Nov.07.2024
Globe valve VS gate valve: Globe valves and gate valves are similar in appearance, and both function as cutoffs in the pipeline, so many people confuse the two. This article will compare the two from the structure, working principle, performance, etc.
01 Globe Valve VS Gate Valve Structure
When selecting in limited installation spaces, attention should be paid to the type of valves. Gate valves can tightly close and seal against the sealing surface due to the medium pressure, achieving a leak-proof effect. When opening or closing, the valve core and the seat sealing surface always contact and rub against each other, making the sealing surface susceptible to wear. When the gate valve is nearly closed, the pressure difference before and after the pipeline is significant, causing more severe wear on the sealing surface.
The structure of a gate valve is more complex than that of a globe valve. Visually, under the same caliber, a gate valve is taller than a globe valve, while a globe valve is longer than a gate valve. Additionally, gate valves can be classified into rising stem and non-rising stem, whereas globe valves do not have this distinction.
02 Globe Valve VS Gate Valve Operating Principles
Globe valves operate with a rising stem mechanism, meaning that when the handwheel is rotated, the handwheel rotates and moves up and down along with the valve stem. In contrast, gate valves involve rotating the handwheel to move the valve stem up and down while the position of the handwheel remains unchanged. Their flow characteristics differ: gate valves require full opening or closing, while globe valves do not. Globe valves have specified inlet and outlet directions, whereas gate valves do not.
Globe Valve Working Principle
Furthermore, gate valves have only two states: fully open or fully closed, with a large stroke and long operating time. In contrast, the disc of a globe valve has a much smaller movement stroke, and the disc can be stopped at any point during its movement for flow regulation. Gate valves are only used for shut-off and have no other functions.
Gate valve working principle
03 Globe Valve VS Gate Valve Performance Differences
Globe valves can be used for shut-off and flow regulation. They have higher fluid resistance, making them more labor-intensive to operate, but due to the short distance between the disc and the sealing surface, the stroke is short.
Gate valves, since they only operate in fully open or fully closed states, have almost zero fluid flow resistance when fully open. Thus, they are very easy to operate. However, due to the longer distance between the gate and the sealing surface, the opening and closing time is longer.
04 Globe Valve VS Gate Valve Installation and Flow Direction
The flow direction of gate valves is the same in both directions, and there is no requirement for inlet and outlet directions during installation; the medium can flow bidirectionally. Globe valves, however, must be installed strictly according to the direction indicated by the arrow on the valve body. In China, the "Sanhua Gei" standard specifies that the flow direction of globe valves should always be from top to bottom.
Globe valves have a lower inlet and a higher outlet, which is visually evident as the pipes are not aligned horizontally. The flow channels of gate valves are on the same horizontal line. The stroke of gate valves is larger than that of globe valves.
From a flow resistance perspective, gate valves have lower flow resistance when fully open, while globe valves have higher flow resistance. The flow resistance coefficient of a standard gate valve is approximately 0.08-0.12, requiring less force to open and close, and the medium can flow in both directions. The flow resistance of a standard globe valve is 3-5 times that of a gate valve. To achieve a seal, force must be applied to close it. The disc of a globe valve only contacts the sealing surface when fully closed, resulting in minimal wear to the sealing surface. Due to the larger driving force required, globe valves equipped with actuators should pay attention to torque control adjustments.
There are two installation methods for globe valves. One allows the medium to enter from below the valve core. The advantage is that when the valve is closed, the disc is not under pressure, extending the disc's lifespan and facilitating disc replacement under pressure. The downside is that the driving torque of the valve is about twice that of the upward flow, and the axial force on the valve stem is large, making the valve stem prone to bending. This method is generally only suitable for small-diameter globe valves (below DN50), while globe valves above DN200 typically use the method where the medium enters from above. (Electric globe valves generally use the method where the medium enters from above.) The disadvantages of the upward flow method are opposite to those of the downward flow method.
A gate valve (gate valve) is a shut-off device with a gate disc. The movement direction of the gate disc is perpendicular to the fluid direction. Gate valves can only be fully opened or fully closed and cannot be used for regulation or throttling.
