Globe valves are commonly used to control flow in pipelines. Globe valves are governed by the position of a moveable disk (or plug) in relation to the fixed ring seat, as opposed to the "all or nothing" approach of a gate valve. Throttling flow control is the most common application for a globe valve. A throttling globe valve uses a spiral groove on the inside surface of the plug that creates a series of small holes, which allows fluid to pass through but prevents large particles from entering the pipe.
The plug of a globe valve can be rotated by any number of mechanisms, including hand wheels, cranks, and motors. Hand wheeled plugs are easy to operate but require an operator standing near the valve at all times. Motor-operated plugs are convenient because they can be operated from a distance. They also provide fail-safe operation if electricity enters the system through a ground fault or other cause.
For these reasons, motor-operated plugs are generally preferred over hand-wheel plugged valves. However, hand-wheeled plugs are not uncommon in rural areas where electricity is not readily available and their use reduces operating costs. Also, some operators may prefer the tactile feedback provided by a hand-turned plug rather than using a remote-control device.
A globe valve includes an integral stem with either a single or double handle configuration. The stem passes through the side wall of the pipeline and is secured in place by a nut threaded onto it.
The Workings of a Globe Valve The primary function of a globe valve is to stop, initiate, and control flow. It is made up of a moveable disk and a stationary ring seat in a spherical body. The seat of a globe valve is in the centre and parallel to the pipe, and the disk closes up the hole in the seat. When turned by a handle or knob on the outside of the shell, the disk can be moved into and out of contact with the seat. This creates an area of restriction that controls the flow of water through the valve.
Restriction means slowing down the flow rate of water through a conduit or pipe. This is necessary because if all the holes in a pipe were open at once, there would be too much pressure and the pipe would burst. By restricting the flow of water through certain parts of the pipe, less pressure is built up in other parts of the pipe and it is more likely to remain intact.
Globe valves are used for controlling the flow of water in pipes. They are most commonly found in residential plumbing systems but also used in commercial buildings as well. Globe valves have several advantages over other types of valves: they are easy to operate, they provide continuous control of water flow, and they do not need to be opened every time you want to turn off the supply line.
There are two main types of globe valves: double-disk and triple-sphere.
Globe valves are generally employed in circumstances when commodity throttling is necessary. The pace at which the commodity flows through the valve may be changed to any desired level by simply twisting the handwheel. A key aspect of the globe valve is that the valve seat is parallel to the stream of flow. This means that there will be no reverse flow or leakage if the valve is not fully closed.
The term "globe" refers to the shape of the valve's seating surface. It is usually made of brass or bronze and is shaped like a ball. The term "valve stem" is used for the shaft on which the seating surface is mounted. It passes down through the center of the ball and connects it to the mechanism that opens and closes the valve. The valve stem can be turned via a handwheel or other mechanical device, allowing the user to control the amount of fluid that flows through the valve.
Globe valves were commonly used before the advent of precision components. They are still employed in some applications where exact quantities of fluid are not required or where maintenance-free performance is important. Globe valves are also useful as fillers in piping systems, providing easy access to various points without having to shut off the main line completely.
In addition to commercial use, globe valves are common in home plumbing projects such as kitchen and bathroom sinks, tub/showers, and hot-water heaters.
For isolation and throttling functions, conventional globe valves can be employed. Although these valves have slightly larger pressure drops than straight-through valves (e.g., gates, plugs, balls, and so on), they can be employed in situations where the pressure drop through the valve is not a determining issue. Globe valves are available in two basic configurations: the standard configuration and the balanced configuration. In both cases, the flow path through the valve is generally perpendicular to the axis of the stem. However, the orientation of the flow path with respect to the stem differs between the two types of valves.
In the case of the standard globe valve, the stem connects to one end of the flow passage and opens into a spherical cavity that communicates with the other end of the flow passage. The cavity receives an axial load from a compression spring that forces the sphere against any object it contacts. This ensures that the ball will remain seated even if there is some movement of the stem within its bore. Because there is no mechanism for aligning the stem with the flow path, standard globe valves are prone to having some fluid enter the area behind the ball when the valve is shut off. This occurs because there is no way for the fluid to escape past the ball.
The second type of globe valve is the balanced globe valve. Like the standard globe, the balanced globe has a cavity at each end of the flow passage that communicates with the other end via a hole in the center of the sphere.