A globe valve is a type of valve used to start, stop, and/or regulate flow in a pipeline. The valve has a movable disk-type element and a stationary ring seat within the valve body and it is effective in throttling flow and allowing for precise control. The name globe valve is from its spherical body shape.

Applications of globe valve

Globe valves are the optimal choice for applications requiring precise flow modulation, where pressure loss is not a critical concern, including scenarios such as:

Cooling water systems

Fuel oil systems

Feedwater and chemical feed systems

Boiler and main steam vents and drains

Turbine lube oil system

Drain and trim applications in sprinkler systems (not as control valves in fire sprinkler systems, where pressure is at a premium)

Globe valve flow characteristics

Globe valves exhibit distinct flow characteristics that are pivotal in their selection and application in fluid control systems. These characteristics are primarily defined by the valve's inherent flow coefficient (Cv), flow curve, and the relationship between the valve lift and flow rate under varying pressure conditions.

Inherent flow coefficient (Cv)

The globe valve Cv value represents the valve's flow capacity, indicating the volume of fluid that can pass through with a one psi pressure drop. Globe valve flow coefficient is typically low due to their design, which prioritizes precise flow control over high flow capacity.

Flow curves: linear vs equal percentage

Linear flow curve: Offers a direct proportion between valve lift and flow rate, suitable for applications with constant pressure drop.

Equal percentage flow curve: Provides an exponential relationship between valve lift and flow rate, ideal for varying pressure drop conditions, enhancing control precision.

Proper sizing is crucial to match the valve's flow characteristics with the application's requirements, ensuring efficient operation. The choice between linear and equal percentage depends on the system's pressure dynamics and control needs.