Check valve, also known as one-way valve or non-return valve, is used to prevent the backflow of fluid in pipelines. The bottom valve of a water pump is also considered as a check valve. The valve depends on the fluid to open or close in order to prevent backflow. It belongs to the category of active valves and is mainly used in pipelines where fluid only flows in one direction, in order to prevent accidents.
The check valve should not bear any force in the pipeline. The large check valve should be independently supported to prevent it from being affected by the pressure generated by the pipe system.
During installation, pay attention to the direction of fluid flow, which should be consistent with the direction of the arrow on the valve body.
The lift type straight flap check valve should be installed on a straight pipeline.
The lift type horizontal flap check valve should be installed on a horizontal pipeline. The principle of the check valve analysis is that it only allows fluid to flow in one direction, and blocks the flow in the opposite direction.
Generally, this type of valve is actively operated. Under the pressure generated by fluid flow in one direction, the valve flap opens. When the fluid flows in the opposite direction, the valve flap is closed by the fluid pressure and its own weight, which blocks the flow. The check valve belongs to this type of valve, which includes turning check valves and lift check valves. The turning check valve has a hinge structure, and a door-like valve flap is freely placed on the inclined valve seat surface. In order to ensure that the valve flap reaches the appropriate position on the valve seat surface every time, the valve flap is designed with a hinge structure, so that the valve flap has enough turning space and can completely touch the valve seat. The valve flap can be made entirely of metal, or it can be embedded with leather, rubber, or composite cover on the metal, depending on the application requirements.
With the turning check valve fully open, the fluid pressure is almost unobstructed, so the pressure drop through the valve is relatively small. The valve flap of the lift check valve is located on the valve seat sealing surface of the valve body. Except for the fact that the valve flap can move freely, the valve is similar to the gate valve. The fluid pressure makes the valve flap lift from the sealing surface of the valve seat, and the backflow of the medium makes the valve flap fall back onto the valve seat, which blocks the flow. Depending on the application conditions, the valve flap can be made entirely of metal, or in the form of rubber pads or rubber rings embedded on the valve flap support.
The check valve is used in pipeline systems to prevent backflow, prevent the pump and its driving motor from reversing, and prevent the release of medium from containers. The check valve can also be used in pipelines where the pressure can rise above the pressure of the main system to supply auxiliary system feed. Depending on the material used, the check valve can be used in pipelines for various media. When the check valve is installed in the pipeline, it becomes one of the fluid components of the complete pipeline system. The opening and closing process of the valve flap is affected by the transient flow condition of the system it is in, and the sealing characteristics of the valve flap also affect the flow condition of the fluid. The operating characteristics of the check valve are that the load changes greatly, the frequency of opening and closing is low, the application cycle is long without the need for moving parts, but when there is a need for "switching," it is necessary to move it sensitively, which is more demanding than the common mechanical movement.
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