Classification and installation direction of check valves
Overview of check valve
Check valves are an important fluid control device, widely used in water conservancy projects, petrochemicals, environmental protection and other fields. Its main function is to prevent the backflow of media and ensure the one-way flow of media in the pipeline system. The classification and installation direction of check valves directly affect their performance and service life. This article will introduce the different types of check valves and the considerations for their installation directions in detail.
Main types of check valves
According to the structure and working principle, check valves are mainly divided into the following types:
1. Double plate check valve
2. Lift check valve
3. Ball check valve
4. Swing check valve
Installation direction type of check valve
1. Horizontal installation: refers to the method of installing the check valve on a horizontal pipeline, which is often used in low-pressure pipeline systems, and the diameter of the valve flap is larger than the diameter of the pipeline.
2. Vertical installation: refers to the method of installing the check valve on a vertical pipeline, which is often used in high-pressure pipeline systems, and the diameter of the valve flap is smaller than the diameter of the pipeline.
1. Double-disc check valve
Dual disc check valve: usually consist of two semicircular discs that move around the stem perpendicular to the centerline of the fluid flow. Double-disc check valves are compact valves with a small length. They are installed between two flanges. They are generally clamped or flanged. They are generally used in pipes with a diameter of ≤1200mm.
Installation direction of Double-disc check valve
Double-disc check valves can be installed horizontally or vertically in the pipeline. Horizontal installation can make the opening and closing of the check valve affected by gravity, making its opening speed more stable and effectively reducing pipeline pressure loss. Vertical installation can make the valve affected by gravity when closed, making its seal tighter. In addition, vertical installation can prevent the check valve disc from vibrating rapidly during the rapid change of the fluid, reduce the vibration wear of the disc and the valve seat, and extend the service life of the valve.
2. Swing check valve
Swing check valves have a valve disc. When the medium flows forward, the valve disc is pushed open; when the medium flows in the reverse direction, the valve disc is snapped back onto the valve seat to prevent backflow. This type of valve is often used in large-diameter pipelines because of its simple structure and low resistance.
Installation direction of Swing check valve
Swing check valves can be installed horizontally or vertically, but it is generally recommended to be installed in horizontal pipelines. It should be noted that, depending on the actual situation, the swing check valve can also be installed obliquely, as long as the installation angle does not exceed 45 degrees and the installation position is appropriate, it will not affect the normal opening and closing functions of the valve.
3. Horizontal lift check valve
The valve disc of the horizontal lift check valve moves up and down along the guide rail in the valve body. When the medium flows forward, the valve disc is lifted; when the medium flows in the reverse direction, the valve disc falls back to the valve seat to prevent backflow.
Installation direction of Horizontal lift check valve
The horizontal lift check valve must be installed on a horizontal pipeline. Because when installed vertically, its valve core is in a horizontal state, its centering performance with the valve seat decreases under its own weight, affecting the sealing performance of the valve core.
4. Vertical lift check valve
For vertical lift check valves, the movement direction of the valve core is parallel to the pipeline direction. And the center of the valve core coincides with the center of the flow channel.
Installation direction of Vertical lift check valve
Vertical check valves must be installed vertically in pipes where the medium flows upward, because gravity helps the valve disc close quickly when the flow stops.
5. Ball check valve
A ball check valve uses a ball that moves up and down in the valve body. When the medium flows forward, the ball is pushed away from the valve seat, the channel opens, and the medium passes; when the medium flows in the reverse direction, the ball returns to the valve seat to prevent backflow.
Installation direction of Ball check valve
Ball check valves can be installed on horizontal pipes, but are more suitable for vertical installation, especially when the medium flows upward. The dead weight of the ball helps the valve seal when the flow stops.
Factors affecting vertical installation of check valve
When installing a check valve vertically, several factors need to be considered to ensure its effective operation:
1. Flow direction
In vertical installation, the flow direction of the medium is crucial. When flowing upward, the valve disc can be opened by the pressure of the medium, and closing is gravity that helps the valve disc return to its position, while when flowing downward, additional measures may be required to ensure that the valve closes reliably.
2. Gravity effect
Gravity affects the opening and closing of the valve. Valves that rely on gravity to seal, such as double-plate and lift check valves, work better when flowing vertically upward.
3. Media characteristics
The characteristics of the media, such as viscosity, density, and particle content, affect the performance of the valve. Viscous or particle-containing media may require a stronger design and frequent maintenance to ensure reliable operation of the valve.
4. Installation environment
The installation environment, including temperature, pressure, and the presence of corrosive substances, will affect the performance and life of the valve. Selecting materials and designs suitable for a specific environment can extend the service life of the valve.
Advantages of vertical installation of check valve
1. Utilization of gravity
In the case of upward flow of the media, gravity helps the valve to close, improves the sealing performance, and does not require external assistance.
2. Reduce wear
Using the gravity of the media and the valve plate to close the check valve can reduce vibration, reduce wear, extend the service life of the valve, and reduce the frequency of maintenance.
Disadvantages of vertical installation of check valve
1. Flow resistance
Vertical installation may increase flow resistance, especially for vertical lift check valves, which need to resist not only the weight of the valve plate, but also the pressure given by the spring above the valve plate. This will lead to reduced flow and increased energy consumption.
2. Water hammer phenomenon
When the medium flows upward, the force of the check valve and the gravity of the medium will increase the pressure in the pipeline, making it easier to cause water hammer phenomenon.