A Comprehensive Comparison of Butterfly Valves and Gate Valves

Butterfly valves and gate valves are both common and important valve types in piping systems. Although they have some similarities in appearance and function, there are significant differences in many aspects such as working principle, structural design, flow characteristics and application range. This article will elaborate on the differences between butterfly valves and gate valves to help readers better understand the respective characteristics of the two valves and their application scenarios.

Differences in Work Methods

Butterfly valve, also known as flap valve, is a simple structure of the regulating valve, widely used in low pressure pipeline medium switching and flow regulation. The main role of the butterfly valve is to cut off and throttle the medium, and the opening and closing process is achieved by rotating a disc similar to the butterfly wing (that is, the butterfly plate) around its central axis, usually the rotation Angle is less than 90°. Because the butterfly valve and the butterfly valve stem themselves do not have self-locking ability, in practical applications, in order to position the butterfly plate, it is usually necessary to install a worm gear reducer on the valve stem. The use of worm gear reducer not only gives the control plate self-locking function, so that the control plate can stay in any position, but also significantly improves the operating performance of the valve and reduces the difficulty of operation.

Gate valves work on a completely different principle. The gate valve controls the flow of the medium through the up and down movement of the valve plate (that is, the gate plate), and the movement direction of the gate plate is perpendicular to the flow direction of the fluid. Gate valve can only be in a fully open or fully closed state, mainly used for cutting off the medium in the pipeline, so it is not suitable for flow regulation. Gate valves are mostly forced seals, that is, when the valve is closed, the gate plate must be tightly pressed on the seat by an external force to ensure the tightness of the sealing surface and prevent media leakage.

Differences in Structural Design

The main components of the butterfly valve include the valve body, the butterfly plate, the valve stem, the sealing ring and the transmission device. The body is usually cylindrical with cylindrical bumps in the upper and lower part for mounting the stem. The butterfly valve is usually connected to the pipe through a flange connection, and if the clamp connection is used, the structural length is smaller and the installation is more convenient. The butterfly plate is the opening and closing part of the butterfly valve, and the valve stem is the rotating shaft of the butterfly plate, which is sealed by the packing box to prevent the leakage of the medium. The upper end of the stem is directly connected to the drive to transfer torque, allowing the butterfly plate to open and close quickly and precisely.

The structure of gate valve is relatively more complex, usually composed of valve body, seat, stem, gate, valve cover, sealing ring and other parts. The connection between the valve body and the pipeline is also varied, including flange connection, welding connection, etc. As the core opening and closing part of gate valve, the gate plate directly determines the sealing performance of the valve. The stem is connected to the gate, and the up and down movement of the gate is controlled by rotating the hand wheel or other transmission device. Due to the extensibility of the gate valve structure, it can also be transformed into an electric gate valve or a pneumatic gate valve by being equipped with different transmission devices to meet the needs of different working conditions.

Differences in Flow Characteristics and Application Range

In terms of flow characteristics, the gate valve, due to its special design, has the characteristics of low fluid resistance and good sealing performance, so it is particularly suitable for pipeline systems that need to be tightly closed. After closing, the sealing performance is good, and the internal leakage is less, which ensures the complete partition of the medium. However, gate valves are not suitable for flow regulation, so their application is limited in situations where precise flow control is required. In general, gate valves are widely used in trunk pipelines to completely cut off or switch on fluid.

Butterfly valves are more diverse in terms of flow characteristics. The butterfly valve is not only small in size and light in weight, but also integrates the advantages of the globe valve and the ball valve, and can be designed with different flow characteristics by adjusting the shape of the butterfly plate. Therefore, butterfly valves can not only be used for switching control of pipelines, but also for flow regulation. At the same time, the closing performance of the butterfly valve is also better, and because of its compact body structure, it is suitable for large-caliber pipeline systems. Therefore, the application range of butterfly valves is very wide, from water supply systems, cooling water systems to gas transmission systems, are widely used. In addition, butterfly valve can also withstand high temperature and high pressure, especially suitable for conveying a variety of corrosive and non-corrosive fluid media, widely used in power generation, environmental protection, chemical industry, smelting and other engineering systems.

From the practical application of engineering, in the water supply network, in order to reduce the depth of the soil cover of the pipeline, the butterfly valve is usually preferred in the pipeline of larger caliber. If the depth of soil cover has little effect on the project, the gate valve is chosen for its better sealing performance. However, it should be noted that the price of gate valves of the same specification is usually higher than that of butterfly valves, so the balance between cost and performance needs to be considered comprehensively in practical applications. Although the butterfly valve has certain advantages in installation and operation, from the use of the past ten years, the failure rate of the butterfly valve is still higher than that of the gate valve. Therefore, if conditions permit, expanding the scope of use of gate valves, especially in the need for higher sealing and reliability, is worth paying attention to.

Different Requirements for Installation and Maintenance

The installation and maintenance of gate valves need to follow a series of strict operating codes. First of all, the handwheel, handle and transmission mechanism shall not be used to lift the valve, and collision is strictly prohibited during installation to avoid damage to the valve. The double gate valve should be installed vertically, that is, the stem is in a vertical position and the handwheel is at the top to ensure smooth opening and closing operation. For gate valves equipped with bypass valves, the bypass valve should be opened before opening the main valve to balance the pressure difference between the inlet and outlet, reduce the opening force, and reduce the impact on the gate and sealing surface. Gate valves with transmission mechanisms shall be installed in accordance with the specifications of the product. In addition, if the gate valve is used frequently, it needs to be lubricated at least once a month to ensure the normal operation of the transmission mechanism and the service life of the valve.

Butterfly valve installation and maintenance is relatively simple. When installing, ensure that the disc is in the closed position to avoid damage to the disc. The opening position of the butterfly plate should be determined according to its rotation Angle, and confirm whether the rotation range of the butterfly plate will be limited by pipes or other equipment before installation. For butterfly valves with bypass valves, the bypass valve should be opened before installation to ensure the smooth flow of the medium and reduce the resistance of the valve when opening and closing. During the installation process, it should be operated in accordance with the manufacturer's installation instructions, especially for the butterfly valve with a large weight, the installation should ensure that there is a strong foundation support to avoid the displacement or vibration of the valve during use, which will affect its normal work.

Conclusion

In general, butterfly valves and gate valves have their own characteristics in engineering applications. With its compact structure, easy operation and flexible flow regulation, butterfly valves have been widely used in various pipeline systems, especially in large diameter pipelines and high temperature and pressure environments. The gate valve, with its excellent sealing performance and small fluid resistance, is more suitable for occasions where the medium flow needs to be completely cut off. Which valve to choose should be determined according to the specific engineering requirements, medium characteristics and economy. In practical application, the efficient and safe operation of pipeline system can be ensured by reasonable selection and correct maintenance of these two valves.