The difference between ball valve and gate valve
1. Disc structure
The disc of the ball valve is a ball. Due to the structure of the fixed ball, the valve ball is fixed under high pressure, especially in the closed state, and the upper valve stem and the lower support shaft bear part of the pressure from the medium, so The valve ball does not offset downstream, so the pressure on the downstream valve seat is relatively small, so the friction force that the valve overcomes when acting is small, the valve seat wear is small, service life of ball valve is long, especially for valves that operate frequently. The fixed structure is more suitable.
The disc of gate valve is a wedge-shaped valve plate or parallel valve plate. The lower part has no fulcrum. Therefore, when the valve is under high pressure application and in the closed state, the valve disc bears a great pressure from the medium, and due to its flat valve disc structure, all the medium pressure acts on the valve disc at the same time, then the valve disc will press to the downstream valve seat (at the same time, excessive pressure acts on the vertical surface of the valve disc, which will cause the valve plate to be deformed to a certain extent, whether it is a wedge or parallel double gate), then the valve is opened. When a great friction force needs to beovercome, the wear of the valve seat will result in a short life of the valve.
2. Valve seat structure
There is a spring inside ball valve seat, and the sealing design of the valve seat makes it difficult for the dregs 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. When the valve moves, the valve seat has a certain scraper function, which can scrape off the dross attached to the valve core after long-term operation, which can ensure the sealing performance of the valve for a long time. Especially in the application of high temperature and high pressure, due to the selection of the material of the valve seat, valve body and valve ball with the same thermal expansion coefficient, as well as the valve seat of the spring structure, when the valve is closed, there is a huge temperature difference and temperature drop, it 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 flow, so the valve seat will be compressed, resulting in a large pressing force on the valve plate. When the valve is opened again, a large torque is required to overcome this pressing force, which will cause great damage to the valve seat and affect valve seat life. 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 noise3. Itinerary
The stroke of the ball valve is an 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. Actuator
Due to the fixed ball design, the opening and closing torque of the ball valve is small, so the actuator is correspondingly small.
Due to the large pressing force of the valve disc on the valve seat, the gate valve needs a large torque to overcome this large friction force, and the actuator is equipped with a large amount.
5. Maintenance
Ball valves generally do not need maintenance, especially the valve ball and valve seat, due to small wear, it does not need to be replaced within 5 years.
Due to the large wear of the valve seat, the gate valve needs regular maintenance.
