Differences Between Globe Valve and Gate Valve
Globe valves, gate valves, butterfly valves, check valves, and ball valves are integral components in modern piping systems, each serving distinct roles in controlling flow. While they differ significantly in structure and function, globe valves and gate valves share similarities in appearance and their ability to shut off flow within a pipeline, which can confuse those unfamiliar with their nuances. Below is a detailed comparison to clarify these differences.
Structure
Valve selection becomes critical when installation space is limited. A gate valve relies on medium pressure to seal its surface tightly, ensuring zero leakage. However, during operation, the valve core and sealing surface are in constant contact, leading to wear, especially when closing under a significant pressure differential.
Gate valves are structurally more complex than check valves. Visually, gate valves are taller, whereas check valves tend to be longer for the same diameter. Gate valves also come in two designs: rising stem (visible stem movement) and non-rising stem. Check valves lack this distinction.
Working Principle
In a check valve, the stem moves upward when opening, with the handwheel and stem rising together. Conversely, gate valves operate by moving the stem vertically while the handwheel remains stationary. Gate valves must be either fully open or closed, while globe valves allow partial opening for flow adjustment. Globe valves also have specified inlet and outlet directions, unlike bidirectional gate valves.
Gate valves offer two states: fully open or fully closed. Their longer stroke and extended opening/closing times contrast with globe valves, which permit precise adjustments. Check valves also enable partial movement of the valve plate for modulating flow, a function gate valves lack.
Performance
Globe valves serve dual purposes: shutting off flow and enabling fine control. However, they exhibit higher fluid resistance and require more effort to operate. Their shorter stroke and proximity of the sealing surface to the valve plate contribute to faster operation.
In contrast, gate valves minimize flow resistance when fully open, as the medium experiences nearly zero resistance through the valve body. This design makes gate valves easier to operate, though their longer opening/closing distances increase actuation time.
Installation and Flow Direction
Gate valves are bidirectional, with no installation direction requirements, allowing medium flow in either direction. Globe valves, however, must follow the directional arrow on their body for proper installation. In compliance with industry standards, globe valves typically have a top-to-bottom flow direction.
Check valves feature an offset design, where the inlet and outlet are on different planes, unlike the linear flow path of gate valves. Gate valves have a longer stroke compared to globe valves, which impacts flow resistance.
Sealing
The sealing surface of a globe valve is a small trapezoidal area on the valve core. If the core detaches, the valve effectively closes, though the seal may not be perfect under high pressure. Gate valves rely on side sealing via the core’s gate plate, but their sealing performance is generally inferior to that of globe valves. Additionally, a detached gate valve core does not result in automatic closure.
In specific cases, check valves and globe valves allow medium entry from below or above the valve core, depending on operational requirements. Each configuration has distinct advantages and drawbacks regarding torque, stem stress, and packing longevity, making the choice dependent on valve size and application.
