Why Use a Ball Valve Versus a Globe Valve?

What Is the Main Difference Between Ball and Globe Valves?

The main difference between ball and globe valves is the way they close. Ball valves have a stem and ball, which turns horizontally, and are commonly referred to as "rotational" valves. Whereas, globe valves have a stem and plug, which strokes linearly, and gives them their other name of "stroke" valves. Ball valves are best suited to applications requiring on/off control without pressure drop. While globe valves excel at regulating flow.

How Does a Ball Valve Work?

Ball valves feature a hollow, perforated ball that pivots to control fluid flow. As a type of quarter-turn valve, it allows for quick operation: the valve is open when the ball's hole aligns with the flow and closed when the ball is turned 90 degrees. The handle of the valve provides a clear visual indicator of its status—lying flat in line with the flow when open and perpendicular to it when closed, ensuring easy identification of whether the valve is in operation.

How Does a Globe Valve Work?

A globe valve is an instrument used to stop and/or control the flow of fluids in a pipeline. It works by halting the flow of a fluid through a pipe. The name globe comes about due to the valve’s cylindrical shape. There are usually two halves of the body within the globe valve that are separated by an internal baffle.

Even though globe valves exhibit more pressure drops than gate valves, you can use them where the pressure drop via the valve is a non-controlling factor. Another name for globe valves is throttle valves when they are used for throttling purposes.

Globe valves have long been the industry standard for control valves, recognized by their spherical body shape, which consists of two halves separated by an internal baffle. This baffle features an opening that serves as a seat for a movable plug or disc, which can be screwed in to close the valve. In automated globe valves, smooth stems are commonly used instead of threaded ones, allowing the valve to be opened and closed by an actuator assembly.

How is a Globe Valve Made?

Globe valves are primarily cast due to their complex flow passages, though they can also be constructed from wrought materials for specific applications.

The disc and seat rings are typically made of bronze, while steel globe valves designed for temperatures exceeding 350°C feature stainless steel trims to prevent seizing and galling. Heat treatment of the valve's mating faces is essential to achieve differential hardness values, and other trim materials, such as cobalt-based alloys, may also be used.

To ensure full-bearing surface contact during valve closure, the seating surface must be ground. For lower pressure classes, an extended disk locknut maintains alignment, whereas disc guides are cast into the valve body for higher pressures. Additionally, preventing galling between the disc face and seat ring is achieved by allowing the disc to turn freely on the stem.

Which is Better: Ball Valve or Globe Valve?

Ball valves are known for their durability and reliability, maintaining performance even after numerous cycles and long periods of disuse. These features make them ideal for shutoff applications, often preferred over gate and globe valves. However, ball valves do not provide the fine control in throttling applications that globe valves offer, making the choice dependent on the specific needs of the application.