Whether to choose a ball valve or a globe valve comes down to whether the main purpose in that piping is to “stop or allow flow” or to “finely regulate flow rate.” For shutoff applications where you want to switch quickly and reliably between fully open and fully closed, a ball valve is suited; for regulating applications where you want to change the opening degree to throttle the flow, a globe valve is suited. The two differ in structure and in their pressure-loss tendencies, and mistaking the purpose can lead to valve wear, cavitation, or degraded controllability.
Key points of this article
- The basic idea is a ball valve when shutoff and full-open/full-close are the main purpose, and a globe valve when flow regulation is the main purpose
- A ball valve has low pressure loss when fully open, while a globe valve is strong in throttling control and tight shutoff
- Organizing the application, fluid, frequency, and adjustment range as conditions makes it harder to err in selection
Differences in structure and characteristics between ball valves and globe valves
How each works
A ball valve has a structure in which a spherical disc with a through-hole is rotated 90 degrees to open and close. When fully open, the flow path is nearly straight, so pressure loss is generally low and it is suited to quick opening and closing. On the other hand, throttling operation with the handle held at an intermediate opening tends to cause uneven wear of the seat and seat ring, and as a rule is not recommended.
A globe valve has a structure in which the disc is moved up and down relative to the seat to change the gap in the flow path. Because the flow describes an S-shape, pressure loss is relatively large even when fully open, but the flow rate changes smoothly according to the opening degree, giving it excellent throttling control and tight shutoff.
Criteria for selection
First, divide the application into “shutoff-centered” or “regulation-centered.” A globe valve is easy to use for bypass adjustment on the suction and discharge sides of a pump or for fine adjustment of steam or hot-water temperature and flow rate, while a ball valve tends to be easier to handle when used fully open or fully closed as an equipment root valve or a shutoff valve for maintenance.
Next, organize the opening/closing frequency, operating speed, fluid properties (gas or liquid, presence of slurry or foreign matter), required adjustment range, and severity of the shutoff requirement as conditions. Because the weighting of these changes with the piping conditions, there is no single universal answer, and it is practical to compare them only as a guide.
Points to note during selection
Avoiding throttling operation and misuse
Using a ball valve at an intermediate opening for a long time can cause localized wear of the seat material, vibration, and reduced sealing performance. Conversely, using a globe valve merely as a shutoff valve in large diameters and at high frequency can be disadvantageous in terms of pressure loss and operating torque. Selecting a valve type that matches the purpose tends to be advantageous for both service life and controllability.
Review based on fluid conditions
Throttling under high differential pressure raises concerns of cavitation and erosion, and in this case the valve type, diameter, and material need to be reviewed according to the conditions. The figures and suitability are general tendencies, and for actual selection we recommend examining each case individually based on conditions such as flow rate, pressure, temperature, and fluid name.
Frequently asked questions
Q1. Which is better suited to flow regulation?
A1. In general, a globe valve, whose flow rate changes smoothly according to the opening degree, is suited to flow regulation. Regular use of a ball valve at an intermediate opening is not readily recommended.
Q2. What if I want to keep pressure loss low?
A2. For pressure loss when fully open, a ball valve, whose flow path is nearly straight, tends to be lower. It tends to be advantageous for shutoff applications.
Q3. Which has better tight shutoff (less leakage)?
A3. Both are used for shutoff applications, but the choice changes with the conditions. Depending on the required leakage rate and the fluid, selection of an appropriate valve type and seat material is necessary.
Q4. Which is better for locations that are opened and closed frequently?
A4. A ball valve, which can be operated quickly with a 90-degree turn, is often easier to handle. However, also check the operating torque and diameter.
Q5. Is it a problem to change the valve type when replacing an existing valve?
A5. Suitability changes depending on whether the application is shutoff or regulation. Because a careless replacement affects controllability and loss, we recommend examining it after organizing the conditions.
Q6. Which one is for fluids containing slurry or foreign matter?
A6. The appropriate structure and material differ depending on the fluid properties. Because there is also a tendency for foreign matter to become caught, individual examination based on the fluid conditions is necessary.
Summary
Ball valves and globe valves are basically chosen along the axis of “whether the main purpose is shutoff or regulation.” Start from a ball valve for full-open/full-close shutoff and a globe valve for throttling and adjusting the flow, then make the judgment by layering on conditions such as opening/closing frequency, fluid, differential pressure, and adjustment range.
If you have concerns such as “I know the required flow rate but am unsure about controllability in the minimum-flow range,” “I am worried about cavitation when throttling under high differential pressure,” or “I want to select an equivalent product for an existing valve or an appropriate valve type,” please make use of Yoshitake’s technical and selection consultation after organizing the conditions. Based on information such as the application, fluid, pressure, and diameter, we will help you consider a suitable valve type.