Difference between ball valve and gate valve

1. Working principle

Ball valve: the opening and closing member (ball) is driven by the valve stem and rotates around the ball valve axis. Ball valve in the pipeline is mainly used to do cut off, distribution and change the direction of media flow, it only needs to rotate 90 degrees of operation and a very small torque to close tightly. Ball valve is most suitable for use as a switch, cut-off valve, V ball valve.

Gate valve: the opening and closing member is the gate, the direction of movement of the gate is perpendicular to the direction of the fluid, the gate valve can only be fully open and fully closed, not for regulation and throttling. The gate valve is sealed by contact between the seat and the gate, usually the sealing surface will be welded metal materials to increase wear resistance, such as welded, stainless steel, etc.. The gate has rigid gate and resilient gate, according to the different gate, the gate valve is divided into rigid gate and resilient gate valve.

2. Spool structure

Ball valve spool for the sphere, due to its fixed ball structure, so that the valve in high pressure conditions, especially in the closed state, the ball is fixed, the upper stem and the lower branch shaft decomposition of part of the pressure from the medium, so the ball does not shift downstream, so the downstream seat pressure is relatively small, so the valve in action to overcome the friction is small, the seat wear is small, the valve long service life, especially This structure is more suitable for valves with frequent action.

The gate valve spool is a wedge-shaped plate or parallel plate. The lower part of the valve has no pivot. Therefore, the valve in high-pressure applications, and in the closed state, the valve plate is subjected to great pressure from the medium, and because of its flat plate structure, so that all the medium pressure at the same time on the valve plate, the valve plate will be dead to the downstream seat (while excessive pressure on the vertical surface of the valve plate, will make the valve plate whether wedge or parallel double gate, there will be a certain deformation), the valve in the Need to overcome great friction when opening, then the wear and tear of the valve seat prints the short life of this valve.

3. Features

Ball valve: wear-resistant; good sealing performance; because the seal of the hard seal ball valve is artificially ground until the spool and the seal completely fit to use. So his sealing performance is reliable; light switching; because the bottom of the seal ring of the hard seal ball valve uses a spring to make the seal ring and the spool hold tightly together, so the switch is very light when the external force exceeds the preload of the spring; long service life.

Gate valve: compact structure, smooth passage, small number of flow resistance, stainless steel and hard alloy used for sealing surface, long service life, PTFE packing. Reliable sealing. Light and flexible operation.

4. Stroke

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

5. Actuator

The ball valve has a small torque value for opening and closing due to the fixed ball design, so the actuator is matched with a small size accordingly. The gate valve requires a large torque to overcome the large frictional force due to the large compression force of the valve plate on the valve seat, so the actuator is equipped with a large torque.

6. Maintenance

Ball valves generally do not require maintenance, especially the valve ball and seat, due to small wear, generally within 5 years without replacement. Gate valve requires regular maintenance due to the large wear of the valve seat.