The difference between ball valve and gate valve

1. Differences in spool structure

1. The valve core of the ball valve is a sphere. Due to the structure of the fixed ball, the valve ball is fixed under high pressure conditions, especially in the closed state, and the upper valve stem and the lower support shaft decompose part of the pressure from the medium. , so the valve ball does not deflect downstream, so the pressure on the downstream valve seat is relatively small, so the friction force overcome by the valve when it moves is small, the wear of the valve seat is small, and the service life of the valve is long, especially for frequent movements. Valve, this structure is more suitable.

2. The spool of the gate valve is a wedge-shaped valve plate or a parallel valve plate. Its lower part has no support shaft. Therefore, when the valve is under high pressure application and in the closed state, the valve plate bears a great pressure from the medium, and because of its flat valve plate structure, all the medium pressure acts on the valve plate at the same time, the valve plate It will be firmly pressed to the downstream valve seat (at the same time, excessive pressure acts on the vertical surface of the valve plate, which will make the valve plate deform to a certain extent whether it is wedge-shaped or parallel double gate), then the valve will open When it is necessary to overcome the great friction, the wear of the valve seat will print the short life of the valve.

2. Differences in valve seat structure

There is a spring inside the valve seat of the ball valve, and the sealing design of the valve seat makes it difficult for the dross in the medium to enter the valve seat. The valve seat is in contact with the valve ball for a long time under the action of the spring, so when the valve operates, the valve seat has a certain scraper effect, which can scrape off the dross attached to the valve core after long-term operation, so the valve can be guaranteed for a long time. Sealing performance. Especially in the application of high temperature and high pressure, because the materials of the valve seat, valve body and valve ball are selected with the same thermal expansion coefficient and the valve seat with spring structure, when the valve is closed, the huge temperature difference and temperature The drop will not affect the action of the valve, and the valve will not lock up. The valve seat of the gate valve is very narrow. In high temperature applications, when the valve is closed, the temperature drops because the medium does not circulate, so the valve seat will shrink, which will generate a large pressing force on the valve plate. When opening the valve again, it is necessary to overcome this pressing force with a large torque, which will cause great damage to the valve seat and affect the life of the valve seat. Thus affecting the service life of the valve. In addition, due to the self-weight of the gate itself when the valve is closed, it will bring a great impact to the valve and cause a lot of noise.

3. Differences in itinerary

The stroke of the ball valve is angular stroke, so the installation space is small and the height is low. The stroke of the gate valve is a straight stroke, so the installation space is large and the height is high.

4, the difference between the executive body

Due to the design of the fixed ball, the torque value of its opening and closing is small, so the actuator is correspondingly small. Since the pressing force of the valve plate on the valve seat is large, a huge torque is required to overcome this large friction force, so the actuator is equipped with a large one.

5, the difference in the flow direction of the medium

The ball valve is of double flow direction, so there is no installation flow problem on site. Gate valves are generally unidirectional.

6, the difference in maintenance

Generally, no maintenance is required, especially the valve ball and valve seat, due to the small wear and tear, generally no need to be replaced within 5 years. Due to the large wear of the valve seat, the gate valve needs regular maintenance.