Both globe and gate valves are essential to control components in various piping systems today. Each type of valve differs in appearance, structure, and practical use. However, globe and gate valves have some similarities in appearance; both function as cutting off in the pipeline. Therefore, many people will be confused between the two. However, if you look closely, the difference between the globe and gate valves is still quite significant.
In this article, I will introduce you to the difference between globe valves and gate valves.
1. Different structures
Gate valves and globe valves are shut-off valves, the two most common types of valves.
1.1 Different shapes
The gate valve is taller than the globe valve, and the globe valve is longer than the gate valve for the same bore. In particular, open stem valves require a higher height space.
1.2 Sealing surface
The sealing surface of the gate valve has a specific self-sealing capacity. Its spool by media pressures tightly in contact with the sealing surface of the valve seat to achieve tight not leak.
The wedge gate valve spool slope is generally 3 ~ 6 degrees. When forced to close too much or temperature changes in the spool easy to jam. Therefore, specific measures to prevent the spool jamming are taken in high temperature, high-pressure wedge gate valves in the structure.
1.3 Degree of wear and tear
Gate valve in the opening and closing, the spool and seat sealing surface always contact and mutual friction, so the sealing surface is easy to wear. However, especially when the valve is close to the closed state, the pressure difference between the front and rear of the spool is huge, and the seal surface wear is more serious.
2. Principle of operation
2.1 Globe valve
The globe valve opens and closes with a rising stem, i.e., by turning the handwheel. The handwheel will follow the branch in a rotating and lifting motion. The gate valve is to turn the handwheel so that the stem to do lifting movement, the handwheel itself position unchanged. Flow rates vary, with gate valves requiring full opening or closing while globe valves do not. Globe valves have a defined inlet and outlet direction. Gate valves do not have an inlet or outlet direction.
2.2 Gate valves
In addition, the gate valve is only fully open or fully closed in two states, the stroke of the gate opening and closing is significant, and the opening and closing time is extended. Globe valves have a much more minor plate movement stroke, and the plate can stop at a specific place in the movement to make flow regulation. The gate valve can only be used for cut-off and has no other function.
3. Comparison of gate valve and globe valve characteristics
3.1 Characteristics of gate valves
Fluid flow resistance is negligible.
The ordinary gate valve flow resistance coefficient is about 0.08 ~ 0.12, while the expected resistance coefficient of the globe valve is about 3.5 ~ 4.5.
The opening and closing forces are negligible. Therefore, the medium can flow in both directions.
Complicated structure, large height dimensions, easy wear of sealing surface.
3.2 Characteristics of stop valves
Good sealing performance.
Easy to manufacture and maintain.
Considerable liquid resistance, opening, and closing force.
Gate valve and globe valve belong to the fully open and shut-off type valve, as cut off or connected to the media, and should not be used as a regulating valve.
Their characteristics determine the application range of globe valves and gate valves. When a better shut-off seal is required in smaller channels, we should use more globe valves. We should use gate valves in steam pipelines and large diameter water pipelines as fluid resistance is generally required to be small.
4. Differences in installation methods
4.1 Installation methods for shut-off valves
4.1.1 How the medium enters from underneath the spool
18.104.22.168 Installation advantage
The advantages of this installation method are that the packing is not under pressure when the valve is closed, and it also extends the service life of the filling. And the replacement of the packing can be carried out with the pipeline in front of the valve under pressure.
22.214.171.124 Disadvantages of installation
Its disadvantages are: the driving torque of the valve is more significant, about one times the flow above, the axial force on the valve stem is large, and the branch is easy to bend. So this way is generally only applicable to small diameter globe valves (DN50 below). Therefore, DN200 above the globe valve is selected.
4.1.2 Media from above the way of inflow
The other is the way the medium flows from above. (Electric globe valves are generally used in the way the medium enters from above.) The disadvantages of how the medium enters from above are precisely the opposite of how it enters from below.
4.2 Installation of the gate valve
In the case of limited installation space, we must pay attention to the selection. The gate valve can rely on the medium pressure to close tightly with the sealing surface to achieve the effect of no leakage. Always contact and rub each other when opening and closing the valve spool and seat sealing surface.
Therefore, the sealing surface is prone to wear. In addition, when the gate valve is close to closing, the pressure difference between the front and rear of the pipeline is significant, making the sealing surface wear more serious.
5. Performance differences
5.1 Flow resistance
The globe valve can be used for both cut-off and flow regulation. The fluid resistance of the globe valve is relatively high, and it takes more effort to open and close. However, the opening and closing strokes are short because of the short distance of the valve plate from the sealing surface.
Gate valve because it can only be fully open and fully closed. When it is fully open, the resistance to the flow of the medium in the channel of the valve body is almost 0. However, the gate plate is far from the sealing surface, and the space and closing time are extended.
5.2 Installation and flow direction
Gate valve flow in both directions of effect is the same. Therefore, we do not require advice on import and export during installation. The medium can flow in both directions.
The globe valve, on the other hand, needs to be installed in strict accordance with the direction marked by the arrow on the valve body. There is also an explicit provision on the import and export direction of the globe valve, China’s valve “three to” the flow direction of the globe valve is always used from top to bottom.
Globe valve is low into the high. From the outside, an obvious pipeline is not in a phase of the horizontal line. Gate valve flow path in a horizontal line. The stroke of the gate valve is more significant than the globe valves.