Five Key Differences Between Gate Valves and Globe Valves

Five Key Differences Between Gate Valves and Globe Valves

Gate valves are primarily used for fluid shut-off, with the entire flow path being straight through when fully open, resulting in minimal pressure loss during operation. Gate valves are typically suitable for applications where frequent opening and closing are not required, and maintaining the gate fully open or fully closed is necessary. They are not suitable for throttling or regulating flow. For high-velocity fluid, partial opening of the gate can cause gate vibration, potentially damaging the gate and seat sealing surfaces.

In contrast, the principle of globe valves involves applying downward pressure to the sealing surface using the valve stem torque, ensuring tight contact between the valve sealing surface and the seat sealing surface to prevent media flow or regulate flow rate. Globe valves feature a cylindrical valve body with sealing surfaces that are flat or conical, and the valve moves linearly along the fluid's centerline.

Differences between globe valves and gate valves:

Structural Variations:
Gate valves rely on fluid pressure to tightly close against the sealing surface, which can result in leakage if not properly closed. The friction and wear between the gate and seat sealing surfaces are significant, particularly when the gate valve is nearly closed and subjected to high pressure differentials.
Gate valves have a more complex structure compared to globe valves. Visually, gate valves are taller than globe valves for the same nominal diameter, with globe valves being longer. Additionally, gate valves can have rising or non-rising stems, while globe valves do not.

Operating Principles:
Globe valves feature a rising stem design, where turning the handwheel causes both rotational and upward/downward movement of the stem. In contrast, gate valves feature a non-rising stem design, where turning the handwheel only causes upward/downward movement of the stem, with the handwheel position remaining unchanged. The flow capacities differ, with gate valves requiring full opening or closing, while globe valves do not. Globe valves have specified inlet and outlet directions, whereas gate valves do not have directional requirements.

Performance Characteristics:
Globe valves can be used for both shut-off and flow regulation. They offer high fluid resistance and require significant effort to operate due to their short stroke length.
Gate valves, on the other hand, are limited to full opening or closing. When fully open, gate valves exhibit minimal fluid flow resistance, resulting in easy operation. However, due to the greater distance between the gate and sealing surfaces, gate valves have longer operating times.

Installation and Flow Direction:
Both directions of flow are equally effective for gate valves, with no inlet or outlet direction requirements, allowing bidirectional flow. In contrast, globe valves must be installed according to the direction indicated by the arrow on the valve body. Additionally, Chinese valve industry standards require globe valves to be installed with the flow entering from the top.
Gate valves typically have a low-inlet and high-outlet configuration, with a noticeable difference in pipe alignment compared to globe valves, which have a straight flow path. Gate valves offer lower flow resistance when fully open, while globe valves have higher flow resistance. The flow resistance coefficient of ordinary gate valves is approximately 0.08-0.12, resulting in minimal opening and closing force requirements, allowing flow in both directions. For globe valves, the flow resistance is 3-5 times higher than that of gate valves. Forced closure is required for sealing during operation, minimizing seat wear. Actuators should be carefully selected for globe valves due to the higher flow resistance.

Stem Seal:
Globe valves feature a small trapezoidal sealing surface on the valve core (depending on the core's shape). If the valve core becomes dislodged, it acts as a valve closure (although it may not seal tightly under high pressure differentials, it provides good check valve functionality). In contrast, gate valves rely on the side of the gate for sealing, which is less effective than in globe valves. Even if the gate is dislodged, the valve does not close as effectively as globe valves.