What is the difference between a gate valve and a globe valve?

What is the difference between a gate valve and a globe valve? Many people believe that gate valves and globe valves have the function of cutting off media, so they are not different when used. What are the differences between gate valves and globe valves in practical applications? Let's take a look at the differences between the two.

1. Gate valves with different structures are more complex in structure than globe valves, and are also larger in height and size. Gate valves are shorter and higher in appearance than globe valves. Especially, opening the stem gate valve requires a higher height of clearance. If the installation position of the customer's valve is limited, it is necessary to carefully select the rising and rising stem gate valves and remind everyone to pay attention.

2. When fully opened, gate valves with different flow resistances pass through the entire flow channel. At this point, the pressure loss during medium operation is very small. The main advantage is that the fluid flow resistance is small. The flow resistance coefficient of ordinary gate valves is approximately 0.08~0.12. Gate valves are usually suitable for working conditions where frequent opening and closing are not required and the gate is kept fully open or closed. They are not suitable for regulating and throttling ordinary globe valves with a resistance coefficient of about 3.5~4.5, and the opening and closing forces are very small. The flow resistance of the shut-off valve throughout its entire stroke is very high, and the required driving force or torque is also much greater. But it is very suitable for regulating and throttling fluids.

3. Gate valves with different flow directions of media inside the valve body have the same effect when viewed from both sides. When installing a shut-off valve, the medium can enter from below and above the valve core. The advantage of medium entering from below the valve core is that the packing is not under pressure when the valve is closed, which can extend the service life of the packing. When the pipeline in front of the valve is under pressure, the packing can be replaced, which is generally only suitable for small diameter globe valves (below DN50). The disadvantage of medium entering from below the valve core is that the driving torque of the valve is relatively large, about 1.05-1.08 times that of the driving torque entering from above. The axial force on the valve stem is large, and the valve stem is prone to bending. Therefore, globe valves with a diameter exceeding 200 millimeters are all designed with medium flowing in from above.

4. The sealing surface of the gate valve has a certain degree of self sealing ability. The valve core is in close contact with the sealing surface of the valve seat through medium pressure, achieving sealing performance and no leakage. The sealing surfaces of the shut-off valve only come into contact with each other when fully closed, and the relative sliding amount between the forcibly closed valve core and the sealing surface is very small, so the wear of the sealing surface is also very small. When the gate valve is opened and closed, the sealing surfaces of the valve core and valve seat always come into contact and friction with each other, so the sealing surfaces are prone to wear. Especially when the valve is close to the closed state, the pressure difference before and after the valve core is very large, and the wear of the sealing surface is even more severe. The wear of the sealing surface of the shut-off valve is mainly caused by debris in the valve core and sealing face, or by medium high-speed erosion caused by inaccurate closing state.

5. The maintenance procedures for different gate valves are not applicable to on-site pipelines, and most globe valves can have their seats and discs replaced online without the need to remove the entire valve from the pipeline. This is very suitable for situations where valves and pipelines are welded together. So when choosing a product, how should the functions of globe valves and gate valves be distinguished? Globe valves have a simpler structure, better sealing, and more convenient manufacturing and maintenance than gate valves. The disadvantage is high fluid resistance and high opening and closing forces.

Gate and globe valves are both fully open and fully closed valves, suitable for shut-off but not suitable for regulating valves. When selecting valves in the application process, attention should be paid to the characteristics of the valves. Globe valves are usually used for small pipelines and better sealing performance. In steam systems and large diameter pipelines, gate valves are suitable due to their low fluid resistance.