Among many valve products, gate valves, butterfly valves, and ball valves are all very commonly used valve types. However, many users do not know how to choose because they do not know the differences between them when selecting models.
Through this article, you will learn the structural principles, advantages and disadvantages of these types of valves. Finally, combined with Wesdom’s 25 years of valve experience, in-depth analysis will allow you to easily choose a more suitable valve according to different situations.
Gate valve is one of the most common opening and closing valves, which uses a gate plate (i.e. opening and closing parts, in which the opening and closing parts are called gate plates or gates, and the gate seats are called gate plate seats) to connect (fully open) or Cut off (fully close) the medium in the pipeline.
It is not allowed to be used as a flow interceptor. During use, you should avoid opening the gate a small amount, because the erosion of the high-speed flowing medium will accelerate the damage of the sealing surface.
The gate plate moves up and down on one side perpendicular to the center line of the gate seat channel, cutting off the medium in the pipeline like a gate, so it is called a gate valve.
Advantages of gate valves:
①The fluid resistance is small.
②The external force required for opening and closing is small.
③The flow direction of the medium is not restricted.
④When fully open, the sealing surface is less eroded by the working medium than the stop valve.
⑤The body shape is relatively simple and the casting process is good.
Disadvantages of gate valves:
①The overall dimensions and opening height are both large. The installation requires a large space.
②During the opening and closing process, there is relative friction between the sealing surfaces, which can easily cause scratches.
③Gate valves generally have two sealing surfaces, which adds some difficulties to processing, grinding and maintenance.
Butterfly valve refers to a valve whose closing part (valve disc or butterfly plate) is a disc and rotates around the valve axis to open and close. It mainly serves to cut off and throttle the pipeline.
The butterfly valve opening and closing part is a disc-shaped butterfly plate that rotates around its own axis in the valve body to achieve the purpose of opening and closing or adjustment. The angle from fully open to fully closed of a butterfly valve is usually less than 90°. The butterfly valve and butterfly rod themselves do not have self-locking capabilities. In order to position the butterfly plate, a worm gear reducer must be installed on the valve rod. The use of worm gear reducer not only makes the butterfly plate self-locking, allowing the butterfly plate to stop at any position, but also improves the operating performance of the valve.
Advantages of butterfly valve:
① Opening and closing is convenient, fast, labor-saving, has small fluid resistance, and can be operated frequently.
②Simple structure, small dimensions, short structural length, small volume, light weight, suitable for large diameter valves.
③ Mud can be transported with minimal liquid accumulation at the pipe mouth.
④Under low pressure, good sealing can be achieved.
⑤Good adjustment performance.
⑥When fully open, the effective circulation area of the valve seat channel is larger and the fluid resistance is smaller.
⑦The opening and closing torque is small. Since the butterfly plates on both sides of the rotating shaft are basically equally affected by the medium and the torque is generated in opposite directions, opening and closing is less labor-intensive.
⑧The sealing surface material is generally made of rubber or plastic, so the low-pressure sealing performance is good.
Disadvantages of butterfly valve:
①The operating pressure and operating temperature range are small.
②Poor sealing.
The working principle of the ball valve is to rotate the valve core to open or block the valve. Ball valves are light on and off, small in size, can be made into large diameters, have reliable sealing, simple structure, and easy maintenance. The sealing surface and spherical surface are always in a closed state and are not easily eroded by the medium. They are widely used in various industries.
The ball valve and the plug valve belong to the same type of valve, only its closing part is a ball, and the ball rotates around the center line of the valve body to open and close. Ball valves are mainly used in pipelines to cut off, distribute and change the flow direction of media.
Ball valves have the following advantages:
①The fluid resistance is small, and the full-diameter ball valve has basically no flow resistance.
②Simple structure, small size and light weight.
③Tight and reliable. It has two sealing surfaces, and the sealing surface materials of ball valves currently use various plastics, which have good sealing properties and can achieve complete sealing. It has also been widely used in vacuum systems.
④Easy to operate, quick to open and close, just rotate 90° from fully open to fully closed, convenient for long-distance control. 5． It is easy to maintain. The ball valve has a simple structure and the sealing ring is generally movable, making it easy to disassemble and replace. 6. When fully open or fully closed, the sealing surfaces of the ball and valve seat are isolated from the medium. When the medium passes, it will not cause erosion of the valve sealing surface.
⑤Wide range of application, diameter ranging from a few millimeters to several meters, and can be applied from high vacuum to high pressure. 8. Since the ball valve has wiping properties during the opening and closing process, it can be used in media with suspended solid particles.
Disadvantages of ball valves:
①High processing precision and relatively high cost
②Difficult to use at high temperatures
Summarize:
* The gate valve is a straight-stroke valve, that is, the valve stem drives the valve plate to move vertically up and down to complete the opening and closing of the gate valve. Therefore, the flow resistance of the gate valve is small, but because of its high opening height, the opening and closing speed is slow.
* Butterfly valves and ball valves are quarter-turn valves, that is, the valve plate of the butterfly valve rotates 90° around the valve axis to complete the opening and closing action of the butterfly valve. Therefore, the opening height of the butterfly valve is only one-quarter of the channel diameter, so it opens and closes quickly.
* The gate valve has small flow resistance and good sealing performance, because the gate valve plate and the flow direction of the medium are at a perpendicular angle. If the gate valve does not open and close the valve plate in place, the medium’s erosion of the valve plate will cause the valve plate to vibrate, which can easily cause damage to the gate valve seal. Therefore, it is mostly used as a cut-off in pipelines that require strict sealing and do not require frequent opening and closing, but are not suitable for adjusting pipeline media parameters.
* Due to its slow opening and closing speed, the gate valve is not suitable for emergency shut-off situations.
* The butterfly valve not only has a cut-off function, but also has a regulating function. The butterfly valve opens and closes quickly and can be opened and closed frequently. It is especially suitable for occasions that require quick opening or shutoff.
* Compared with gate valves, butterfly valves are small in size and light in weight. In some working conditions with limited installation space, you can choose wafer-type butterfly valves to save more space.
* Butterfly valves can be made into large diameters, and butterfly valves above DN300 are commonly used. The price of butterfly valves of the same caliber is much lower than that of gate valves.
* The ball valve has wiping properties during the opening and closing process, so it can be used in media with suspended solid particles.
* Ball valves have small fluid resistance, and full-bore ball valves have basically no flow resistance.
* If the diameter of the passage in a valve body is different (often the diameter at the valve seat is smaller than the diameter at the flange connection), it is called diameter contraction.
* Diameter shrinkage can reduce the size of parts, correspondingly reduce the force required for opening and closing, and at the same time expand the application range of parts. But after the diameter shrinks. Fluid resistance loss increases.
* Under certain working conditions in some sectors (such as oil pipelines in the petroleum sector), valves with reduced diameter are not allowed. On the one hand, this is to reduce the resistance loss of the pipeline, and on the other hand, it is to prevent the diameter shrinkage from causing obstacles to the mechanical cleaning pipeline.
