Electric gate valve is a kind of valve that is widely used in pipelines, and it mainly plays the role of connecting and cutting off the medium. It is not suitable for adjusting the flow of the medium, but it can judge the flow according to the height of the valve stem (for example, the elastic seat gate valve for fire protection is equipped with an opening and closing scale). Compared with other valves, gate valves have a wider range of applications for pressure, temperature, diameter and other requirements.
Electric gate valve can be divided into: wedge type single gate type, elastic gate type, double gate type, parallel gate type according to different internal structures.
According to the difference of the valve stem bracket, it can be divided into: open stem gate valve and dark stem gate valve.
The main performance advantages of electric gate valve are:
1. The valve fluid resistance is small. Because the gate valve body is a straight-through type, the flow of the medium does not change the direction, so the flow resistance is smaller than other valves.
2. The sealing performance is better than that of the globe valve, and the opening and closing is more labor-saving than that of the globe valve.
3. Wide range of application, in addition to steam, oil and other media, it is also suitable for media containing granular solids and high viscosity, and is also suitable for venting valves and valves of low vacuum systems.
4. The gate valve is a valve with two flow directions, which is not limited by the flow direction of the medium, so it is suitable for pipelines where the medium may change the flow direction, and it is also easy to install.
The main performance disadvantages of electric gate valves are:
1. The shape design is high in size, and the opening and closing time is long. When opening, the valve plate needs to be lifted to the upper part of the valve cavity, and when closing, the valve plate needs to be completely dropped into the valve seat, so the opening and closing stroke of the valve plate is large and the time is long.
2. Due to the friction between the two sealing surfaces of the valve plate and the valve seat of the gate valve during the opening and closing process, the sealing surface is easily scratched, which affects the sealing performance and service life, and is not easy to maintain.
Performance comparison of several electric gate valves with different structures:
(1) Wedge type single gate electric gate valve
a. The structure is simpler than the elastic gate valve
b. At higher temperature, the sealing performance is not as good as that of elastic gate valve or double gate valve.
c. It is suitable for high temperature medium that is easy to coke.
(2) Elastic gate electric gate valve
a. It is a special form of wedge-type single gate valve. Compared with the wedge gate valve, the sealing performance is good at high temperature, and the gate plate is not easy to be stuck after being heated;
b. It is suitable for steam, high temperature oil and oil and gas medium, and is suitable for parts with frequent switching.
c. It is not suitable for media that is easy to coke.
(3) Double gate electric gate valve
a. The sealing performance is better than that of the wedge gate valve. When the inclination angle of the sealing surface and the valve seat are not very accurate, it still has good sealing performance.
b. After the sealing surface of the gate is worn, it can be used after replacing the metal pad at the bottom of the top center of the spherical surface. Generally, there is no need to surfacing and grinding the sealing surface, which is an advantage that the single gate and the elastic gate do not have.
c. It is suitable for steam, high temperature oil and oil and gas medium, and is suitable for parts with frequent switching.
d. It is not suitable for media that is easy to coke.
(4) Parallel electric gate valve
a. The sealing performance is worse than other forms of gate valves.
b. It is suitable for medium with low temperature and pressure.
c. The processing and maintenance of the sealing surface of the gate and the valve seat are simpler than other forms of gate valves.
The difference between the open rod electric gate valve and the dark rod electric gate valve:
The gate valve drives the opening and closing of the gate through the up and down lift of the valve stem. The drive thread of the rising stem gate valve is at the top of the valve stem bracket, so the opening and closing position of the gate can be judged by the position of the valve stem, and the drive thread is also convenient for daily lubrication and maintenance. , while not subject to fluid corrosion, the disadvantage is that the installation space is relatively large.
The transmission thread of the dark stem gate valve is inside the valve body, which saves the space of the valve stem bracket, so the height of the whole valve is reduced. If it is necessary to clarify the opening and closing position, an opening and closing scale can be installed on the top of the valve cover, which is suitable for places with narrow spaces such as underground drains (such as underground gate valves), pipe trenches, or places with high dust content.
Gate valves can also be divided into different gate valve types according to different materials, different pressures, different seals, and different connection methods.