A globe valve is comprised of two halves, separated by an opening with a moveable plug or disc that can be screwed in, or unscrewed to open and close. They’re most commonly used to open, close, or throttle flow in a system.
All globe valves are designed with a stem that moves up and down to regulate flow inside the valve, contains a disc (ball, composition, or plug), and seat which is generally screwed into the valve body. Seats are designed in plane parallel or inclined to the line of the flow.
There are three basic globe valve body designs: Tee, Angle, and Wye. based on the type of body. But this is not the only way of categorizing the globe valves. They also can be divided into external thread types and internal thread types. Also, a globe valve can be divided into a straight flow type and a flow direction angle. Moreover, we can separate globe valves according to the shape of the sealing by product size and type of bellow dressing.
Tee Pattern globe valves, as the first globe valve types, have the lowest flow rate and a higher pressure drop. This is used in extreme throttling systems, for instance in bypass lines around a control valve. For applications where pressure drops are not an issue and throttling is required, tee-pattern globe valves can also be used.
The Wye pattern globe valves give the least flow resistance among globe valves. When completely open, the seat and stem are at a 45° angle, resulting in a straighter flow path with the least resistance to flow. Despite extreme erosion, they are broken open for long periods. They are commonly used in seasonal or start-up operations for throttling. When used in drain lines usually close, they can be barred to avoid debris.
Z-type Globe Valves. A Z-body is the simplest and most frequent sort of globe valve types. The seat is contained within the globular body by a Z-shaped wall. Because of the seat’s horizontal sitting configuration, the stem and disk can wander perpendicular to the pipe axis, resulting in a very large pressure loss. The valve seat is easily accessible via the bonnet, which is coupled to a big aperture at the valve body’s top. The stem acts as a gate valve, passing through the bonnet. This design makes production, installation, and repair easier. When pressure drop is not a problem and throttling is necessary, this style of valve is employed.
Angle Globe Valve
The third type among globe valve types is the angle globe valve that represents a shift in the configuration of the Z-shaped basic glove valve. The entry and exit ends are located at the right angles. The diaphragm may be a plain flat plate with its ends at right angles. The fluid can flow down more symmetrically than discharge from the ordinary globe with just one turn in 90. The angle body style has a particular benefit as it can be used as both a valve and a pipe elbow. The angle valve closely resembles the ordinary globe for moderate pressure, temperature, and flow conditions.
The angle globe valve can be used to control the slugging effect in fluctuating flow conditions. In terms of fluid mechanics and erosion, the release conditions of the angle valve are favorable. In high-pressure applications, these features are extremely important. The valve operates more or less like the Z Shaped Valve under mild conditions.
Globe valves are ideal whenever you need to modulate flow, but you don’t have to worry about the amount of pressure loss. Some applications include:
Cooling water systems
Fuel oil systems
Feedwater and chemical feed systems
Turbine lubricating oil systems
Drain and trim applications in fire sprinkler or other water-based fire protection systems
Globe valves adjust flow, but be careful of the pressure application
When building a piping system, it’s important to choose the right components for the job, which is especially true with valves. Because globe valves force water to change directions even when fully open, they create comparatively large pressure losses. One of the core advantages of globe valves, however, is their ability to modulate water flow. They can be open, partially open, or closed.
Gate valves and ball valves, two alternatives to globe valves, cause minimal pressure losses. However, they don’t provide throttling services like globe valves. For applications where pressure is at a premium, gate or ball valves are better choices than globe valves.
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