The differences between ball valves and gate valves

1. Disc structure

The valve disc of the ball valve is a ball, because of its fixed ball structure, the valve ball is fixed under high pressure conditions, especially in the closed state, the upper stem and the lower support shaft decompose part of the pressure from the medium, so the valve ball does not migrate downstream, so the downstream valve seat is under relatively small pressure, so the valve valve in the operation to overcome the friction is small, then the valve seat wear is small. The service life of the valve is long, especially for the valve with frequent action, this structure is more suitable.

The disc of gate valve is wedge valve disc or parallel valve disc. Its lower part has no supporting shaft. Therefore, when the valve is under high pressure application and in the closed state, the valve disc bears great pressure from the medium, and because of its flat valve disc structure, all the medium pressure acts on the valve disc at the same time, the valve plate will be pressed to the downstream valve seat (At the same time, excessive pressure acts on the vertical surface of the valve disc, it will make the valve disc whether it is a wedge or a parallel double gate). There will be a certain deformation), then the valve needs to overcome great friction when opened, then the wear of the valve seat prints the life of this valve is short.

2. Valve seat structure

The valve seat has a spring inside, and the sealing design of the seat part makes it difficult for the slag in the medium to enter the seat. The valve seat is in long-term contact with the valve ball under the action of the spring, and when the valve is operated, the valve seat has a certain scraper effect, which can scrape off the dregs attached to the valve disc after long-term operation, which can ensure the sealing performance of the valve for a long time. Especially in high temperature and high pressure applications, because the material of the valve seat, valve body, valve ball is selected with the same thermal expansion coefficient, and the valve seat of the spring structure, when the valve is closed, the huge temperature difference and temperature drop will not affect the action of the valve, and the valve will not produce the phenomenon of locking.

Gate valve seat is very narrow, in high temperature applications, when the valve is closed, because the medium does not flow, so the temperature drops, then the seat will tighten, resulting in a large compression force on the valve plate. When the valve is opened again, a large torque is needed to overcome this compression force, which will cause great damage to the seat and affect the life of the seat. Thus, the service life of the valve is affected. In addition, due to the weight of the gate itself when the valve is closed, it will bring a lot of impact force to the valve and make a lot of noise.

3. Route

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

4. Executive agencies

Ball valve due to the fixed ball design, its opening and closing torque value is small, so the actuator is correspondingly small. Gate valve because the valve plate on the seat of the pressing force is large, so to overcome this large friction requires a great torque, then the actuator with large.

5. Maintenance

Ball valves generally do not need maintenance, especially the ball and seat, due to small wear, generally do not need to be replaced within 5 years. Gate valve needs regular maintenance due to the large wear of the seat.