Figure 1: Globe valve (left) and ball valve (right)
Globe valves and ball valves are both shut-off valves typically used in piping systems. However, it is usually not immediately obvious which valve is most suitable for an application. System design should be finished before valve selection in order to select the best valve for the job in terms of cost, installation space, flow control, and more. Keep reading to learn more about how a globe valve may be more suitable than a ball valve and vice versa.
Figure 2: A globe valve in the open position (left) and the closed position (right) with the valve body (A), bonnet (B), stem (C), and plug (D).
A globe valve is a multi-turn valve, meaning that the handwheel needs to be turned more than 360° to fully open or close the valve. The main components of a globe valve are the valve body, bonnet, handwheel, stem, and plug. Media flows into the valve body (Figure 2 labeled A) through an inlet and exits the valve body through an outlet. The bonnet (Figure 2 labeled B) protects the threaded components of the valve and attaches to the valve body. As the user turns the handwheel, it turns the threaded stem (Figure 2 labeled C), which raises or lowers the plug (Figure 2 labeled D). Raising the plug opens the orifice, thereby allowing media flow. Lowering the plug into the valve seat seals the orifice, preventing the flow. Raising the disc, on the other hand, increases the flow rate. The flow rate is maximum when the disc is raised to its maximum position. The fluid flow rate is controlled by moving the disc proportionally through the stem.
Figure 3: Ball valve parts; Stem (A), ball (B), seat (C), o-rings (D), and valve housing (E)
A ball valve is a quarter-turn valve, meaning that the handle only needs a 90° turn to fully open or close the valve. The main components of a ball valve are shown in Figure 3. The stem (A) connects to the ball (B). The ball sits on the ball valve seat (C), creating the seal. O-ring stem seals (D) are used to prevent leakage. All of these components are within the valve housing (E). As seen in Figure 3, the ball has a bore running through it. Under normal operation, the bore is either aligned with the valve ports to allow flow, or perpendicular to the ports to block flow. Read our article on ball valves for more details on how they work.
Globe and ball valves are both used to turn on or off the flow. Globe valves, though, can also function in a partially open or closed state to modulate the flow. This flow regulation is achievable due to the globe valve’s disc sitting parallel to the flow. The linear flow rate achieved by globe valves is higher than that achieved by ball valves, and reduces the effects of water hammer.
Globe valves have significantly higher pressure loss (head loss) in the fully open position than ball valves. This is because the fluid has to change direction multiple times as it passes through a globe valve.
Globe valves are available in three basic configurations: T- or Z globe valve, Y-globe valve, and angle globe valve. Read our article on globe valves for more information on each type.
The ball valve can be classified into different categories depending on its housing structure, ball design, and port size. Depending on the housing structure, we can have 1, 2, or 3-piece ball valves. Depending on the port size, ball valves are categorized as full port ball valves, standard port ball valves, or reduced port ball valves. And depending on the number of ports, ball valves are classified into 2-way and multiport valves.
Figure 4: Globe valve symbols: globe (A), hand operated (B), pneumatic (C), motor operated (D), hydraulic operated (E).
The symbols for a ball valve are shown in Figure 5. For more details on the symbols of various ball valve configurations, read our article on ball valve symbols.
Figure 5: Actuated ball valve symbols; manually operated ball valve (A), pneumatically actuated ball valve (diaphragm type) symbol (B), pneumatically actuated ball valve (rotary piston type) symbol (C), electrically actuated ball valve symbol, and a hydraulic actuator ball valve symbol (D).
Globe valves are used to control fluid flow. Furthermore, globe valves are advantageous in applications requiring precise throttling. Ball valves, on the other hand, are commonly used for plumbing system shut-off and isolation. Industrial applications for globe valves include fuel oil systems and cooling water systems, while those of ball valves include chemical storage and natural gas industries.
Globe valves and ball valves share some similarities. Both valves are used in piping systems to control the flow of liquids and gasses. Both are shut-off valves designed to allow or block the fluid flow within a pipe. Globe valves and ball valves can be operated manually or automatically.
The selection between a ball valve and a globe valve depends on the intended purpose. The main factors to consider during the selection process are discussed below:
Globe valves are used commonly to control water flow in irrigation systems, regulate airflow in AC systems, and control oil flow in pipelines.
The ball valve has a hollow ball that rotates inside the valve, whereas the globe valve has a disc that moves vertically through the valve stem.
This depends on the intended application. Globe valves are better for throttling applications, while ball valves offer better performance as shutoff valves.
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