Check valve refers to a valve whose opening and closing part is a round valve disc and acts by its own weight and medium pressure to block the backflow of the medium. It is an automatic valve, also known as check valve, check valve, return valve or isolation valve. The motion mode of the valve disc is divided into lifting type and swinging type. Lift check valves are similar in structure to globe valves, except for the lack of a stem that drives the disc. Its main function is to prevent media backflow. The valve can be opened and closed automatically by the pressure of the flowing medium, without the need for external energy. When the medium flow direction is correct, the valve disc is pushed open and the medium flows smoothly. However, when the medium flows in the opposite direction, the valve disc will automatically close, preventing the medium from flowing back. This process ensures the correct flow direction of the medium and also protects the safety of the equipment. In addition, check valves have other important functions. It prevents the backflow of the media, thereby protecting the device from damage. At the same time, it can also prevent the pump and pipe to produce water hammer phenomenon, to ensure the stable operation of the system.
Working principle
The check valve can also be used to feed the auxiliary system where the pressure may rise above the system pressure. Check valves can be mainly divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis). The function of this type of valve is to allow the medium to flow in only one direction and to prevent the flow in the opposite direction. Usually this valve is automatic operation, under the action of fluid pressure flowing in one direction, the valve disc opens; When the fluid flows in the opposite direction, the fluid pressure and the self-coincidence valve disc act on the seat, thus cutting off the flow. The check valve belongs to this type of valve, which includes swing check valve and lift check valve. Swing check valves have a hinged mechanism and a door-like disc that rests freely on the inclined seat surface. To ensure that the disc reaches the proper position on the seat surface each time, the disc is designed in a hinged mechanism so that the disc has enough space to swing and allow the disc to make true, full contact with the seat. The disc can be made entirely of metal, or the metal can be inlaid with leather, rubber, or a synthetic cover, depending on the performance requirements. With the swing check valve fully open, the fluid pressure is virtually unimpeded, so the pressure drop through the valve is relatively small. The disc of the lift check valve is located on the seat sealing surface of the valve body. In addition to the valve disc can be lifted freely, the rest of the valve is like a globe valve, fluid pressure causes the valve disc to lift from the seat sealing surface, and the media backflow causes the valve disc to fall back to the seat and cut off the flow. Depending on the conditions of use, the disc can be an all-metal structure, or it can be in the form of a rubber pad or rubber ring mounted on the disc holder. Like the globe valve, the passage of fluid through the lift check valve is narrow, so the pressure drop through the lift check valve is greater than that of the swing check valve, and the flow rate of the swing check valve is less restricted.
Structural classification
- Lift check valve is divided into vertical and horizontal two kinds
- Swing check valve is divided into single disc type, double disc type and multi-disc type
- Butterfly check valve is straight through
Material classification
1.Cast iron
2.Brass
3.Stainless Steel
4.Carbon steel
5.Forged steel
Install
We first ensure that the check valve is mounted on the horizontal line and that the fluid direction is consistent with the direction indicated by the body. For vertical pipes, the disc should be open to prevent media backflow. There are two installation methods: flange connection and threaded connection. When installing, pay attention to torque control to avoid too tight or too loose. After installation, check whether the check valve is firm, no leakage phenomenon, and confirm that the valve disc is flexible to open and close. The correct installation and inspection can ensure the normal operation of the check valve and play its maximum role.
Matters needing attention
- Do not let the check valve bear weight in the pipeline system, and the large check valve should be independently supported so that it is not affected by the pressure of the pipeline system.
- When installing, pay attention to the direction of the medium flow should be consistent with the direction of the arrow marked on the valve body.
