Simply put, an electric valve is a valve controlled by an electric actuator to achieve the opening and closing of the valve. It can be divided into two parts: the upper part is an electric actuator, and the lower part is a valve. The action force distance is larger than that of electric valves, and the opening and closing speed of electric gate valves can be adjusted. The structure is simple and easy to maintain. During the action process, due to the buffering characteristics of the gas itself, it is not easy to be damaged due to jamming. However, there must be an air source, and its control system is also more complex than that of electric valves. Electric globe valve and flange gate valve belong to the same type of valve, consisting of electric actuator or pneumatic actuator and globe valve. The difference is that its closing part is a valve body, and the valve body rotates around the centerline of the valve body to achieve opening and closing. Gate valves are mainly used in pipelines to cut off, distribute, and change the flow direction of the medium. Two piece ball valve and three piece ball valve are a new type of valve widely used in recent years.
1. Different sealing surfaces
When the gate valve is opened and closed, the valve core and seat sealing surface always come into contact and rub against each other, so the sealing surface is prone to wear, especially when the valve is close to the closed state, the pressure difference between the valve core and the front and back is large, and the sealing surface wear is even more severe; Once the valve disc of the globe valve is in an open state, there is no longer contact between its seat and the sealing surface of the valve disc, so its sealing surface has less mechanical wear. However, if the medium contains solid particles, it is easy to damage the sealing surface. The sealing surface of the gate valve has a certain degree of self sealing ability, and its valve core tightly contacts the sealing surface of the valve seat with the pressure of the medium, achieving tightness without leakage. The slope of the valve core of a wedge gate valve is generally 3-6 degrees. When the valve core is forced to close excessively or has significant temperature changes, it is easy to get stuck. Therefore, measures have been taken to prevent the valve core from getting stuck in the structure of high-temperature and high-pressure wedge gate valves. The sealing surface of the globe valve must be forcefully closed to achieve sealing. Under the same caliber, working pressure, and driving device, the driving torque of the globe valve is 2.5-3.5 times that of the gate valve. This should be noted when adjusting the torque control mechanism of electric valves. The sealing surfaces of the shut-off valve only come into contact with each other when fully closed. The relative slip between the forcibly closed valve core and the sealing surface is very small, so the wear of the sealing surface is also very small. The wear of the sealing surface of the shut-off valve is mostly due to debris in front of the valve core and sealing surface, or due to the non tightness of the closed state, which causes high-speed flushing of the medium.
2. Different structures
Gate valves have a more complex structure and larger height dimensions than globe valves. From the appearance, gate valves are shorter and higher than globe valves, especially rising stem gate valves that require higher height space. This should be noted when selecting in situations where installation space is limited.
3. Different flow resistance
When the gate valve is fully open, the entire flow path is straight, and the pressure loss of the medium during operation is minimal. Compared with the globe valve, its main advantage is that the fluid flow resistance is small. The flow resistance coefficient of a regular gate valve is about 0.08~0.12, while the resistance coefficient of a regular globe valve is about 3.5~4.5. The opening and closing force is small. Gate valves are usually suitable for working conditions that do not require frequent opening and closing, and maintain the gate fully open or fully closed, and are not suitable for regulating or throttling use. And the flow resistance of the globe valve is large throughout the entire stroke, with a large imbalance force, and the required driving force or torque is correspondingly much greater. But it is very suitable for regulating and throttling fluids. For high-speed flowing media, when the gate is partially opened, it can cause valve vibration, which may damage the sealing surfaces of the gate and valve seat. Throttling can cause the gate to be eroded by the medium.
4. Different itineraries
The stroke of a gate valve is larger than that of a globe valve.
5. Different flow directions
When installing a shut-off valve, the medium can enter from below the valve core or from above. 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 and allow for the replacement of the packing when the pipeline in front of the valve is under pressure. The disadvantage of medium entering from below the valve core is that the driving torque of the valve is relatively high, about 1.05-1.08 times that of entering from above,