union, or bolted bonnet. Union bonnet is suitable for applications requiring frequent inspection or cleaning. It also gives the body added strength. A bonnet attached with bolts is used for larger or higher pressure applications. The bonnet also contains the packing, a wearable material that maintains the seal between the bonnet and the stem during valve cycling.
Globe valves are typically constructed from, cast carbon steel, stainless steel, alloy steels, forged steels, Hastelloy, Monel, Inconel and others.
Packing material must also be considered during valve selection. Typically the requirement for a low friction packing conflict with a durable material that will provide low maintenance requirements during service life. Corrosive applications can further complicate packing material selection as the typical packing materials may or may not be compatible with the processed materials. Typically graphite or PTFE is used due to its low friction coefficient. Enviro-seal applications also have the availability of constant applied force (live-load) packing. While more complex, it allows for constant packing force load throughout the life of the packing material. This packing helps meet contemporary environmental laws.